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  • richardmitnick 12:22 pm on January 5, 2019 Permalink | Reply
    Tags: , , , ‘Following the Water’, , , , , Fingerprinting Life, Kepler space telescope, , , , The habitable zone serves as a target selection tool, , , UCO Lick Observatory Mt Hamilton in San Jose California, UCR’s Alternative Earths Astrobiology Center   

    From UC Riverside: “Are We Alone?” 

    UC Riverside bloc

    From UC Riverside

    May 24, 2018
    Sarah Nightingale

    1
    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

    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.

    3
    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.”

    3
    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.

    4
    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

    4
    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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    Please help promote STEM in your local schools.

    Stem Education Coalition

    UC Riverside Campus

    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.

     
  • richardmitnick 11:26 am on November 14, 2018 Permalink | Reply
    Tags: As of September 2018 the combined observatories of the world have detected 3845 exoplanets distributed across 2866 planetary systems of which 636 are multiple planet systems, , , , , From Medium: "A World Apart", , Kepler space telescope, Planetary Habitability Laboratory at Arecibo in Puerto Rico, The first exoplanets were confirmed in 1992 discovered around pulsar PSR B1257+12, The next exoplanetary finding occurred in 1995- a gas giant orbiting 51 Pegasi, There are currently 55 potentially habitable exoplanets out of the thousands of worlds we have thus far detected, Why Earth is unique and what that means for the many exoplanets we are finding in this golden age of astronomy   

    From Medium: “A World Apart” 

    From Medium

    Nov 6, 2018
    Tony Deller

    1
    No image caption or credit.

    Why Earth is unique and what that means for the many exoplanets we are finding in this golden age of astronomy.

    To most of us, our world is simply the place where we live: you’re born, get an education and/or learn a trade, perhaps start a family of your own, pass on some of the knowledge and wisdom you have gained to others, grow old and eventually die. It’s an oversimplification, but that is the common experience of a human on planet Earth. Earth is just where we do “everything”. If you are very lucky, you have opportunities to actually travel around the Earth and visit continents other than the one you were born on, seeing the true vastness of the planet and the variety of its civilizations and biomes. You realize we are many, but we are also one…all of us together on a single sphere of rock, covered with a thin sheen of water, orbiting a massive ball of fire.

    For a long time, the view that humans (and Earth) were the center of the cosmos ruled scientific and philosophic thought. Indeed, great minds like Aristotle and Ptolemy supported this model of the the universe. Though a near-contemporary of those two, Aristarchus of Samos, had proposed a heliocentric view of the universe, his ideas didn’t receive enough support to stick. It took nearly 1800 years for the heliocentric model to become generally accepted, under the scientific leadership of Nicolaus Copernicus.

    The Copernican Revolution, as it is known, gained further support over the succeeding century through the work of Johannes Kepler and Tycho Brahe. Galileo’s telescopic observations of Jupiter’s moons definitely put a nail in the coffin of the geocentric model. Isaac Newton then carried forward with the heliocentric model to show that the Earth and other planets in the Solar System orbited the Sun.

    As telescopic engineering improved, our view of the local universe grew larger and larger. By 1750, Thomas Wright posited that the Milky Way was a tremendous body of stars all held together by gravity and turning about a galactic center.

    Milky Way NASA/JPL-Caltech /ESO R. Hurt

    To us then, the Milky Way was all there was — all we could observe — and so the Milky Way was the universe. It took until 1920, though, when the observations of incredibly faint and distant nebulae by Heber Doust Curtis led to the ultimate acceptance that the Andromeda Nebula (Messier 31) was actually another galaxy.

    Andromeda Galaxy NASA/ESA Hubble

    Milkdromeda -Andromeda on the left-Earth’s night sky in 3.75 billion years-NASA

    Optic technology continued to advance, and more and more galaxies were found throughout the 20th century.

    The first exoplanets were confirmed in 1992, discovered around pulsar PSR B1257+12. These were terrestrial-mass worlds. The next exoplanetary finding occurred in 1995, a gas giant orbiting 51 Pegasi. Since that time, the rate of discovery of exoplanets has accelerated to the point that we can now detect hundreds within the confines of a single project. In 2016, the Kepler space telescope documented 1,284 exoplanets during one such period, over 100 of which are 1.2x Earth mass or smaller, and most likely rocky in nature.

    NASA/Kepler Telescope

    As of September 2018, the combined observatories of the world have detected 3845 exoplanets distributed across 2866 planetary systems, of which 636 are multiple planet systems.

    These worlds are detected using various methods, including: measuring the radial velocity of the (potential) planet’s host star to get an idea of the planet’s mass by how it affects its star;

    Radial Velocity Method-Las Cumbres Observatory


    Radial velocity Image via SuperWasp http:// http://www.superwasp.org/exoplanets.htm

    transit photometry which sees a (potential) planet as it moves between our telescopes and its host star;

    Planet transit. NASA/Ames

    reflection/emission modulations which might show us the heat energy of a (potential) planet; observation of tidal distortions of a host star caused by the gravity of a (potential) massive gas giant; gravitational microlensing in which two stars line up with each other in relation to our observational view from Earth and their gravity distortions act as a magnifying lense that can help us notice planets around one of them; and nearly a dozen other ways.

    Gravitational microlensing, S. Liebes, Physical Review B, 133 (1964): 835

    There are currently 55 potentially habitable exoplanets out of the thousands of worlds we have thus far detected. These are classified into two categories by the Planetary Habitability Laboratory at Arecibo in Puerto Rico: Conservatively habitable worlds are “ more likely to have a rocky composition and maintain surface liquid water (i.e. 0.5 < Planet Radius ≤ 1.5 Earth radii or 0.1 < Planet Minimum Mass ≤ 5 Earth masses, and the planet is orbiting within the conservative habitable zone).” The optimistically habitable planets “are less likely to have a rocky composition or maintain surface liquid water (i.e. 1.5 < Planet Radius ≤ 2.5 Earth radii or 5 < Planet Minimum Mass ≤ 10 Earth masses, or the planet is orbiting within the optimistic habitable zone).”

