From Many Worlds: “NExSS 2.0”

NASA NExSS

From Many Worlds

May 13, 2019
Marc Kaufman

Finding new worlds can be an individual effort, a team effort, an institutional effort. The same can be said for characterizing exoplanets and understanding how they are affected by their suns and other planets in their solar systems. When it comes to the search for possible life on exoplanets, the questions and challenges are too great for anything but a community. NASA’s NExSS initiative has been an effort to help organize, cross-fertilize and promote that community. This artist’s concept Kepler-47, the first two-star systems with multiple planets orbiting the two suns, suggests just how difficult the road ahead will be. ( NASA/JPL-Caltech/T. Pyle)

The Nexus for Exoplanet System Science, or “NExSS,” began four years ago as a NASA initiative to bring together a wide range of scientists involved generally in the search for life on planets outside our solar system.

With teams from seventeen academic and NASA centers, NExSS was founded on the conviction that this search needed scientists from a range of disciplines working in collaboration to address the basic questions of the fast-growing field.

Among the key goals: to investigate just how different, or how similar, different exoplanets are from each other; to determine what components are present on particular exoplanets and especially in their atmospheres (if they have one); to learn how the stars and neighboring exoplanets interact to support (or not support) the potential of life; to better understand how the initial formation of planets affects habitability, and what role climate plays as well.

Then there’s the question that all the others feed in to: what might scientists look for in terms of signatures of life on distant planets?

Not questions that can be answered alone by the often “stove-piped” science disciplines — where a scientist knows his or her astrophysics or geology or geochemistry very well, but is uncomfortable and unschooled in how other disciplines might be essential to understanding the big questions of exoplanets.

The original NExSS team was selected from groups that had won NASA grants and might want to collaborate with other scientists with overlapping interests and goals but often from different disciplines. (NASA)

The original idea for this kind of interdisciplinary group came out of NASA’s Astrobiology Program, and especially from NASA astrobiology director Mary Voytek and colleague Shawn Domogal-Goldman. It was something of a gamble, since scientists who joined would essentially volunteer their time and work and would be asked to collaborate with other scientists in often new ways.

But over the past four years NExSS has proven itself to be very active and useful in terms of laying out strategies for tackling the biggest questions in the field of exoplanets and whether they might harbor life. In two major reports last year, the private, congressionally-mandated National Academies of Sciences, Engineering and Medicine held up NExSS as a successful model for moving the science forward.

One of the study co-chairs, David Charbonneau of Harvard University, said after the release of the study that the “promise of NExSS is tremendous…We really want that idea to grow and have a huge impact.”

This major report from the National Academy of Sciences last year endorsed NExSS as a program that substantially aided the exoplanet community. The report recommended that the organization be expanded. (NAS)

So with that kind of affirmation, it was hardly surprising that the first gathering of a newly constituted NExSS at the University of California, Santa Cruz featured 34 teams, double the original 17. (The team members, both new and original, are here.)

As explained at the opening of the gathering by Voytek and others, the NExSS approach is all about creating, expanding and promoting the fast-growing fields of exoplanet habitability and astrobiology more generally.

“The original NExSS members were in service to all of you,” she told the group. “They provided the opportunity to help your community to push questions further and also to get NASA headquarters to give some necessary attention to what you are doing.”

And in many ways they succeeded. The NExSS teams may not have gotten funded additionally for their work, but the group’s rising profile created important advisory opportunities for participants.

From the first NExSS groups, for instance, scientists were selected for leadership roles in the main exoplanet science group and several for science and technology definition teams. These groups established by NASA are putting together four proposals for a grand observatory for the 2030s — a hoped-for successor to the Hubble Space Telescope and the James Webb Space Telescope.

NExSS members also were called on to organize in-depth workshops on subjects ranging from defining and interpreting biosignatures on distant planets, to the centrality of exoplanet interiors and most recently to what signs of advanced technological civilizations might be detectable. Major white papers were generally written, submitted and published in journals following these NExSS workshops.

“I think putting together NExSS is most successful thing I’ve done in my career in NASA,” said Voytek who, in her decade-plus at the agency, has worked to change attitudes about astrobiology and interdisciplinary work. “I’m proud of what you did and we did.”

What’s more, as Voytek explained at the beginning of the meeting, the NExSS approach will spread with the creation of four new networking groups based on the model of NExSS.

They will use the same cross-disciplinary, get-to-know-your-fellow scientists approach to jump-start collaborations and cross-fertilizing in other aspects of the search for life beyond Earth, as well as the effort to understand how life on Earth (and potentially elsewhere) might have started and grown more complex.

(The four, below, focus on planetary chemistry before life, on biosignatures, on the transition from early single cell organisms to more complex ones, and on what can be learned from ocean worlds.)

This expansion, which will be part of a reorganization of NASA’s astrobiology program, will change the way that science teams will be funded and also, as Voytek put it, would “democratize” the process that NExSS began. The original program had selected many of its principal investigators from large teams and organizations, but the expanded NExSS and the four other groups to come will be more widely open to teams and individuals from smaller institutions who are earlier in their careers.

This is important, Voytek and other NExSS organizers said, because the NExSS approach allows scientists to network in ways that create science opportunities, as well as those avenues into the major prioritizing organizations in their exoplanet/astrobiology community writ large.

One value of this approach can be seen in the person of planetary scientist Sarah Morrison, a postdoc at the large Pennsylvania State University exoplanet program who has been hired to teach at the much smaller Missouri State University program.

She is a co-principal investigator on one of two NExSS teams at Penn State and was at last week’s Santa Cruz meeting in that capacity.

Her research focuses on protoplanetary disks and planet formation within them. In particular, she studies the many different types of interactions — collisions, migrations, atmosphere losses — that forming planets can have within their natal disks. She is also intrigued by solar systems where the planets orbit in resonance to each other.

These factors, and many others, have implications for the composition of planets and then for the possibility of life starting on them. Factors such as the eccentricity of a planet’s orbit or where it was formed within the disk can make a planet a good candidate for habitability or one where life is impossible.

For Morrison, NExSS is an avenue for keeping her research vibrant.

“I’m going to a smaller institution, with not so many people doing exoplanets,” she told me. “For me to remain active in the field and work, and to have the collaborators I need to open possibilities for students working with me, this type of network can be very important – on the research side and education side.”

She said that it isn’t always easy to find scientists whose work overlaps with hers, but that at the NExSS meeting it was easy.

“I can definitely see projects down the line as a result of conversations I had with those folks,” she said. “And developing collaborations now is very important to me.”

As described by Voytek and other NExSS leaders, another major focus of the group has been to encourage NASA headquarters to embrace some of the interdisciplinary approach they practice and are convinced is necessary.

This is part of a much longer effort by Voytek and other to include the search for life beyond Earth in the missions large and small that NASA develops. There was certainly resistance at times, but the agency has, in the past decade, made that search an increasingly central NASA goal.

As described by NExSS leader (or “Jedi”) Dawn Gelino, deputy director of the agency’s Exoplanet Science Institute, NASA headquarters has responded in other ways as well, and in recent months made two of its major research grant programs interdivisional.

That means scientists from quite different but nonetheless related disciplines can — for the first time — together propose projects for funding by those NASA programs. Thomas Zurbuchen, NASA’s associate administrator of the Science Mission Directorate, has been forceful in his support for this kind of approach.

“As a result of NExSS, we are definitely making a difference at headquarters in terms of the structure of teams responding to calls for proposals,” Gelino said.

A NExSS interdisciplinary approach is not for everyone, and some question its value. Many researchers would prefer to spend their time at the telescope, in the lab, with their modeling computers, writing papers — with laser focus on their areas of expertise. NExSS leaders regularly make the point that those decisions are understood and perfectly fine.

But especially in inherently interdisciplinary fields such as exoplanets and astrobiology, the pool of scientists willing to pitch in to advance the community appears to be large and has proven go be quite useful.

(Since I am writing about NExSS, I want to be clear in saying that the program helps support Many Worlds. A second column about NExSS brain-storming about the future of exoplanet and habitability studies will be coming soon.)

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About Many Worlds
There are many worlds out there waiting to fire your imagination.

Marc Kaufman is an experienced journalist, having spent three decades at The Washington Post and The Philadelphia Inquirer, and is the author of two books on searching for life and planetary habitability. While the “Many Worlds” column is supported by the Lunar Planetary Institute/USRA and informed by NASA’s NExSS initiative, any opinions expressed are the author’s alone.

This site is for everyone interested in the burgeoning field of exoplanet detection and research, from the general public to scientists in the field. It will present columns, news stories and in-depth features, as well as the work of guest writers.

About NExSS

The Nexus for Exoplanet System Science (NExSS) is a NASA research coordination network dedicated to the study of planetary habitability. The goals of NExSS are to investigate the diversity of exoplanets and to learn how their history, geology, and climate interact to create the conditions for life. NExSS investigators also strive to put planets into an architectural context — as solar systems built over the eons through dynamical processes and sculpted by stars. Based on our understanding of our own solar system and habitable planet Earth, researchers in the network aim to identify where habitable niches are most likely to occur, which planets are most likely to be habitable. Leveraging current NASA investments in research and missions, NExSS will accelerate the discovery and characterization of other potentially life-bearing worlds in the galaxy, using a systems science approach.
The National Aeronautics and Space Administration (NASA) is the agency of the United States government that is responsible for the nation’s civilian space program and for aeronautics and aerospace research.

President Dwight D. Eisenhower established the National Aeronautics and Space Administration (NASA) in 1958 with a distinctly civilian (rather than military) orientation encouraging peaceful applications in space science. The National Aeronautics and Space Act was passed on July 29, 1958, disestablishing NASA’s predecessor, the National Advisory Committee for Aeronautics (NACA). The new agency became operational on October 1, 1958.

