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  • richardmitnick 11:33 am on August 23, 2015 Permalink | Reply
    Tags: , Astrobiology, ,   

    From astrobio.net: “As Ice Age ended, greenhouse gas rise was lead factor in melting of Earth’s glaciers” 

    Astrobiology Magazine

    Astrobiology Magazine

    Aug 23, 2015
    No Writer Credit

    1
    Improved dating methods reveal that the rise in carbon dioxide levels was the primary cause of the simultaneous melting of glaciers around the globe during the last Ice Age. The new finding has implications for rising levels of man-made greenhouse gases and retreating glaciers today. Courtesy: NSF

    A fresh look at some old rocks has solved a crucial mystery of the last Ice Age, yielding an important new finding that connects to the global retreat of glaciers caused by climate change today, according to a new study by a team of climate scientists.

    For decades, researchers examining the glacial meltdown that ended 11,000 years ago took into account a number of contributing factors, particularly regional influences such as solar radiation, ice sheets and ocean currents.

    But a reexamination of more than 1,000 previously studied glacial boulders has produced a more accurate timetable for the pre-historic meltdown and pinpoints the rise in carbon dioxide – then naturally occurring – as the primary driving factor in the simultaneous global retreat of glaciers at the close of the last Ice Age, the researchers report in the journal Nature Communications.

    “Glaciers are very sensitive to temperature. When you get the world’s glaciers retreating all at the same time, you need a broad, global reason for why the world’s thermostat is going up,” said Boston College Assistant Professor of Earth and Environmental Sciences Jeremy Shakun. “The only factor that explains glaciers melting all around the world in unison during the end of the Ice Age is the rise in greenhouse gases.”

    The researchers found that regional factors caused differences in the precise timing and pace of glacier retreat from one place to another, but carbon dioxide was the major driver of the overall global meltdown, said Shakun, a co-author of the report “Regional and global forcing of glacier retreat during the last deglaciation.”

    “This is a lot like today,” said Shakun. “In any given decade you can always find some areas where glaciers are holding steady or even advancing, but the big picture across the world and over the long run is clear – carbon dioxide is making the ice melt.”

    While 11,000 years ago may seem far too distant for a point of comparison, it was only a moment ago in geological time. The team’s findings fix even greater certainty on scientific conclusions that the dramatic increase in manmade greenhouse gases will eradicate many of the world’s glaciers by the end of this century.

    “This has relevance to today since we’ve already raised CO2 by more than it increased at the end of the Ice Age, and we’re on track to go up much higher this century — which adds credence to the view that most of the world’s glaciers will be largely gone within the next few centuries, with negative consequences such as rising sea level and depleted water resources,” said Shakun.

    The team reexamined samples taken from boulders that were left by the retreating glaciers, said Shakun, who was joined in the research by experts from Oregon State University, University of Wisconsin-Madison, Purdue University and the National Center for Atmospheric Research in Boulder, Colo.

    Each boulder has been exposed to cosmic radiation since the glaciers melted, an exposure that produces the isotope Beryllium-10 in the boulder. Measuring the levels of the isotope in boulder samples allows scientists to determine when glaciers melted and first uncovered the boulders.

    Scientists have been using this process called surface exposure dating for more than two decades to determine when glaciers retreated, Shakun said. His team examined samples collected by multiple research teams over the years and applied an improved methodology that increased the accuracy of the boulder ages.

    The team then compared their new exposure ages to the timing of the rise of carbon dioxide concentration in the atmosphere, a development recorded in air bubbles taken from ice cores. Combined with computer models, the analysis eliminated regional factors as the primary explanations for glacial melting across the globe at the end of the Ice Age. The single leading global factor that did explain the global retreat of glaciers was rising carbon dioxide levels in the air.

    “Our study really removes any doubt as to the leading cause of the decline of the glaciers by 11,000 years ago – it was the rising levels of carbon dioxide in the Earth’s atmosphere,” said Shakun.

    Carbon dioxide levels rose from approximately 180 parts per million to 280 parts per million at the end of the last Ice Age, which spanned nearly 7,000 years. Following more than a century of industrialization, carbon dioxide levels have now risen to approximately 400 parts per million.