    3
    Credit: Planetary Habitability Laboratory

    If there are so many potentially habitable exoplanets out there, what is it about Earth that makes it so special?

    Aside from us, that is?

    While the exoplanets we have found so far that exist within the confines of what we have deemed “potentially habitable” may indeed be rocky and orbit at just the right distance from their host stars to maintain liquid water and atmosphere, that doesn’t mean they are habitable, or possess the potential to support Earth life or any life, for that matter. They may not even be suitable candidates for terraforming. That is because the conditions that made and preserved Earth as a safe harbor for life are many and seem to have occurred at precisely the right times throughout the 4.543 billion year history of the planet.

    The factors that allowed life to evolve steadily on Earth — “Goldilocks” factors — include the ones that we use to designate exoplanets as potentially habitable: like them, Earth orbits at just the right distance from the Sun to allow liquid H2O, and Earth formed with such a mass and composition that it became a rocky world as opposed to a gas giant.

    Beyond those primary characteristics, though, Earth possesses other traits that, for the most part, we are still unable to detect on exoplanets.

    Our molten, mostly iron core spins to create a magnetosphere around the planet that deflects excessive solar and cosmic radiation. Our single, relatively large Moon stabilizes our rotation, gives us a 24-hour day, and creates tides that scientists believe were a large driver of evolution.

    We have the ozone layer which adds another protective shield for life against UV light. We have two gas giant worlds in the outer Solar System that have been pulling in a majority of asteroids and comets for billions of years, long before they make it into the inner Solar System to possibly impact Earth.

    We are located at the edge of the Orion spiral arm of our galaxy, far from the much denser, crowded center of the milky Way where asteroids, comets, stellar collisions and supernovae are much more common. The Late Heavy Bombardment, which pounded the Earth with comet impactors roughly 4 billion years ago, seeded our world with just the right amount of water ice to give us vast oceans.

    Our Sun is also quite stable for a star, and luckily isn’t part of a binary star system (which may account for up to 85% of all stars!), which would certainly offer difficulties in the form of gravitational pull from 2 stars and more asteroid activity. The Earth has also been remarkably consistent and stable for billions of years, from its atmospheric and chemical composition to its temperature variations.

    Of all the exoplanets discovered, Earth and its ilk can only exist within a rather narrow band of possibilities:

    4
    Credit: Planetary Habitability Laboratory

    All of these Goldilocks factors added up to a world that has remained a viable habitat for billions of years. Our mineral-rich oceans became a veritable Petri dish in which trillions of generations of single-celled life could mingle and evolve until two such forms merged in a symbiotic relationship that resulted in the first multicellular organism. From there, the diversity of life blossomed uncontrollably.

    That diversity would be one of the reasons life on Earth continued to survive through multiple mass extinction events:

    Cretaceous–Paleogene extinction event — 65 million years ago, 75% species loss

    Triassic–Jurassic extinction event — 199 million to 214 million years ago, 70% species loss

    Permian–Triassic extinction event — 251 million years ago, 96% species loss

    Late Devonian extinction — 364 million years ago, 75% species loss

    Ordovician–Silurian extinction events — 439 million years ago, 86% species loss

    In a strange bit of irony, the earliest two of these great extinctions may have been caused rather directly by the power of evolution on Earth. It’s believed by many scientists that in both of these cases, an extreme amount of plant growth led first to the removal of too much CO2 from the atmosphere and a reverse greenhouse effect, and in the second great extinction to mega algae blooms that depleted the oceans of oxygen.

    The most recent 3 mass extinctions seem to have been caused by a supervolcano eruption, and two massive asteroid impacts.

    There is a sixth mass extinction, generally agreed upon by most paleontologists, that is currently happening: the “holocene extinction event”. It is thought this extinction began at the end of the last ice age (roughly 12,000 years ago) and vastly accelerated with the rise of agriculture, large human civilizations and the Industrial Revolution. Data points to at least 7% of all holocene-era species having already gone extinct directly due to human interaction with our world. Species come into being and go extinct naturally, of course, and this is known as the background rate of extinction. Scientists believe that humans have increased the occurrence of extinctions to possibly as high as 500–1000 times the background rate.

    Reversing this trend needs to be a priority — As the most intelligent species on Earth, we should see ourselves as caretakers of a multi-billion year legacy. We should not, and must not, allow Earth to become a barren hunk of rock due to our inherent drives that often do more harm than good. We are smarter than that. But even if this most recent mass extinction event snowballs and becomes unfixable, it is likely that life will continue to thrive on Earth, whether it be beneath ice or in the ocean’s deepest corners. We need to keep in mind that it is always the creatures at the top of the food chain that die off first in any great extinction.

    And if (and when) Earth does become unlivable for us humans, we should be capable of finding and reaching exoplanets that might become a new home. Hopefully by then we will have become wiser.

    See the full article here .

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    Please help promote STEM in your local schools.

    Stem Education Coalition

    About Medium

    Medium is an online publishing platform developed by Evan Williams, and launched in August 2012. It is owned by A Medium Corporation. The platform is an example of social journalism, having a hybrid collection of amateur and professional people and publications, or exclusive blogs or publishers on Medium, and is regularly regarded as a blog host.

    Williams developed Medium as a way to publish writings and documents longer than Twitter’s 140-character (now 280-character) maximum.

     
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