Since that time, most U.S. space exploration efforts have been led by NASA, including the Apollo moon-landing missions, the Skylab space station, and later the Space Shuttle. Currently, NASA is supporting the International Space Station and is overseeing the development of the Orion Multi-Purpose Crew Vehicle and Commercial Crew vehicles. The agency is also responsible for the Launch Services Program (LSP) which provides oversight of launch operations and countdown management for unmanned NASA launches. Most recently, NASA announced a new Space Launch System that it said would take the agency’s astronauts farther into space than ever before and lay the cornerstone for future human space exploration efforts by the U.S.

NASA science is focused on better understanding Earth through the Earth Observing System, advancing heliophysics through the efforts of the Science Mission Directorate’s Heliophysics Research Program, exploring bodies throughout the Solar System with advanced robotic missions such as New Horizons, and researching astrophysics topics, such as the Big Bang, through the Great Observatories [Hubble, Chandra, Spitzer, and associated programs. NASA shares data with various national and international organizations such as from the [JAXA]Greenhouse Gases Observing Satellite.

From Carnegie Institution for Science: “When it comes to planetary habitability, it’s what’s inside that counts”

From Carnegie Institution for Science

May 01, 2019

Which of Earth’s features were essential for the origin and sustenance of life? And how do scientists identify those features on other worlds?

A team of Carnegie investigators with array of expertise ranging from geochemistry to planetary science to astronomy published this week in Science an essay urging the research community to recognize the vital importance of a planet’s interior dynamics in creating an environment that’s hospitable for life.

With our existing capabilities, observing an exoplanet’s atmospheric composition will be the first way to search for signatures of life elsewhere. However, Carnegie’s Anat Shahar, Peter Driscoll, Alycia Weinberger, and George Cody argue that a true picture of planetary habitability must consider how a planet’s atmosphere is linked to and shaped by what’s happening in its interior.

Reprinted with permission from Shahar et. al., Science Volume 364:3(2019).

For example, on Earth, plate tectonics are crucial for maintaining a surface climate where life can thrive. What’s more, without the cycling of material between its surface and interior, the convection that drives the Earth’s magnetic field would not be possible and without a magnetic field, we would be bombarded by cosmic radiation.

“We need a better understanding of how a planet’s composition and interior influence its habitability, starting with Earth,” Shahar said. “This can be used to guide the search for exoplanets and star systems where life could thrive, signatures of which could be detected by telescopes.”

It all starts with the formation process. Planets are born from the rotating ring of dust and gas that surrounds a young star. The elemental building blocks from which rocky planets form—silicon, magnesium, oxygen, carbon, iron, and hydrogen—are universal. But their abundances and the heating and cooling they experience in their youth will affect their interior chemistry and, in turn, things like ocean volume and atmospheric composition.

“One of the big questions we need to ask is whether the geologic and dynamic features that make our home planet habitable can be produced on planets with different compositions,” Driscoll explained.

The Carnegie colleagues assert that the search for extraterrestrial life must be guided by an interdisciplinary approach that combines astronomical observations, laboratory experiments of planetary interior conditions, and mathematical modeling and simulations.

Artist’s impression of the surface of the planet Barnard’s Star b courtesy of ESO/M. Kornmesser.

“Carnegie scientists are long-established world leaders in the fields of geochemistry, geophysics, planetary science, astrobiology, and astronomy,” said Weinberger. “So, our institution is perfectly placed to tackle this cross-disciplinary challenge.”

In the next decade as a new generation of telescopes come online, scientists will begin to search in earnest for biosignatures in the atmospheres of rocky exoplanets. But the colleagues say that these observations must be put in the context of a larger understanding of how a planet’s total makeup and interior geochemistry determines the evolution of a stable and temperate surface where life could perhaps arise and thrive.

“The heart of habitability is in planetary interiors,” concluded Cody.

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Carnegie Institution for Science

Andrew Carnegie established a unique organization dedicated to scientific discovery “to encourage, in the broadest and most liberal manner, investigation, research, and discovery and the application of knowledge to the improvement of mankind…” The philosophy was and is to devote the institution’s resources to “exceptional” individuals so that they can explore the most intriguing scientific questions in an atmosphere of complete freedom. Carnegie and his trustees realized that flexibility and freedom were essential to the institution’s success and that tradition is the foundation of the institution today as it supports research in the Earth, space, and life sciences.

6.5 meter Magellan Telescopes located at Carnegie’s Las Campanas Observatory, Chile

Carnegie Las Campanas 2.5 meter Irénée Dupont telescope, Atacama Desert, over 2,500 m (8,200 ft) high approximately 100 kilometres (62 mi) northeast of the city of La Serena,Chile

Carnegie Institution Swope telescope at Las Campanas, Chile, 100 kilometres (62 mi) northeast of the city of La Serena. near the north end of a 7 km (4.3 mi) long mountain ridge. Cerro Las Campanas, near the southern end and over 2,500 m (8,200 ft) high, at Las Campanas, Chile

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From Astrobiology Magazine: “German Aerospace Center: Institute of Planetary Research”

From Astrobiology Magazine

Jan 28, 2019
Starre Vartan

The BIOMEX experiment, performed by DLR, being attached by astronauts to the exterior of the International Space Station. Image credit: ESA.

Each of NASA’s international astrobiology partners take a different tack in looking for the answer to the question of whether there is life elsewhere in the Universe.

A creative, multi-pronged investigation is necessary with such a complicated problem – the answer will draw on a collaborative approach among biologists, geologists, chemists and many others.

In the case of the German Aerospace Center (DLR)’s Institute of Planetary Research, there are two areas on which they focus their attention.

DLR specializes in developing technology for space missions, including photometric technology, radiometers, laser altimeters, thermal probes and spectrometers, and contributes to NASA projects including Cassini, InSight and Dawn, plus European Space Agency (ESA) missions such as CoRoT, Rosetta and ExoMars and the forthcoming JUICE (JUpiter ICy moons Explorer) spacecraft. In particular, cameras are a speciality.

NASA/ESA/ASI Cassini-Huygens Spacecraft

NASA/Mars InSight Lander

NASA Dawn Spacescraft

ESA/CoRoT

ESA/Rosetta spacecraft

ESA/ExoMars

ESA/Juice spacecraft

“For example, we built a high-resolution stereo camera for Mars Express, which is the oldest camera on a European Space Agency mission still in operation,” says Professor Heike Rauer, the new Director of the DLR Institute of Planetary Research. “It’s been running for 15 years, and takes 3D images.”

Those high-resolution, color images have revealed details about Mars’ geologic and climate history, including evidence of ancient water flows that have led to evidence-based discussions of human habitability and settlement on the red planet.

In addition, DLR has performed astrobiological experiments, for example BIOMEX (BIOlogy and Mars Experiment) [above] on board the International Space Station, which tests the extent to which extremophiles can survive in particular space environments. Furthermore, Rauer is head of a consortium developing an instrument for the planet-finding PLATO mission that will detect and characterize Earth-like planets in the habitable zone of Sun-like stars.

ESA/PLATO

This ties in with their second focus, which is to understand the evolution of planets, both in ourSolar System and around other stars.By understanding the planetary processes that make life possible, the search for life elsewhere can be concentrated on the places where it’s most likely to have evolved.

Helmholtz Alliance

This aspect of DLR’s work began with the Helmholtz Alliance‘Planetary Evolution and Life’ project. The Helmholtz Alliance is a science-focused program of the German government designed to solve “the grand challenges of science, society and industry.” Helmholtz gives out five-year grants to scientists who work in German institutions and elsewhere to come together on collaborative projects that especially aim to involve young people and promote equal opportunity.

DLR’s planetary research work was funded in 2008 by Helmholtz and continued through 2015, having received an extension on the work in order to use up all the funds.

In the framework of the Helmholtz Alliance, DLR became an affiliated partner of the NASA Astrobiology Institute (NAI) in early 2013. The Helmholtz program was only meant to be a one-time ‘jump-start’ for a research area, which is exactly what was accomplished with the $5 million euro per annum fund that made Germany one of the leading nations in planetary research. The planetary evolution work at DLR is now a regular research program with a long-term funding perspective, says the Alliance’s former director, Professor Tilman Spohn. While funding isn’t quite as robust as it once was under Helmholtz, it still stands as an independent program at the DLR.

During the six years that planetary evolution research was a Helmholtz program, “We did some exoplanetary research, but we had a strong focus on Mars,” says Spohn. “We made major contributions using the data from Mars Express to look into the various [potentially] habitable provinces on Mars to find where life could have originated and could still be present.

ESA Mars Express Orbiter

It was good to start something new and interesting and then make it sustainable [under the aegis of DLR].”

Where to look for life

The big question that the planetary research program is currently attempting to answer is the same as before: how can we figure out which of the many planets outside our Solar System might harbor life? Scientists need to set defined parameters in order to make smart guesses about where to look. So they look for what life might leave behind, or signs that might reveal indirect evidence for life. Life might exist now, but may not be obvious, so looking for coincident or non-obvious signs of life is important. Elsewhere in the Solar System, life is more likely to have existed in the past than in the present, so what might it have left behind?

“We are looking for a better understanding of habitability and of biosignatures,” says Rauer. “In one case –our Solar System –we can go and look, but with extrasolar planets we cannot go there, which means the only way we can detect life is by studying the atmospheres of exoplanets.”

That’s why DLR is looking closely at “the link between interiors, surface and atmosphere,” of planets, says Rauer. Understanding how each of those planetary regions affects the others enables scientists to see what might be produced by normal geologic or chemical processes, for example – and what might be anomalous.