    “This tells us we are orchestrating something akin to the end of an Ice Age, but much faster. As the amount of carbon dioxide continues to increase, glaciers around the world will retreat,” said Shakun.

    See the full article here.

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  • richardmitnick 11:22 am on August 9, 2015 Permalink | Reply
    Tags: Astrobiology, , , E.T.,   

    From Daily Galaxy: “New Advances in the Search for Extraterrestrial Life –‘Will It Be Inconceivable to Us?'” 

    Daily Galaxy
    The Daily Galaxy

    August 09, 2015
    No Writer Credit

    1
    No image credit

    A thin layer near the surface of Earth is teeming with life of huge diversity: from micro-organisms to plants and animals, and even intelligent species. Up to now, this forms the only known sample of life in the Universe. We now readily accept that the laws and concepts of physics and chemistry apply throughout the cosmos. Is there a general biology as well: is there life beyond Earth?
    With the Sun just about half-way through its life-time, humankind as we know it is likely to constitute a rather short transient episode, and advanced extra-terrestrial life might be inconceivable to us in its complexity, just as human life is to amoebae.

    Pinpoints of light in the night sky have probably always made humankind speculate about the existence of other worlds, but the presence of planets orbiting stars other than the Sun has become a proven reality only within the last 15 years. While the vast majority of the more than 450 [number is far larger] extra-solar planets that are known to date are gas giants like Jupiter and Saturn, some spectacular discoveries of about 20 planets of less than 10 Earth masses have already indicated that rocky planets with conditions suitable to harbour life are probably rather common.

    One of the big unknowns is how likely it is for life to emerge once all conditions are right. There is no lack of its building blocks; the number of molecules fundamental to Earth’s biochemistry that have already been found in the interstellar medium, planetary atmospheres and on the surfaces of comets, asteroids, meteorites and interplanetary dust particles is surprisingly large. Giant “factories”, where complex molecules are being synthesised, appear to make carbonaceous compounds ubiquitous in the Universe.

    If the genesis of life arises from chemistry with a high probability, one might speculate whether this process occurred more than once on Earth itself, leading to the existence of a terrestrial “shadow biosphere” with a distinct Tree of Life. Moreover, there are several other promising targets within the Solar System, namely Mars, Europa, Enceladus, and, for biochemistry based on a liquid other than water, Titan. Evidence for life is not easy to gather; any chemical footprint needs to be unambiguously characteristic, and to exclude an abiogenic origin. The most powerful probe would result from returning a sample to a laboratory on Earth.

    The year 2010 marks the 50th anniversary of the first search for radio signals originating from other civilizations and up to now all “Search for Extra-Terrestrial Intelligence” (SETI) experiments have provided a negative result.

    Allen Telescope Array
    SETI Institut’s Allen Telescope Array

    SETI@home screensaver
    SETI@home massive personal computer project

    However these have probed only up to about 200 light-years distant, whereas the center of the Milky Way is 25,000 light-years away from us. And, even if there is no other intelligent life in the Milky Way, it could still be hosted in another of the remaining hundreds of billions of other galaxies.

    Advanced efforts are now on the drawing board or already underway for the further exploration of the Solar System and the detection of biomarkers in the atmospheres of extra-solar planets, while searches for signals of extra-terrestrial intelligence are entering a new era with the deployment of the next generation of radio telescopes.

    With the detection of extra-terrestrial life being technically feasible, one needs to address whether perceived societal benefits create an imperative to search for it, or whether such an endeavour may rather turn out to be a threat to our own existence.

    Evolutionary convergence, as seen in the biological history on Earth, suggests that the limited number of solutions to sensory and social organizational problems will make alien civilizations at a comparable stage of evolution not look too different from our own. As historical examples indicate, meeting a civilization similar to ours might actually turn into a disaster.

    Rather than aliens invading Earth, realistically expected detection scenarios will involve microbial organisms and/or extra-terrestrial life at a safe distance that prevents physical contact. As far as exploring other lifeforms is concerned, any applied strategy must exclude biological contamination – not only to protect ourselves, but also to support cosmic biodiversity. No legally enforceable procedures are in place yet, and a broad dialogue on the development of a societal agenda on extra-terrestrial life is required.