DLR is looking at some big questions that could apply to a wide variety of types of life, from single-celled to multicellular. “How does life leave imprints on the atmosphere? That’s important for places where we can’t send rovers,” says Rauer. She says that knowing what signs to look for could enable future researchers to scan for life simply by looking at the atmosphere of a planet. Of course, it’s also important for astrobiologists to study how life has “interactions with the surface and could leave its impact there.”

Other related questions include how life might affect the evolution of an entire planet over time. “This is a novel look at planetary geophysics – how do tectonics and interior structures influence the development of lifeforms?” asks Rauer. Since Earth has developed in tandem with life, and life has been affected by the geophysics of the Earth, we know that both of these things have happened at least once, here. So, looking for those signs and asking those questions elsewhere makes sense.

To that end, DLR works on modeling planet formation and tectonics, the inner structures of planets, how magnetic fields originate, and how meteor impacts affect all of the above. They also engage, along with their partners, in laboratory investigations of extremophiles in conditions similar to Mars or space, and how water behaves in different environments. And, of course, they are figuring out how to detect organisms on the surface of a planet.

Research areas

All of these questions fit within six specific areas that DLR’s Planetary Evolution and Life program tackles, often interdependently:

Biosphere–Atmosphere–Surface Interaction and Development
Planet–Interior Atmosphere Interaction
Magnetic Field and Planetary Evolution
Impacts and Planetary Evolution; Geological Context of Life
Physics and Biology of Interface Water
Strategies and Realizations of Missions for Exploration of planetary habitability.

The Planetary Evolution and Life program started, as many great projects do, with the feeling that there was an understudied area that needed attention. Spohn says that he has long looked at the evolution of planets, including Earth, Mars, Venus and others. “But we never looked at the potential effect of life on these planets. I thought to myself that maybe we should include the interaction of life with planetary processes in our modeling. Nobody in the previous astrobiology community had really looked into a combination of geophysical tools and modeling together with the effects of life.”

Under the Helmholtz Alliance, the Planetary Evolution program worked with – and plans to continue working with, as part of DLR – international partners across Europe and beyond, including ESA, NASA Ames, NASA’s Jet Propulsion Laboratory, the Johns Hopkins University Applied Physics Laboratory, the Japan Aerospace Exploration Agency (JAXA), the French Centre national de la recherche scientifique (CNRS) and Centre national d’études spatiales (CNES), and many other institutions and universities around the world.

An important part of DLR’s work under Helmholtz was supporting and involving grad students and early-career scientists in both the questions and the work the institute undertook. “Much of the work has been done by students, young grad students and post-docs,” says Spohn. “We let students in on many aspects of the work, and they also looked into missions – how they are devised and managed, and put into space, so they see the whole process.”

This aspect of the program is likely to continue, as young scientists are drawn to the still-unanswered question: “Are we alone in the Universe?”

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From UC Riverside: “Are We Alone?”

From UC Riverside

May 24, 2018
Sarah Nightingale

Illustration by The Brave Union

Forty years ago, the Voyager 2 spacecraft launched from Florida’s Cape Canaveral. Over the next decade, it swept across the solar system, sending back images of Jupiter’s volcanoes, Saturn’s rings, and for the first time, the icy atmospheres of Uranus and Neptune.

NASA/Voyager 2

UCR’s Tim Lyons, left, and Stephen Kane are some of the only researchers in the world using Earth’s history as a guide to finding life in outer space. (Photo by Kurt Miller)

The mission was more than enough to encourage Stephen Kane, a teenager growing up in Australia, to study planetary science in college. By the time he’d graduated, scientists had detected the first planet outside our solar system, known as an exoplanet, inspiring him to join the hunt and look for more.

Over the past two decades, Kane, now an associate professor of planetary astrophysics at UC Riverside, has discovered hundreds of alien planets. At first, he focused on identifying giant Jupiter-like planets, which he describes as “low-hanging fruit” due to their large sizes. But in 2011, the Kepler Space Telescope identified the first rocky planet — Kepler 10b. Unlike gas giants such as Jupiter, rocky planets could potentially harbor life.

NASA/Kepler Telescope

With the discovery of more Earth-sized planets on the horizon, Kane realized that astrophysicists would struggle to understand the data they were receiving about terrestrial planets and their atmospheres.

“During the course of the ongoing Kepler mission, I sought out planetary and Earth scientists because they’ve spent hundreds of years studying the solar system and how the Earth’s atmosphere has been shaped by biological and geophysical processes, so they have a lot to bring to the table,” Kane said.

In 2017, Kane formalized that collaboration by joining an interdisciplinary research group led by Tim Lyons, a distinguished professor of biogeochemistry in the Department of Earth Sciences and director of UCR’s Alternative Earths Astrobiology Center. Backed by roughly $7.5 million from NASA, the center, one of only a handful like it in the world, brings together geochemists, biologists, planetary scientists, and astrophysicists from UCR and partner institutions to search for life on distant worlds using a template defined by the only known planet with life: Earth.

Astrobiology researchers study areas on Earth that hold evidence of ancient life, such as these stromatolites at the Hamelin Pool Marine Nature Reserve in Shark Bay, Australia. The rocky, dome-shaped structures formed in shallow water through the trapping of sedimentary grains by communities of microorganisms. (Photo by Mark Boyle)

Fingerprinting Life

Since its formation more than 4.5 billion years ago, Earth has undergone immense periods of geological and biological change.

When the first life appeared — in the form of simple microbes — the sun was fainter, there were no continents, and there was no oxygen in the atmosphere. A new kind of life emerged around 2.7 billion years ago: photosynthetic bacteria that use the sun’s energy to convert carbon dioxide and water into food and oxygen gas. Multicellular life evolved from those bacteria, followed by more familiar lifeforms: fish about 530 million years ago, land plants 470 million years ago, and mammals 200 million years ago.

“There are periods in the Earth’s past that are as different from one another as Earth is from an exoplanet,” Lyons said. “That is the concept of alternative Earths. You can slice the Earth’s history into chapters, pages, and even paragraphs, and there has been life evolving, thriving, surviving, and dying with each step. If we know what kind of atmospheres were present during the early stages of life on Earth, and their relationships to the evolving continents and oceans, we can look for similar signposts in our search for life on exoplanets.”

While it might seem impossible to characterize ancient oceans and atmospheres, scientists can glean hints by studying rocks formed billions of years ago.

“The chemical compositions of rocks are determined by the chemistry of the oceans and their life, and many of the gases in the atmosphere, through exchange with the oceans, are controlled by the same processes,” Lyons said. “These atmospheric fingerprints of life in the underlying oceans, or biosignatures, can be used as markers of life on other planets light years away.”

The search for alien biosignatures typically centers on the gases produced by living creatures on Earth because they’re the only examples scientists have to work with. But Earth’s many chapters of inhabitation reveal the great number of possible gas combinations. Oxygen gas, ozone, and methane in a planet’s biosignature could all indicate the presence of life — and seeing them together could present an even stronger argument.

The center’s search for life is different from the hunt for intelligent life. While those researchers probe for signs of alien civilizations, such as radio waves or powerful lasers, Lyons’ team is essentially looking for the byproducts of simple lifeforms.

“As we’re exploring exoplanets, what we’re really trying to do is characterize their atmospheres,” he said. “If we see certain profiles of gases, then we may be detecting microbial waste products that are accumulating in the atmosphere.”

The UCR team must also account for processes that produce the same gases without contributions from life, a phenomenon researchers call false positives. For example, a planetary atmosphere with abundant oxygen would be a promising biosignature, but that evidence could be misleading without fully addressing where it came from. Similarly, methane is a key biosignature, but there are many nonbiological ways to produce this gas on Earth. These distinctions require careful considerations of many factors, including seasonal patterns, tectonic activity, the type of planet and its star, among other data.

False negatives are another concern, Lyons said. In previous research on ancient organic-rich rocks collected in Western Australia and South Africa, his group showed that about two billion years passed between the moment organisms first started producing oxygen on Earth and when it accumulated at levels high enough to be detectable in the atmosphere. In that scenario, a classic biosignature, oxygen, could be missed.

“It’s also entirely possible that on some planets oxygen is produced through photosynthesis in pockets in the ocean and you’d never see it in the atmosphere,” Lyons said. “We have to be very clever to consider the many possibilities for biosignatures, and Earth’s past gives us many to choose from.”

Illustration by The Brave Union

‘Following the Water’

With several hundred terrestrial planets confirmed and many more awaiting discovery, the search for life-bearing worlds is an almost overwhelming task.

Astronomers are narrowing down their search by focusing on habitable zones — the orbital region around stars where it’s neither too hot nor too cold for liquid water to exist on the surface.

“We know that liquid water is essential for life as we know it, and so we’re beginning our search by looking for planets that are capable of having similar environments to Earth. We call this approach ‘following the water,’” Kane said.

While the habitable zone serves as a target selection tool, Kane said a planet nestled in this region won’t necessarily show signs of life — or even liquid water. Venus, for example, occupies the inner edge of the Sun’s habitable zone, but its scorching surface temperature has boiled away any liquid water that once existed.

“We are extremely fortunate to have Venus in our solar system because it reminds us that a planet can be exactly the same size as Earth and still have things go catastrophically wrong,” Kane said.

Equally important, being in the habitable zone doesn’t mean a planet will boast other factors that make Earth ideal for life. In addition to liquid water, the perfect candidate would have an insulating atmosphere and a protective magnetic field. It would also offer the right chemical ingredients for life and ways of recycling those elements over and over when continents collide, mountains lift up and wear down, and nutrients are swept back to the seas by rivers.

“People question why we focus so intently on Earth, but the answer is obvious. We only know what we know about life because of what the Earth has given us,” said Lyons, who has spent decades reconstructing the conditions during which life evolved.

“If I asked you to design a planet with the perfect conditions for life, you would design something just like Earth because it has all of these essential features,” he added. “We are studying how these building blocks have been assembled in different ways during Earth’s history and asking which of them are essential for life, which can be taken away. From that vantage point, we ask how they could be assembled in very different ways on other planets and still sustain life.”

Kane said a distant planetary system called TRAPPIST-1, which NASA scientists discovered in 2017, could provide clues about the ingredients that are necessary for life.

A size comparison of the planets of the TRAPPIST-1 system, lined up in order of increasing distance from their host star. The planetary surfaces are portrayed with an artist’s impression of their potential surface features, including water, ice, and atmospheres. NASA

The TRAPPIST-1 star, an ultracool dwarf, is orbited by seven Earth-size planets (NASA).

ESO Belgian robotic Trappist National Telescope at Cerro La Silla, Chile

ESO Belgian robotic Trappist National Telescope at Cerro La Silla, Chile

Although miniature compared to our own solar system — TRAPPIST-1 would easily fit inside Mercury’s orbit around the sun — it boasts seven planets, three of which are in the habitable zone. However, the planets don’t have moons, and they may not even have atmospheres.

“We are finding that compact planetary systems orbiting faint stars are much more common than larger systems, so it’s important that we study them and find out if they could have habitable environments,” Kane said.

An artist’s illustration of the possible surface of TRAPPIST-1f, one of the planets in the TRAPPIST-1 system.

Remote Observations

At about 40 light-years (235 trillion miles) from Earth, the TRAPPIST-1 system is relatively close, but we’re never going to go there.

“The fascinating thing about astronomy as a science is that it’s all based on remote observations,” Kane said. “We are trying to squeeze every piece of information we can out of photons that we are receiving from a very distant object.”

While scientists have studied the atmospheres of several dozen exoplanets, most are too distant to probe with current instruments. That situation is changing. In April, NASA launched its Transiting Exoplanet Survey Satellite, known as TESS, which will seek Earth-sized planets around more than 500,000 nearby stars.

NASA/MIT TESS

In May 2020, NASA plans to launch the James Webb Space Telescope, which will perform atmospheric studies of the rocky worlds discovered by TESS.

NASA/ESA/CSA Webb Telescope annotated

Like Kepler, TESS detects exoplanets using the transit method, which measures the minute dimming of a star as an orbiting planet passes between it and the Earth.

Planet transit. NASA/Ames

Because light also passes through the atmosphere of planets, scientists will use the Webb telescope to identify the blanket of gases surrounding them through a technique called spectroscopy.

Kane and Lyons are working with NASA to design missions that will directly image exoplanets in ways that will ensure that interdisciplinary teams such as theirs can properly interpret a wide variety of planetary processes.

“As we design future missions, we must make sure they are equipped with the right instruments to detect biosignatures and geological processes, such as active volcanoes,” Kane said.

UCR’s astrobiology team is one of only a few groups in the world studying ancient Earth to create a catalog of biosignatures that will inform mission design in NASA’s search for life on distant worlds. With quintillions — think the number of gallons of water in all of our oceans — of potentially habitable planets in the universe, Lyons said he is optimistic that we’ll find signs of life in the future.

“Just like the Voyager missions were important because of what they taught us about our solar system — from the discovery of Jupiter’s rings to the first close-up glimpses of Uranus and Neptune — the TESS and James Webb missions, and more importantly the next generation of telescopes planned for the coming decades, are very likely to change our understanding of distant space,” Lyons said. And perhaps nestled in those discoveries will be an answer to the most fundamental of all questions, ‘are we alone?’

Alternative Earths Astrobiology Center

Founded in 2015

One of 12 research teams funded by the NASA Astrobiology Institute, and one of only two using Earth’s history to guide exoplanet exploration

Awarded $7.5 million over five years to cultivate a “search engine” for life on planets orbiting distant stars using Earth’s evolution over billions of years as a template

Builds on existing UCR strengths in biogeochemistry, Earth history, and astrophysics

Unites 66 researchers and staff at 11 institutions around the world, including primary partners led by former UCR graduate students now on the faculty at Yale and Georgia Tech

A NASA illustration of TESS monitoring stars outside our solar system.

Through the Looking Glass

In April, the Transiting Exoplanet Survey Satellite (TESS) Mission launched with the goal of discovering new Earths and super-Earths around nearby stars. As a guest investigator on the TESS Mission, Stephen Kane will use University of California telescopes, including those at the Lick Observatory in Mt. Hamilton to help determine whether candidate exoplanets identified by TESS are actually planets.

UCSC Lick Observatory, Mt Hamilton, in San Jose, California, Altitude 1,283 m (4,209 ft)

UCSC Lick Automated Planet Finder telescope, Mount Hamilton, CA, USA

The UCO Lick C. Donald Shane telescope is a 120-inch (3.0-meter) reflecting telescope located at the Lick Observatory, Mt Hamilton, in San Jose, California, Altitude 1,283 m (4,209 ft)

UC Santa Cruz Shelley Wright at the 1-meter Nickel Telescope NIROSETI

NIROSETI team from left to right Rem Stone UCO Lick Observatory Dan Werthimer UC Berkeley Jérôme Maire U Toronto, Shelley Wright UCSD Patrick Dorval U Toronto Richard Treffers Richard Treffers Starman Systems. (Image by Laurie Hatch)

By studying the planet mass data obtained from the ground-based telescopes and planet diameter readings from spacecraft observations, Kane will also help determine the overall composition of the newly identified planets.

See the full article here .

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The University of California, Riverside is one of 10 universities within the prestigious University of California system, and the only UC located in Inland Southern California.

Widely recognized as one of the most ethnically diverse research universities in the nation, UCR’s current enrollment is more than 21,000 students, with a goal of 25,000 students by 2020. The campus is in the midst of a tremendous growth spurt with new and remodeled facilities coming on-line on a regular basis.

We are located approximately 50 miles east of downtown Los Angeles. UCR is also within easy driving distance of dozens of major cultural and recreational sites, as well as desert, mountain and coastal destinations.

From JHU HUB: “Alien imposters: Planets with oxygen don’t necessarily have life, study finds”

From JHU HUB

12.17.18
Chanapa Tantibanchachai

Chao He shows off the lab’s PHAZER setup. Image credit: Chanapa Tantibanchachai

In their search for life in solar systems near and far, researchers have often accepted the presence of oxygen in a planet’s atmosphere as the surest sign that life may be present there. A new Johns Hopkins study, however, recommends a reconsideration of that rule of thumb.

Simulating in the lab the atmospheres of planets beyond the solar system, researchers successfully created both organic compounds and oxygen, absent of life.

The findings, published Dec. 11 by the journal ACS Earth and Space Chemistry, serve as a cautionary tale for researchers who suggest the presence of oxygen and organics on distant worlds is evidence of life there.

A CO2-rich planetary atmosphere exposed to a plasma discharge in Sarah Hörst’s lab. Image credit: Chao He

“Our experiments produced oxygen and organic molecules that could serve as the building blocks of life in the lab, proving that the presence of both doesn’t definitively indicate life,” says Chao He, assistant research scientist in the Johns Hopkins University Department of Earth and Planetary Sciences and the study’s first author. “Researchers need to more carefully consider how these molecules are produced.”

Oxygen makes up 20 percent of Earth’s atmosphere and is considered one of the most robust biosignature gases in Earth’s atmosphere. In the search for life beyond Earth’s solar system, however, little is known about how different energy sources initiate chemical reactions and how those reactions can create biosignatures like oxygen. While other researchers have run photochemical models on computers to predict what exoplanet atmospheres might be able to create, no such simulations to his knowledge have before now been conducted in the lab.

The research team performed the simulation experiments in a specially designed Planetary HAZE (PHAZER) chamber in the lab of Sarah Hörst, assistant professor of Earth and planetary sciences and the paper’s co-author. The researchers tested nine different gas mixtures, consistent with predictions for super-Earth and mini-Neptune type exoplanet atmospheres; such exoplanets are the most abundant type of planet in our Milky Way galaxy. Each mixture had a specific composition of gases such as carbon dioxide, water, ammonia, and methane, and each was heated at temperatures ranging from about 80 to 700 degrees Fahrenheit.

He and the team allowed each gas mixture to flow into the PHAZER setup and then exposed the mixture to one of two types of energy, meant to mimic energy that triggers chemical reactions in planetary atmospheres: plasma from an alternating current glow discharge or light from an ultraviolet lamp. Plasma, an energy source stronger than UV light, can simulate electrical activities like lightning and/or energetic particles, and UV light is the main driver of chemical reactions in planetary atmospheres such as those on Earth, Saturn, and Pluto.

After running the experiments continuously for three days, corresponding to the amount of time gas would be exposed to energy sources in space, the researchers measured and identified resulting gasses with a mass spectrometer, an instrument that sorts chemical substances by their mass to charge ratio.

The research team found multiple scenarios that produced both oxygen and organic molecules that could build sugars and amino acids—raw materials for which life could begin—such as formaldehyde and hydrogen cyanide.

“People used to suggest that oxygen and organics being present together indicates life, but we produced them abiotically in multiple simulations,” He says. “This suggests that even the co-presence of commonly accepted biosignatures could be a false positive for life.”

See the full article here .

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About the Hub
We’ve been doing some thinking — quite a bit, actually — about all the things that go on at Johns Hopkins. Discovering the glue that holds the universe together, for example. Or unraveling the mysteries of Alzheimer’s disease. Or studying butterflies in flight to fine-tune the construction of aerial surveillance robots. Heady stuff, and a lot of it.

In fact, Johns Hopkins does so much, in so many places, that it’s hard to wrap your brain around it all. It’s too big, too disparate, too far-flung.