    The search for life elsewhere is nothing but a search for ourselves, where we came from, why we are here, and where we will be going. It encompasses many, if not all, of the fundamental questions in biology, physics, and chemistry, but also in philosophy, psychology, religion and the way in which humans interact with their environment and each other. The question of whether we are alone in the Universe still remains unanswered, with no scientific evidence yet supporting one possible outcome or the other. If, however, extra-terrestrial life does exist, an emerging new age of exploration may well allow living generations to witness its detection.

    See the full article here.

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  • richardmitnick 10:59 am on August 6, 2015 Permalink | Reply
    Tags: Astrobiology, ,   

    From NASA Astrobiology: “Researchers Use ‘Seafloor Gardens’ to Switch on Light Bulb” 

    NASA

    NASA

    NASA Astrobiology Institute

    Aug. 5, 2015
    Whitney Clavin 818-354-4673
    Jet Propulsion Laboratory, Pasadena, Calif.
    Whitney.clavin@jpl.nasa.gov

    1
    This photo simulation shows a laboratory-created “chemical garden,” which is a chimney-like structure found at bubbling vents on the seafloor. Some researchers think life on Earth might have got its start at structures like these billions of years ago, partly due to their ability to transfer electrical currents — an essential trait of life as we know it. The battery-like property of these chemical gardens was demonstrated by linking several together in series to light an LED (light-emitting diode) bulb. In this photo simulation, the bulb is not really attached to the chimney.
    The chimney membranes are made of iron sulfides and iron hydroxides, geologic materials that conduct electrons. Image credit: NASA/JPL-Caltech

    One of the key necessities for life on our planet is electricity. That’s not to say that life requires a plug and socket, but everything from shrubs to ants to people harnesses energy via the transfer of electrons — the basis of electricity. Some experts think that the very first cell-like organisms on Earth channeled electricity from the seafloor using bubbling, chimney-shaped structures, also known as chemical gardens.

    In a new study, researchers report growing their own tiny chimneys in a laboratory and using them to power a light bulb. The findings demonstrate that the underwater structures may have indeed given an electrical boost to Earth’s very first life forms.

    2
    A laboratory-created “chemical garden” made of a combination of black iron sulfide and orange iron hydroxide/oxide is shown in this photo. Chemical gardens are a nickname for chimney-like structures that form at bubbling vents on the seafloor. Some researchers think that life may have originated at structures like these billions of years ago.

    “These chimneys can act like electrical wires on the seafloor,” said Laurie Barge of NASA’s Jet Propulsion Laboratory, Pasadena, California, lead author of a new paper on the findings in the journal Angewandte Chemie International Edition. “We’re harnessing energy as the first life on Earth might have.”

    3
    This image from the floor of the Atlantic Ocean shows a collection of limestone towers known as the “Lost City.” Alkaline hydrothermal vents of this type are suggested to be the birthplace of the first living organisms on the ancient Earth.
    Credits: D. Kelley and M. Elend/University of Washington

    The findings are helping researchers put together the story of life on Earth, starting with the first chapter of its origins. How life first took root on our nascent planet is a topic riddled with many unanswered chemistry questions. One leading theory for the origins of life, called the alkaline vent hypothesis, is based on the idea that life sprang up underwater with the help of warm, alkaline (as opposed to acidic) chimneys.

    Chimneys naturally form on the seafloor at hydrothermal vents. They range in size from inches to tens of feet (centimeters to tens of meters), and they are made of different types of minerals with, typically, a porous structure. On early Earth, these chimneys could have established electrical and proton gradients across the thin mineral membranes that separate their compartments. Such gradients emulate critical life processes that generate energy and organic compounds.

    “Life doesn’t want to get electrocuted, but needs just the right amount of electricity,” said Michael Russell of JPL, a co-author of the study. “This new experiment confirms what that amount of electricity is — just under a volt.” Russell first proposed the alkaline vent hypothesis in 1989, and even predicted the existence of alkaline vent chimneys more than a decade before they were actually discovered in the Atlantic Ocean and dubbed “The Lost City.”