We created the Hub to be the news center for all this diverse, decentralized activity, a place where you can see what’s new, what’s important, what Johns Hopkins is up to that’s worth sharing. It’s where smart people (like you) can learn about all the smart stuff going on here.

At the Hub, you might read about cutting-edge cancer research or deep-trench diving vehicles or bionic arms. About the psychology of hoarders or the delicate work of restoring ancient manuscripts or the mad motor-skills brilliance of a guy who can solve a Rubik’s Cube in under eight seconds.

There’s no telling what you’ll find here because there’s no way of knowing what Johns Hopkins will do next. But when it happens, this is where you’ll find it.

The Johns Hopkins University opened in 1876, with the inauguration of its first president, Daniel Coit Gilman. “What are we aiming at?” Gilman asked in his installation address. “The encouragement of research … and the advancement of individual scholars, who by their excellence will advance the sciences they pursue, and the society where they dwell.”

The mission laid out by Gilman remains the university’s mission today, summed up in a simple but powerful restatement of Gilman’s own words: “Knowledge for the world.”

What Gilman created was a research university, dedicated to advancing both students’ knowledge and the state of human knowledge through research and scholarship. Gilman believed that teaching and research are interdependent, that success in one depends on success in the other. A modern university, he believed, must do both well. The realization of Gilman’s philosophy at Johns Hopkins, and at other institutions that later attracted Johns Hopkins-trained scholars, revolutionized higher education in America, leading to the research university system as it exists today.

From COSMOS Magazine: “The tech we’re going to need to detect ET”

From COSMOS Magazine

09 November 2018
Lauren Fuge

Searching for biosignatures rather than examples of life itself is considered a prime strategy in the hunt for ET. smartboy10/Getty Images

Move over Mars rovers, new technologies to detect alien life are on the horizon.

A group of scientists from around the world, led by astrochemistry expert Chaitanya Giri from the Tokyo Institute of Technology in Japan, have put their heads together to plan the next 20 years’ worth of life-detection technologies. The study is currently awaiting peer review, but is freely available on the pre-print site, ArXiv.

For decades, astrobiologists have scoured the skies and the sands of other planets for hints of extraterrestrial life. Not only are these researchers trying to find ET, but they’re also aiming to learn about the origin and evolution of life on Earth, the chemical composition of organic extraterrestrial objects, what makes a planet or satellite habitable, and more.

But the answers to such questions are preceded by long years of planning, development, problem-solving and strategising.

Late in 2017, 20 scientists from Japan, India, France, Germany and the USA – each with a special area of expertise – came together at a workshop run by the Earth-Life Science Institute (ELSI) at Giri’s Tokyo campus. There, they discussed the current progress and enticing possibilities of life-detection technologies.

In particular, the boffins debated which ones should be a priority for research and development for missions within the local solar system – in other words, which instruments will be most feasible to out onto a space probe and send off to Mars or Enceladus during the next couple of decades.

Of course, the planets and moons in the solar system are an extremely limited sample of the number of potentially habitable worlds in the universe, but understanding our own backyard will be key in interpreting data from far-flung exoplanets.

So, according to these astrobiology experts, what’s the future plan for alien detection?

The first step of any space mission is to study the planet or satellite from afar to determine whether it is habitable. Luckily, an array of next-generation telescopes is currently being built, from the ultra-sensitive James Webb Space Telescope, slated for launch in 2021, to the gargantuan Extremely Large Telescope in Chile, which will turn its 39-metre eye to the sky in 2024. The authors point out that observatories such as these will vastly expand our theoretical knowledge of planet habitability.

NASA/ESA/CSA Webb Telescope annotated

ESO/E-ELT,to be on top of Cerro Armazones in the Atacama Desert of northern Chile. located at the summit of the mountain at an altitude of 3,060 metres (10,040 ft).

Just because a world is deemed habitable doesn’t mean life will be found all over it, though. It may exist only in limited geographical niches. To reach these inaccessible sites, the paper argues that we will require “agile robotic probes that are robust, able to seamlessly communicate with orbiters and deep space communications networks, be operationally semi-autonomous, have high-performance energy supplies, and are sterilisable to avoid forward contamination”.

But according to Elizabeth Tasker, associate professor at the Japan Aerospace Exploration Agency (JAXA), who was not involved in the study, getting there is only half the struggle.

“In fact, it’s the most tractable half because we can picture the problems we will face,” she says.

The second, more pressing issue is how to recognise life unlike anything we know on Earth.

As Tasker explains: “We only have Earth life to compare to and this is the result of huge evolutionary history on a planet whose complex past is unlikely to be replicated closely. That’s a lot of baggage to separate out.”

According to the paper, the way forward is to equip missions with a suite of life-detection instruments that don’t look for life as we know it, but are instead able to identify the kinds of features that make organisms function.

The authors outline a huge variety of exciting technologies that could be used for this purpose, including spectroscopy techniques (to analyse potential biological materials), quantum tunnelling [Nature Nanotechnology
] (to find DNA, RNA, peptides, and other small molecules), and fluorescence microscopy [ https://www.hou.usra.edu/meetings/lpsc2014/pdf/2744.pdf ](to identify the presence of cell membranes).

They also nominate different forms of gas chromatography (to spot amino acids and sugars formed by living organisms, plus checking to see if molecules are “homochiral” [Space Science Reviews] (a suspected biosignature) using microfluidic devices and microscopes.

High-resolution, miniaturised mass spectrometers would also be helpful, characterising biopolymers, which are created by living organisms, and measuring the elemental composition of objects to aid isotopic dating.

Giri and colleagues also stress that exciting developments in machine learning, artificial intelligence, and pattern recognition will be useful in determining whether chemical samples are biological in origin.

Interestingly, researchers are also developing technologies that may allow the detection of life in more unconventional places. On Earth, for example, cryotubes were recently used [International Journal of Systematic and Evolutionary Microbiology] to discover several new species of bacteria in the upper atmosphere.

The scientists also discuss how certain technologies – such as high-powered synchrotron radiation and magnetic field facilities – are not yet compact enough to fly to other planets, and so samples must continue to be brought back for analysis.

Several sample-and-return missions are currently underway, including JAXA’s Martian Moons exploration mission to Phobos, Hayabusa-2 to asteroid Ryugu, and NASA’s OSIRIS-rex to asteroid Bennu. What we learn from handling the organic-rich extraterrestrial materials brought back from these trips will be invaluable.

JAXA MMX spacecraft

JAXA/Hayabusa 2 Credit: JAXA/Akihiro Ikeshita

NASA OSIRIS-REx Spacecraft

What we learn from handling the organic-rich extraterrestrial materials brought back from these trips will be invaluable.

The predictions and recommendations put forward by Giri and colleagues are the first steps in getting these technologies discussed in panel reviews, included in decadal surveys, and eventually funded.

They complement several similar efforts, including a report prepared by US National Academies of Science, Engineering and Medicine (NASEM), calling for an expansion of the range of possible ET indicators, and a US-led exploration of how the next generation of radio telescopes will be utilised by SETI.

Perhaps most importantly, these papers all highlight the need for collaborative work between scientists across disciplines.

“A successful detection of life will need astrophysicists and geologists to examine possible environments on other planets, engineers and physicists to design the missions and instruments that can collect data, and chemists and biologists to determine how to classify life,” JAXA’s Tasker says.

“But maybe that is appropriate: finding out what life really is and where it can flourish is the story of everyone on Earth. It should take all of us to unravel.”

See the full article here .

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From Many Worlds: “False Positives, False Negatives; The World of Distant Biosignatures Attracts and Confounds”

NASA NExSS

Many Worlds

2018-01-29
Marc Kaufman

This artist’s illustration shows two Earth-sized planets, TRAPPIST-1b and TRAPPIST-1c, passing in front of their parent red dwarf star, which is much smaller and cooler than our sun. NASA’s Hubble Space Telescope looked for signs of atmospheres around these planets. (NASA/ESA/STScI/J. de Wit, MIT)

NASA/ESA Hubble Telescope

What observations, or groups of observations, would tell exoplanet scientists that life might be present on a particular distant planet?

The most often discussed biosignature is oxygen, the product of life on Earth. But while oxygen remains central to the search for biosignatures afar, there are some serious problems with relying on that molecule.

It can, for one, be produced without biology, although on Earth biology is the major source. Conditions on other planets, however, might be different, producing lots of oxygen without life.

And then there’s the troubling reality that for most of the time there has been life on Earth, there would not have been enough oxygen produced to register as a biosignature. So oxygen brings with it the danger of both a false positive and a false negative.

Wading through the long list of potential other biosignatures is rather like walking along a very wet path and having your boots regularly pulled off as they get captured by the mud. Many possibilities can be put forward, but all seem to contain absolutely confounding problems.

With this reality in mind, a group of several dozen very interdisciplinary scientists came together more than a year ago in an effort to catalogue the many possible biosignatures that have been put forward and then to describe the pros and the cons of each.

“We believe this kind of effort is essential and needs to be done now,” said Edward Schwieterman, an astronomy and astrobiology researcher at the University of California, Riverside. “Not because we have the technology now to identify these possible biosignatures light years away, but because space and ground telescopes of the future need to know what to look for and what kind of equipment they will need to make the potentially find it.

“It’s part of the very long road to learning whether or not we are alone in the universe.”

Artistic representations of some of the exoplanets detected so far with the greatest potential to support liquid surface water, based on their size and orbit. All of them are larger than Earth and their composition and habitability remains unclear. They are ranked here from closest to farthest from Earth. Mars, Jupiter, Neptune an Earth are shown for scale on the right. (Planetary Habitability Laboratory, managed by the University of Puerto Rico at Arecibo.)

The known and inferred population of exoplanets — even small rocky exoplanets — is now so vast that it’s tempting to assume that some support life and that some day we’ll find it. After all, those billions of planets are composed of same basic chemical elements as Earth and are subject to the same laws of physics.