    Previously, researchers at the University of Tokyo and the Japan Agency for Marine-Earth Science and Technology recorded electricity in “black smoker” vent chimneys in the Okinawa Trough in Japan. Black smokers are acidic — and hotter and harsher — than alkaline vents.

    The new study demonstrates that laboratory chimneys similar to alkaline vents on early Earth had enough electricity to do something useful — in this case power an LED (light-emitting diode) light bulb. The researchers connected four of the chemical gardens, submerged in iron-containing fluids, to turn on one light bulb. The process took months of patient laboratory work by Barge and Russell’s team, with the help of an undergraduate student intern at JPL, Yeghegis “Lily” Abedian.

    “I remember when Lily told me the light bulb had turned on. It was shocking,” said Barge (while admitting she likes a good pun).

    The scientists hope to do the experiment again using different materials for their laboratory chimneys. In the current study, they made chimneys of iron sulfide and iron hydroxide, geological materials that can conduct electrons. Future experiments can assess the electrical potential of additional materials thought to have been present in Earth’s early oceans and hydrothermal vents, such as molybdenum, nickel, hydrogen and carbon dioxide.

    “With the right recipe, maybe one chimney alone will be able to light the LED – or instead, we could use that electrochemical energy to power other reactions,” said Barge. “We can also start simulating higher temperature and pressures that occur at hydrothermal vents.”

    Materials or other energy sources thought to have been involved in the possible development of life on other planets and moons can be tested too, such as those on early Mars, or icy worlds like Jupiter’s moon Europa.

    The electrical needs of life’s first organisms are only one of many puzzles. Other researchers are trying to figure out how organic materials, such as DNA, might have assembled from scratch. The ultimate goal is to fit all the pieces together into one amazing story of life’s origins.

    The JPL research team is part of the Icy Worlds team of the NASA Astrobiology Institute, based at NASA’s Ames Research Center in Moffett Field, California. The Icy Worlds team is led by Isik Kanik of JPL.

    JPL is managed by the California Institute of Technology in Pasadena for NASA.

    For more information about the NASA Astrobiology Institute, visit:

    http://astrobiology.nasa.gov/nai

    See the full article here.

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    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.

     
  • richardmitnick 2:08 pm on July 29, 2015 Permalink | Reply
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    From astrobio.net: “‘Carbon sink’ detected underneath world’s deserts” 

    Astrobiology Magazine

    Astrobiology Magazine

    Jul 29, 2015
    No Writer Credit

    1
    Scientists followed the journey of water through the Tarim Basin from the rivers at the edge of the valley to the desert aquifers under the basin. They found that as water moved through irrigated fields, the water gathered dissolved carbon and moved it deep underground. Credit: Yan Li

    The world’s deserts may be storing some of the climate-changing carbon dioxide emitted by human activities, a new study suggests. Massive aquifers underneath deserts could hold more carbon than all the plants on land, according to the new research.

    Humans add carbon dioxide to the atmosphere through fossil fuel combustion and deforestation. About 40 percent of this carbon stays in the atmosphere and roughly 30 percent enters the ocean, according to the University Corporation for Atmospheric Research. Scientists thought the remaining carbon was taken up by plants on land, but measurements show plants don’t absorb all of the leftover carbon. Scientists have been searching for a place on land where the additional carbon is being stored—the so-called “missing carbon sink.”

    The new study suggests some of this carbon may be disappearing underneath the world’s deserts – a process exacerbated by irrigation. Scientists examining the flow of water through a Chinese desert found that carbon from the atmosphere is being absorbed by crops, released into the soil and transported underground in groundwater—a process that picked up when farming entered the region 2,000 years ago.

    Underground aquifers store the dissolved carbon deep below the desert where it can’t escape back to the atmosphere, according to the new study.

    The new study estimates that because of agriculture roughly 14 times more carbon than previously thought could be entering these underground desert aquifers every year. These underground pools that taken together cover an area the size of North America may account for at least a portion of the “missing carbon sink” for which scientists have been searching.

    “The carbon is stored in these geological structures covered by thick layers of sand, and it may never return to the atmosphere,” said Yan Li, a desert biogeochemist with the Chinese Academy of Sciences in Urumqi, Xinjiang, and lead author of the study accepted for publication in Geophysical Research Letters, a journal of the American Geophysical Union. “It is basically a one-way trip.”

    Knowing the locations of carbon sinks could improve models used to predict future climate change and enhance calculations of the Earth’s carbon budget, or the amount of fossil fuels humans can burn without causing major changes in the Earth’s temperature, according to the study’s authors.

    Although there are most likely many missing carbon sinks around the world, desert aquifers could be important ones, said Michael Allen, a soil ecologist from the Center for Conservation Biology at the University of California-Riverside who was not an author on the new study.

    If farmers and water managers understand the role heavily-irrigated inland deserts play in storing the world’s carbon, they may be able to alter how much carbon enters these underground reserves, he said.

    “This means [managers] can take practical steps that could play a role in addressing carbon budgets,” said Allen.

    2
    Researchers gathered groundwater flowing under the desert sands. The amount of carbon carried by this underground flow increased quickly when the Silk Road, which opened the region to farming, began 2,000 years ago. Credit: Yan Li

    Examining desert water

    To find out where deserts tucked away the extra carbon, Li and his colleagues analyzed water samples from the Tarim Basin, a Venezuela-sized valley in China’s Xinjiang region. Water draining from rivers in the surrounding mountains support farms that edge the desert in the center of the basin.

    The researchers measured the amount of carbon in each water sample and calculated the age of the carbon to figure out how long the water had been in the ground.

    The study shows the amount of carbon dioxide dissolved in the water doubles as it filters through irrigated fields. The scientists suggest carbon dioxide in the air is taken up by the desert crops. Some of this carbon is released into the soil through the plant’s roots. At the same time, microbes also add carbon dioxide to the soil when they break down sugars in the dirt. In a dry desert, this gas would work its way out of the soil into the air. But on arid farms, the carbon dioxide emitted by the roots and microbes is picked up by irrigation water, according to the new study.

    In these dry regions, where water is scarce, farmers over-irrigate their land to protect their crops from salts that are left behind when water used for farming evaporates. Over-irrigating washes these salts, along with carbon dioxide that is dissolved in the water, deeper into the earth, according to the new study.

    Although this process of carbon burial occurs naturally, the scientists estimate that the amount of carbon disappearing under the Tarim Desert each year is almost 12 times higher because of agriculture. They found that the amount of carbon entering the desert aquifer in the Tarim Desert jumped around the time the Silk Road, which opened the region to farming, begin to flourish.

    After the carbon-rich water flows down into the aquifer near the farms and rivers, it moves sideways toward the middle of the desert, a process that takes roughly 10,000 years.

    Any carbon dissolved in the water stays underground as it makes its way through the aquifer to the center of the desert, where it remains for thousands of years, according to the new study.

    Estimating carbon storage

    Based on the various rates that carbon entered the desert throughout history, the study’s authors estimate 20 billion metric tons (22 billion U.S. tons) of carbon is stored underneath the Tarim Basin desert, dissolved in an aquifer that contains roughly 10 times the amount of water held in the North American Great Lakes.

    The study’s authors approximate the world’s desert aquifers contain roughly 1 trillion metric tons (1 trillion U.S. tons) of carbon—about a quarter more than the amount stored in living plants on land.

    Li said more information about water movement patterns and carbon measurements from other desert basins are needed to improve the estimate of carbon stored underneath deserts around the globe.

    Allen said the new study is “an early foray” into this research area. “It is as much a call for further research as a definitive final answer,” he said.

    See the full article here.

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  • richardmitnick 7:32 pm on April 9, 2015 Permalink | Reply
    Tags: Astrobiology, , ,   

    From astrobio.net: “Can we find an ancient Earth-like planet with a dying biosphere?” 

    Astrobiology Magazine

    Astrobiology Magazine

    Apr 9, 2015
    Amanda Doyle

    1
    The life cycle of a solar-like star shows how our Sun will expand into a red giant. Credit: ESO/M. Kornmesser

    Our Sun will evolve into a red giant star billions of years from now. The increased heat from the expanding Sun will scorch the Earth with dire effects to life. Climate models can be used to predict how this will happen, but, of course, this cannot be tested out on Earth.