That assumption of life widespread in the galaxies may well turn out to be on target. But assuming this result, and proving or calculating a high probability of finding extraterrestrial life, are light years apart.

The timing of this major community effort is hardly accidental. There is a National Academy of Sciences effort underway to review progress in the science of reading possible biosignatures from distant worlds, something that I wrote about recently.

The results from the NAS effort will in term flow into the official NAS decadal study that will follow and will recommend to Congress priorities for the next ten or twenty years. In addition, two NASA-ordered science and technology definition teams are currently working on architectures for two potential major NASA missions for the 2030s — HabEx (the Habitable Exoplanet Imaging Mission) and Luvoir (the Large Ultraviolet/Optical/Infrared Surveyor.)

The two mission proposals, which are competing with several others, would provide the best opportunity by far to determine whether life exists on other distant planets.

With these formal planning and prioritizing efforts as a backdrop, NASA’s Nexus for Exoplanet System Science (NExSS) called for a biosignatures workshop in the fall of 2016 and brought together scientists from many disciplines to wrestle with the subject. The effort led to the white paper submitted to NAS and will result in publication of as many as five much more detailed papers in the journal Astrobiology this spring. The overview paper with Schwieterman as first author, which has already been made available to the community for peer review, is expected to lead off the package.

So what did they find? First off, that Earth has to be their guide.

“Life on Earth, through its gaseous products and reflectance and scattering properties, has left its fingerprint on the spectrum of our planet,” the paper reads. “Aided by the universality of the laws of physics and chemistry, we turn to Earth’s biosphere, both in the present and through geologic time, for analog signatures that will aid in the search for life elsewhere.

Considering the insights gained from modern and ancient Earth, and the broader array of hypothetical exoplanet possibilities, we have compiled a state-of-the-art overview of our current understanding of potential exoplanet biosignatures including gaseous, surface, and temporal biosignatures.”

In other words, potential biosignatures in the atmosphere, on the ground, and that become apparent over time. We’ll start with the temporal:

These vegetation maps were generated from MODIS/Terra measurements of the Normalized Difference Vegetation Index (NDVI). Significant seasonal variations in the NDVI are apparent between northern hemisphere summer and winter. (Reto Stockli, NASA Earth Observatory Group, using data from the MODIS Land Science Team.)

NASA AQUA MODIS

NASA/Terra satellite

Vegetation is probably clearest example of how change-over-time can be a biosignature. As these maps show and we all know, different parts of the Earth have different seasonal colorations. Detecting exoplanetary change of this sort would be a potentially strong signal, though it could also have some non-biological explanations.

If there is any kind of atmospheric chemical corroboration, then the time signal would be a strong one. That corroboration could come in seasonal modulations of biologically important gases such as CO2 or O2. Changes in cloud cover and the periodic presence of volcanic gases can also be useful markers over time.

Plant pigments themselves which have been proposed as a surface biosignature. Observed in the near infrared portion of the electromagnetic spectrum, the pigment chlorophyll — the central player in the process of photosynthesis — shows a sharp dropoff in reflectance at a particular wavelength. This abrupt change is called the “red edge,” and is a measurement known to exist only which chlorophyll engaged in photosynthesis.

So the “red edge,” or parallel dropoffs in reflectance of other pigments on other planets, is another possible biosignature in the mix.

And then there is “glint,” reflections from exoplanets that come from light hitting water.

True-color image from a model (left) compared to a view of Earth from the Earth and Moon Viewer (http://www.fourmilab.ch/cgi-bin/Earth/). A glint spot in the Indian Ocean can be clearly seen in the model image.

Since biosignature science essentially requires the presence of H2O on a planet, the clear detection of an ocean is part of the process of assembling signatures of potential life. Just as detecting oxygen in the atmosphere is important, so too is detecting unmistakable surface water.

But for reasons of both science and detectability, the chemical make-up exoplanet atmospheres is where much biosignature work is being done. The compounds of interest include (but are not limited to) ozone, methane, nitrous oxide, sulfur gases, methyl chloride and less specific atmospheric hazes. All are, or have been, associated with life on Earth, and potentially on other planets and moons as well.

The Schwieterman et al review looks at all these compounds and reports on the findings of researchers who have studied them as possible biosignatures. As a sign of how broadly they cast their net, the citations alone of published biosignature papers number more than 300.

(Sara Seager and William Bains of MIT, both specialists in exoplanet atmospheres, have been compiling a separate and much broader list of potential biosignatures, even many produced in very small quantities on Earth. Bains is a co-author on one of the five biosignature papers for the journal Astrobiology.)

All this work, Schwieterman said, will pay off significantly over time.

“If our goal is to constrain the search for life in our solar neighborhood, we need to know as much as we possibly can so the observatories have the necessary capabilities. We could possibly save hundreds of millions or billions of dollars by constraining the possibilities.”

“The strength of this compilation is the full body of knowledge, putting together what we know in a broad and fast-developing field,” Schwieterman said. ”

He said that there’s such a broad range of possible biosignatures, and so many conditions where some might be more or less probable, that’s it’s essential to categorize and prioritize the information that has been collected (and will be collected in the future.)

“We have a lot of observations recorded here, but they will all have their ambiguities,” he said. “Our goal as scientists will be to take what we know and work to reduce those ambiguities. It’s an enormous task.”

See the full article here .

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About Many Worlds

There are many worlds out there waiting to fire your imagination.

Marc Kaufman is an experienced journalist, having spent three decades at The Washington Post and The Philadelphia Inquirer, and is the author of two books on searching for life and planetary habitability. While the “Many Worlds” column is supported by the Lunar Planetary Institute/USRA and informed by NASA’s NExSS initiative, any opinions expressed are the author’s alone.

This site is for everyone interested in the burgeoning field of exoplanet detection and research, from the general public to scientists in the field. It will present columns, news stories and in-depth features, as well as the work of guest writers.

About NExSS

The Nexus for Exoplanet System Science (NExSS) is a NASA research coordination network dedicated to the study of planetary habitability. The goals of NExSS are to investigate the diversity of exoplanets and to learn how their history, geology, and climate interact to create the conditions for life. NExSS investigators also strive to put planets into an architectural context — as solar systems built over the eons through dynamical processes and sculpted by stars. Based on our understanding of our own solar system and habitable planet Earth, researchers in the network aim to identify where habitable niches are most likely to occur, which planets are most likely to be habitable. Leveraging current NASA investments in research and missions, NExSS will accelerate the discovery and characterization of other potentially life-bearing worlds in the galaxy, using a systems science approach.
The National Aeronautics and Space Administration (NASA) is the agency of the United States government that is responsible for the nation’s civilian space program and for aeronautics and aerospace research.

President Dwight D. Eisenhower established the National Aeronautics and Space Administration (NASA) in 1958 with a distinctly civilian (rather than military) orientation encouraging peaceful applications in space science. The National Aeronautics and Space Act was passed on July 29, 1958, disestablishing NASA’s predecessor, the National Advisory Committee for Aeronautics (NACA). The new agency became operational on October 1, 1958.

Since that time, most U.S. space exploration efforts have been led by NASA, including the Apollo moon-landing missions, the Skylab space station, and later the Space Shuttle. Currently, NASA is supporting the International Space Station and is overseeing the development of the Orion Multi-Purpose Crew Vehicle and Commercial Crew vehicles. The agency is also responsible for the Launch Services Program (LSP) which provides oversight of launch operations and countdown management for unmanned NASA launches. Most recently, NASA announced a new Space Launch System that it said would take the agency’s astronauts farther into space than ever before and lay the cornerstone for future human space exploration efforts by the U.S.

NASA science is focused on better understanding Earth through the Earth Observing System, advancing heliophysics through the efforts of the Science Mission Directorate’s Heliophysics Research Program, exploring bodies throughout the Solar System with advanced robotic missions such as New Horizons, and researching astrophysics topics, such as the Big Bang, through the Great Observatories [Hubble, Chandra, Spitzer, and associated programs. NASA shares data with various national and international organizations such as from the [JAXA]Greenhouse Gases Observing Satellite.

From Many Worlds: “A New Way to Find Signals of Habitable Exoplanets?”

NASA NExSS

Many Worlds

2017-12-04
Marc Kaufman

Scientists propose a new and more indirect way of determining whether an exoplanet has a good, bad or unknowable chance of being habitable. (NASA’s Goddard Space Flight Center/Mary Pat Hrybyk)

The search for biosignatures in the atmospheres of distant exoplanets is extremely difficult and time-consuming work. The telescopes that can potentially take the measurements required are few and more will come only slowly. And for the current and next generation of observatories, staring at a single exoplanet long enough to get a measurement of the compounds in its atmosphere will be a time-consuming and expensive process — and thus a relatively infrequent one.

As a way to potentially improve the chances of finding habitable conditions on those exoplanets that are observed, a new approach has been proposed by a group of NASA scientists.

The novel technique takes advantage of the frequent stellar storms emanating from cool, young dwarf stars. These storms throw huge clouds of stellar material and radiation into space – traveling near the speed of light — and the high energy particles then interact with exoplanet atmospheres and produce chemical biosignatures that can be detected.

The study, titled “Atmospheric Beacons of Life from Exoplanets Around G and K Stars“, recently appeared in Nature Scientific Reports.

“We’re in search of molecules formed from fundamental prerequisites to life — specifically molecular nitrogen, which is 78 percent of our atmosphere,” said Airapetian, who is a solar scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and at American University in Washington, D.C. “These are basic molecules that are biologically friendly and have strong infrared emitting power, increasing our chance of detecting them.”