    Jack O’Malley-James of the Institute for Pale Blue Dots at Cornell University, along with colleagues, have been calculating the chances of discovering an old-Earth analog approaching the end of its habitable lifetime. This follows his work on Swansong Biospheres in which the potential bio-signatures of a dying world were assessed. The new paper, In Search of Future Earths: Assessing the possibility of finding Earth analogues in the later stages of their habitable lifetimes, has been accepted for publication in the journal Astrobiology and is available in preprint.

    The far future Earth

    Searches are already in place to find Earth’s twin, a planet with a similar mass and radius as the Earth and orbiting at the same distance as the Earth does from the Sun. However, finding an equivalent of Earth’s much older cousin involves a different set of criteria.

    The “habitable zone” is defined as the region where liquid water can exist on the surface of a planet. Habitable zones move outwards as a star ages, so a planet that was in the zone when the star was younger may not necessarily remain there. An old Earth analogue is one that has been in the star’s habitable zone for the entire main sequence lifetime of the star, known as the continuously habitable zone. As the purpose is to study planets in the final stages of habitability, a far future Earth would also have to be approaching the inner edge of the habitable zone.

    2
    The habitable zone (in blue) extends to greater distances for stars hotter than the Sun. Similarly, the habitable zone will move outwards as our Sun becomes a red giant. The continuously habitable zone is a smaller region where a planet can remain habitable throughout the main sequence lifetime of the star. Credit: Wikimedia

    As up to one-third of main sequence solar-like stars are thought to be in the later stages of their evolution, it is feasible that old Earth analogues could be detected. If any of these planets exist in the solar neighborhood, then they would be excellent candidates for future space telescopes with the capability to characterize a planet’s atmosphere from its spectrum.

    Searching nearby

    There are six solar-like stars within 10 parsecs of the Sun that are old enough to harbor an old Earth analogue.

    3
    A parsec is the distance from the Sun to an astronomical object that has a parallax angle of one arcsecond (the diagram is not to scale).

    A parsec is the equivalent of 3.26 light years. O’Malley-James calculated the location of the habitable zone for each star over its entire lifetime. He then placed hypothetical planets in each system at a distance where the planet could remain habitable for billions of years. The temperature changes on the planet over the main sequence lifetime of the star can be modeled by comparing the predicted incoming and outgoing radiation.

    The paper concludes that if Earth-like planets existed around these stars, then the one around 61 Vir would be at the right stage of its lifetime to be considered a far future Earth. Such a planet might be home to a declining microbial population, assuming that life evolved there in a similar manner to the Earth. This hypothetical planet would be akin to the stage in future Earth’s lifetime when the temperature has risen too high for complex life to survive, and microbes are the last lifeforms to cling to existence. Other stars could host planets similar to future Earth where only extremophile microbial life remains in a few select niches, however these biosignatures would be much more difficult to detect than the declining microbial biosphere.

    A Galaxy Teeming with Earth-like Planets?

    If an Earth-like planet existed around 61 Vir, it would provide a good opportunity to study the far future Earth. But what are the actual chances of such planets existing?

    O’Malley-James used previous studies by other scientists in order to find out. One study, based on the number of planets found by NASA’s Kepler mission, predicts that 8.6 percent of solar-like stars could harbor an Earth-like planet orbiting in the habitable zone.

    NASA Kepler Telescope
    Kepler

    A solar-like star is one that is of a similar temperature and mass as our own Star. There are 276 stars like our Sun within 100 parsecs, around half of which are older than six billion years. This means that there should be 11 potential targets.

    3
    61 Vir as seen with a 12.5″ telescope with a field of view of 45.1 arc minutes. Credit: Kevin Heider

    However, another study showed that terrestrial planets are more likely to form less than one astronomical unit (AU), the distance between the Sun and the Earth) from the star. From the six example stars that O’Malley-James studied, the continuously habitable zone is located slightly further from the star than this. Combining these results indicates that there would actually only be one potential old-Earth analogue within the solar neighborhood.

    “It turned out that these planets are probably not that common at all, so in reality any habitable planets in the 61 Vir system will probably not resemble an older version of Earth,” said O’Malley-James. “This study highlights that finding replicas of our own world, in terms of the diversity and complexity of life, is going to be a much harder task than simply finding life.”