The thin gauzy rim of the planet in foreground is an illustration of its atmosphere. (NASA’s Goddard Space Flight Center)

So this technique, called a search for “Beacons of Life,” would not detect signs of life per se, but would detect secondary or tertiary signals that would, in effect, tell observers to “look here.”

The scientific logic is as follows:

When high-energy particles from a stellar storm reach an exoplanet, they break the nitrogen, oxygen and water molecules that may be in the atmosphere into their individual components.

Water molecules become hydroxyl — one atom each of oxygen and hydrogen, bound together. This sparks a cascade of chemical reactions that ultimately produce what the scientists call the atmospheric beacons of hydroxyl, more molecular oxygen, and nitric oxide.

For researchers, these chemical reactions are very useful guides. When starlight strikes the atmosphere, spring-like bonds within the beacon molecules absorb the energy and vibrate, sending that energy back into space as heat, or infrared radiation. Scientists know which gases emit radiation at particular wavelengths of light. So by looking at all the radiation coming from the that planet’s atmosphere, it’s possible to get a sense of what chemicals are present and roughly in what amounts..

Forming a detectable amount of these beacons requires a large quantity of molecular oxygen and nitrogen. As a result, if detected these compounds would suggest the planet has an atmosphere filled with biologically friendly chemistry as well as Earth-like atmospheric pressure. The odds of the planet being a habitable world remain small, but those odds do grow.

“These conditions are not life, but are fundamental prerequisites for life and are comparable to our Earth’s atmosphere,” Airapetian wrote in an email.

Stellar storms and related coronal mass ejections are thought to burst into space when magnetic reconnections in various regions of the star. For stars like our sun, the storms become less frequent within a relatively short period, astronomically speaking. Smaller and less luminous red dwarf stars, which are the most common in the universe, continue to send out intense stellar flares for a much longer time.

Vladimir Airapetian is a senior researcher at NASA Goddard and a member of NASA’s Nexus for Exoplanet System Science (NExSS) initiative.

The effect of stellar weather on planets orbiting young stars, including our own four billion years ago, has been a focus of Airapetian’s work for some time.

For instance, Airapetian and Goddard colleague William Danchi published a paper in the journal Nature last year proposing that solar flares warmed the early Earth to make it habitable. They concluded that the high-energy particles also provided the vast amounts of energy needed to combine evenly scattered simple molecules into the kind of complex molecules that could keep the planet warm and form some of the chemical building blocks of life.

In other words, they argue, the solar flares were an essential part of the process that led to us.

What Airapetian is proposing now is to look at the chemical results of stellar flares hitting exoplanet atmospheres to see if they might be an essential part of a life-producing process as well, or of a process that creates a potentially habitable planet.

Airapetian said that he is again working with Danchi, a Goddard astrophysicist, and the team from heliophysics to propose a NASA mission that would use some of their solar and stellar flare findings. The mission being conceived, the Exo Life Beacon Space Telescope (ELBST), would measure infrared emissions of an exoplanet atmosphere using direct imaging observations, along with technology to block the infrared emissions of the host star.

For this latest paper, Airapetian and colleagues used a computer simulation to study the interaction between the atmosphere and high-energy space weather around a cool, active star. They found that ozone drops to a minimum and that the decline reflects the production of atmospheric beacons.

They then used a model to calculate just how much nitric oxide and hydroxyl would form and how much ozone would be destroyed in an Earth-like atmosphere around an active star. Earth scientists have used this model for decades to study how ozone — which forms naturally when sunlight strikes oxygenin the upper atmosphere — responds to solar storms. But the ozone reactions found a new application in this study; Earth is, after all, the best case study in the search for habitable planets and life.

Will this new approach to searching for habitable planets out?

“This is an exciting new proposed way to look for life,” said Shawn Domagal-Goldman, a Goddard astrobiologist not connected with the study. “But as with all signs of life, the exoplanet community needs to think hard about context. What are the ways non-biological processes could mimic this signature?”

A 2012 coronal mass ejection from the sun. Earth is placed into the image to give a sense of the size of the solar flare, but our planet is of course nowhere near the sun. (NASA, Goddard Media Studios)

Today, Earth enjoys a layer of protection from the high-energy particles of solar storms due to its strong magnetic field. However, some particularly strong solar events can still interact with the magnetosphere and potentially wreak havoc on certain technology on Earth.

The National Oceanic and Atmospheric Administration classifies solar storms on a scale of one to five (one being the weakest; five being the most severe). For instance, a storm forecast to be a G3 event means it could have the strength to cause fluctuations in some power grids, intermittent radio blackouts in higher latitudes and possible GPS issues.

This is what can happen to a planet with a strong magnetic field and a sun that is no longer prone to sending out frequent solar flares. Imagine what stellar storms can do when the star is younger and more prone to powerful flaring, and the planet less protected.

Exoplanet scientists often talk of the possibility that a particular planet was “sterilized” by the high-energy storms, and so could never be habitable. But this new research suggests that some stellar storms could have just the opposite effect — making the planet more habitable.

See the full article here.

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About Many Worlds

There are many worlds out there waiting to fire your imagination.

Marc Kaufman is an experienced journalist, having spent three decades at The Washington Post and The Philadelphia Inquirer, and is the author of two books on searching for life and planetary habitability. While the “Many Worlds” column is supported by the Lunar Planetary Institute/USRA and informed by NASA’s NExSS initiative, any opinions expressed are the author’s alone.

This site is for everyone interested in the burgeoning field of exoplanet detection and research, from the general public to scientists in the field. It will present columns, news stories and in-depth features, as well as the work of guest writers.

About NExSS

The Nexus for Exoplanet System Science (NExSS) is a NASA research coordination network dedicated to the study of planetary habitability. The goals of NExSS are to investigate the diversity of exoplanets and to learn how their history, geology, and climate interact to create the conditions for life. NExSS investigators also strive to put planets into an architectural context — as solar systems built over the eons through dynamical processes and sculpted by stars. Based on our understanding of our own solar system and habitable planet Earth, researchers in the network aim to identify where habitable niches are most likely to occur, which planets are most likely to be habitable. Leveraging current NASA investments in research and missions, NExSS will accelerate the discovery and characterization of other potentially life-bearing worlds in the galaxy, using a systems science approach.
The National Aeronautics and Space Administration (NASA) is the agency of the United States government that is responsible for the nation’s civilian space program and for aeronautics and aerospace research.

President Dwight D. Eisenhower established the National Aeronautics and Space Administration (NASA) in 1958 with a distinctly civilian (rather than military) orientation encouraging peaceful applications in space science. The National Aeronautics and Space Act was passed on July 29, 1958, disestablishing NASA’s predecessor, the National Advisory Committee for Aeronautics (NACA). The new agency became operational on October 1, 1958.

Since that time, most U.S. space exploration efforts have been led by NASA, including the Apollo moon-landing missions, the Skylab space station, and later the Space Shuttle. Currently, NASA is supporting the International Space Station and is overseeing the development of the Orion Multi-Purpose Crew Vehicle and Commercial Crew vehicles. The agency is also responsible for the Launch Services Program (LSP) which provides oversight of launch operations and countdown management for unmanned NASA launches. Most recently, NASA announced a new Space Launch System that it said would take the agency’s astronauts farther into space than ever before and lay the cornerstone for future human space exploration efforts by the U.S.

NASA science is focused on better understanding Earth through the Earth Observing System, advancing heliophysics through the efforts of the Science Mission Directorate’s Heliophysics Research Program, exploring bodies throughout the Solar System with advanced robotic missions such as New Horizons, and researching astrophysics topics, such as the Big Bang, through the Great Observatories [Hubble, Chandra, Spitzer, and associated programs. NASA shares data with various national and international organizations such as from the [JAXA]Greenhouse Gases Observing Satellite.

From JPL-Caltech: “Our Living Planet Shapes the Search for Life Beyond Earth”

JPL-Caltech

November 15, 2017
Alan Buis
Jet Propulsion Laboratory, Pasadena, Calif.
818-354-0474
alan.buis@jpl.nasa.gov

Elizabeth Landau
Jet Propulsion Laboratory, Pasadena, Calif.
818-354-6425
Elizabeth.landau@jpl.nasa.gov

Written by Carol Rasmussen
NASA’s Earth Science News Team

Left, an image of Earth from the DSCOVR-EPIC camera. Right, the same image degraded to a resolution of 3 x 3 pixels, similar to what researchers will see in future exoplanet observations. Credit: NOAA/NASA, Stephen Kane

As a young scientist, Tony del Genio of NASA’s Goddard Institute for Space Studies in New York City met Clyde Tombaugh, the discoverer of Pluto.

“I thought, ‘Wow, this is a one-time opportunity,'” del Genio said. “I’ll never meet anyone else who found a planet.”

That prediction was spectacularly wrong. In 1992, two scientists discovered the first planet around another star, or exoplanet, and since then more people have found planets than throughout all of Earth’s preceding history. As of this month, scientists have confirmed more than 3,500 exoplanets in more than 2,700 star systems. Del Genio has met many of these new planet finders.

Del Genio is now co-lead of a NASA interdisciplinary initiative [NEXSS] to search for life on other worlds. This new position as the lead of this project may seem odd to those who know him professionally. Why? He has dedicated decades to studying Earth, not searching for life elsewhere.

We know of only one living planet: our own. But we know it very well. As we move to the next stage in the search for alien life, the effort will require the expertise of planetary scientists, heliophysicists and astrophysicists. However, the knowledge and tools NASA has developed to study life on Earth will also be one of the greatest assets to the quest.

Habitable Worlds

There are two main questions in the search for life: With so many places to look, how can we focus in on the places most likely to harbor life? What are the unmistakable signs of life — even if it comes in a form we don’t fully understand?

“Before we go looking for life, we’re trying to figure out what kinds of planets could have a climate that’s conducive to life,” del Genio said. “We’re using the same climate models that we use to project 21st century climate change on Earth to do simulations of specific exoplanets that have been discovered, and hypothetical ones.”

Del Genio recognizes that life may well exist in forms and places so bizarre that it might be substantially different from Earth. But in this early phase of the search, “We have to go with the kind of life we know,” he said.

Further, we should make sure we use the detailed knowledge of Earth. In particular, we should make sure of our discoveries on life in various environments on Earth, our knowledge of how our planet and its life have affected each other over Earth history, and our satellite observations of Earth’s climate.

Above all else, that means liquid water. Every cell we know of — even bacteria around deep-sea vents that exist without sunlight — requires water.

Life in the Ocean

Research scientist Morgan Cable of NASA’s Jet Propulsion Laboratory in Pasadena, California, is looking within the solar system for locations that have the potential to support liquid water. Some of the icy moons around Saturn and Jupiter have oceans below the ice crust. These oceans were formed by tidal heating, that is, warming of the ice caused by friction between the surface ice and the core as a result of the gravitational interaction between the planet and the moon.

“We thought Enceladus was just boring and cold until the Cassini mission discovered a liquid water subsurface ocean,” said Cable. The water is spraying into space, and the Cassini mission found hints in the chemical composition of the spray that the ocean chemistry is affected by interactions between heated water and rocks at the seafloor. The Galileo and Voyager missions provided evidence that Europa also has a liquid water ocean under an icy crust. Observations revealed a jumbled terrain that could be the result of ice melting and reforming.

As missions to these moons are being developed, scientists are using Earth as a testbed. Just as prototypes for NASA’s Mars rovers made their trial runs on Earth’s deserts, researchers are testing both hypotheses and technology on our oceans and extreme environments.

Cable gave the example of satellite observations of Arctic and Antarctic ice fields, which are informing the planning for a Europa mission. The Earth observations help researchers find ways to date the origin of jumbled ice. “When we visit Europa, we want to go to very young places, where material from that ocean is being expressed on the surface,” she said. “Anywhere like that, the chances of finding evidence of life goes up — if they’re there.”

Water in Space

For any star, it’s possible to calculate the range of distances where orbiting planets could have liquid water on the surface. This is called the star’s habitable zone.

Astronomers have already located some habitable-zone planets, and research scientist Andrew Rushby, of NASA Ames Research Center, in Moffett Field, California, is studying ways to refine the search. Location alone isn’t enough. “An alien would spot three planets in our solar system in the habitable zone [Earth, Mars and Venus],” Rushby said, “but we know that 67 percent of those planets are not very habitable.” He recently developed a simplified model of Earth’s carbon cycle and combined it with other tools to study which planets in the habitable zone would be the best targets to look at for life, considering probable tectonic activity and water cycles. He found that larger rocky planets are more likely than smaller ones to have surface temperatures where liquid water could exist, given the same amount of light from the star.

Renyu Hu, of JPL, refined the search for habitable planets in a different way, looking for the signature of a rocky planet. Basic physics tells us that smaller planets must be rocky and larger ones gaseous, but for planets ranging from Earth-sized to about twice that radius, astronomers can’t tell a large rocky planet from a small gaseous planet. Hu pioneered a method to detect surface minerals on bare-rock exoplanets and defined the atmospheric chemical signature of volcanic activity, which wouldn’t occur on a gas planet.

Vital Signs

When scientists are evaluating a possible habitable planet, “life has to be the hypothesis of last resort,” Cable said. “You must eliminate all other explanations.” Identifying possible false positives for the signal of life is an ongoing area of research in the exoplanet community. For example, the oxygen in Earth’s atmosphere comes from living things, but oxygen can also be produced by inorganic chemical reactions.

Shawn Domagal-Goldman, of NASA’s Goddard Space Flight Center in Greenbelt, Maryland, looks for unmistakable, chemical signs of life, or biosignatures. One biosignature may be finding two or more molecules in an atmosphere that shouldn’t be there at the same time. He uses this analogy: If you walked into a college dorm room and found three students and a pizza, you could conclude that the pizza had recently arrived, because college students quickly consume pizza. Oxygen “consumes” methane by breaking it down in various chemical reactions. Without inputs of methane from life on Earth’s surface, our atmosphere would become totally depleted of methane within a few decades.

Earth as Exoplanet

When humans start collecting direct images of exoplanets, even the closest one will appear as a handful of pixels in the detector – something like the famous “blue dot” image of Earth from Saturn. What can we learn about planetary life from a single dot?

Stephen Kane of the University of California, Riverside, has come up with a way to answer that question using NASA’s Earth Polychromatic Imaging camera on the National Oceanic and Atmospheric Administration’s Deep Space Climate Observatory (DSCOVR).

NASA/DSCOVR

These high-resolution images — 2,000 x 2,000 pixels – document Earth’s global weather patterns and other climate-related phenomena. “I’m taking these glorious pictures and collapsing them down to a single pixel or handful of pixels,” Kane explained. He runs the light through a noise filter that attempts to simulate the interference expected from an exoplanet mission.

DSCOVR takes a picture every half hour, and it’s been in orbit for two years. Its more than 30,000 images are by far the longest continuous record of Earth from space in existence. By observing how the brightness of Earth changes when mostly land is in view compared with mostly water, Kane has been able to reverse-engineer Earth’s rotation rate — something that has yet to be measured directly for exoplanets.

When Will We Find Life?

Every scientist involved in the search for life is convinced it’s out there. Their opinions differ on when we’ll find it.

“I think that in 20 years we will have found one candidate that might be it,” says del Genio. Considering his experience with Tombaugh, he added, “But my track record for predicting the future is not so good.”

Rushby, on the other hand, says, “It’s been 20 years away for the last 50 years. I do think it’s on the scale of decades. If I were a betting man, which I’m not, I’d go for Europa or Enceladus.”

How soon we find a living exoplanet really depends on whether there’s one relatively nearby, with the right orbit and size, and with biosignatures that we are able to recognize, Hu said. In other words, “There’s always a factor of luck.”

See the full article here .

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Jet Propulsion Laboratory (JPL) is a federally funded research and development center and NASA field center located in the San Gabriel Valley area of Los Angeles County, California, United States. Although the facility has a Pasadena postal address, it is actually headquartered in the city of La Cañada Flintridge [1], on the northwest border of Pasadena. JPL is managed by the nearby California Institute of Technology (Caltech) for the National Aeronautics and Space Administration. The Laboratory’s primary function is the construction and operation of robotic planetary spacecraft, though it also conducts Earth-orbit and astronomy missions. It is also responsible for operating NASA’s Deep Space Network.

From astrobites: “Beacons of Life”

astrobites

Nov 14, 2017
Eckhart Spalding

Title: Atmospheric Beacons of Life from Exoplanets Around G and K Stars
Authors: Vladimir S. Airapetian, Charles H. Jackman, Martin Mlynczak, William Danchi, Linda Hunt
First author’s institution: Goddard Space Flight Center and American University


Status: Published in Nature Scientific Reports, open access

Introduction

Once upon a time, the detection of abundant molecular oxygen in an exoplanet’s atmosphere was considered to be a “slam-dunk” indication of a biosphere. O2 is an exhaust gas from the production of glucose, life’s molecular Clif Bar. The heavy, disequilibrium presence of oxygen in the Earth’s atmosphere only exists because lots of biomass keeps pumping it in.

However, as observing capabilities have advanced to the point where we can actually start studying exoplanet atmospheres, the widening theoretical picture has become much more interesting. Would molecular oxygen indicate the presence of life? Well, maybe… and maybe not. It could be generated without life when UV insolation breaks up H2O or CO2 molecules. This is not significant in the Earth’s atmosphere, but today’s paper notes that it could be significant in dry, CO2-dominated atmospheres of planets around M-dwarfs.

Detection and verification of biosignatures will be hard, and not only because false positives will try to fool us. The signals are tiny, and will require long integration times with next-generation space telescopes and extremely large telescopes (ELTs). But those telescopes will be heavily oversubscribed, and observation times will have to be kept down to the absolute minimum.

Therefore, it is to our benefit to be clever and find complementary and easier ways of inferring the presence of a biosphere.

Today’s paper

The authors of today’s paper consider chemistry that is “downstream” from the most direct biomarkers. They are interested in molecules with wide rovibrational absorption or emission bands (molecules can twist, turn, and stretch in ways that correspond to a wide range of energies) because observations will forseeably be limited to low-resolution spectroscopy.

The authors consider a nitrogen-dominated atmosphere, like present-day Earth’s. Nitrogen is handy for life because it can reassemble itself with hydrogen to help form stringy organic molecules. But before that happens, if an active star showers planets with electrons and UV and X-ray photons (XUV), N2 and H2O molecules will be broken up and reassemble into others containing sulfur or deuterium, which in turn join up with O2 to produce nitric oxide (NO).

Fig. 1: The cyclical “beacon” of the Earth’s OH emission as it rises and falls with Solar activity. The two colors indicate emission from day- and nighttime sides. (From Fig. 1 of today’s paper.)

See the full article here .

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What do we do?

Astrobites is a daily astrophysical literature journal written by graduate students in astronomy. Our goal is to present one interesting paper per day in a brief format that is accessible to undergraduate students in the physical sciences who are interested in active research.
Why read Astrobites?

Reading a technical paper from an unfamiliar subfield is intimidating. It may not be obvious how the techniques used by the researchers really work or what role the new research plays in answering the bigger questions motivating that field, not to mention the obscure jargon! For most people, it takes years for scientific papers to become meaningful.
Our goal is to solve this problem, one paper at a time. In 5 minutes a day reading Astrobites, you should not only learn about one interesting piece of current work, but also get a peek at the broader picture of research in a new area of astronomy.