    Yet while there may only be one potential old-Earth analogue close enough to be studied in detail, there could still be thousands more in the distant reaches of our Galaxy.

    See the full article here.

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  • richardmitnick 2:46 pm on March 7, 2015 Permalink | Reply
    Tags: , Astrobiology, ,   

    From astrobio.net: “NASA Ames Reproduces the Building Blocks of Life in Laboratory” 

    Astrobiology Magazine

    Astrobiology Magazine

    Mar 7, 2015
    No Writer Credit

    1
    Left to right: Ames scientists Michel Nuevo, Christopher Materese and Scott Sandford reproduce uracil, cytosine, and thymine, three key components of our hereditary material, in the laboratory. Image Credit: NASA/ Dominic Hart

    NASA scientists studying the origin of life have reproduced uracil, cytosine, and thymine, three key components of our hereditary material, in the laboratory. They discovered that an ice sample containing pyrimidine exposed to ultraviolet radiation under space-like conditions produces these essential ingredients of life.

    Pyrimidine is a ring-shaped molecule made up of carbon and nitrogen and is the central structure for uracil, cytosine, and thymine, which are all three part of a genetic code found in ribonucleic (RNA) and deoxyribonucleic acids (DNA). RNA and DNA are central to protein synthesis, but also have many other roles.

    “We have demonstrated for the first time that we can make uracil, cytosine, and thymine, all three components of RNA and DNA, non-biologically in a laboratory under conditions found in space,” said Michel Nuevo, research scientist at NASA’s Ames Research Center, Moffett Field, California. “We are showing that these laboratory processes, which simulate conditions in outer space, can make several fundamental building blocks used by living organisms on Earth.”

    An ice sample is deposited on a cold (approximately –440 degrees Fahrenheit) substrate in a chamber, where it is irradiated with high-energy ultraviolet (UV) photons from a hydrogen lamp. The bombarding photons break chemical bonds in the ices and break down the ice’s molecules into fragments that then recombine to form new compounds, such as uracil, cytosine, and thymine.

    2
    Pyrimidine is a ring-shaped molecule made up of carbon and nitrogen and is the central structure for uracil, cytosine, and thymine, which are found in RNA and DNA. Image Credit: NASA

    NASA Ames scientists have been simulating the environments found in interstellar space and the outer Solar System for years. During this time, they have studied a class of carbon-rich compounds, called polycyclic aromatic hydrocarbons (PAHs), that have been identified in meteorites, and which are the most common carbon-rich compound observed in the universe. PAHs typically are structures based on several six-carbon rings that resemble fused hexagons, or a piece of chicken wire.

    The molecule pyrimidine is found in meteorites, although scientists still do not know its origin. It may be similar to the carbon-rich PAHs, in that it may be produced in the final outbursts of dying, giant red stars, or formed in dense clouds of interstellar gas and dust.

    “Molecules like pyrimidine have nitrogen atoms in their ring structures, which makes them somewhat wimpy. As a less stable molecule, it is more susceptible to destruction by radiation, compared to its counterparts that don’t have nitrogen,” said Scott Sandford, a space science researcher at Ames. “We wanted to test whether pyrimidine can survive in space, and whether it can undergo reactions that turn it into more complicated organic species, such as the nucleobases uracil, cytosine, and thymine.”

    5
    The ring-shaped molecule pyrimidine is found in cytosine and thymine. Image Credit: NASA

    In theory, the researchers thought that if molecules of pyrimidine could survive long enough to migrate into interstellar dust clouds, they might be able to shield themselves from destructive radiation. Once in the clouds, most molecules freeze onto dust grains (much like moisture in your breath condenses on a cold window during winter).

    These clouds are dense enough to screen out much of the surrounding outside radiation of space, thereby providing some protection to the molecules inside the clouds.

    Scientists tested their hypotheses in the Ames Astrochemistry Laboratory. During their experiment, they exposed the ice sample containing pyrimidine to ultraviolet radiation under space-like conditions, including a very high vacuum, extremely low temperatures (approximately –440 degrees Fahrenheit), and harsh radiation.

    They found that when pyrimidine is frozen in ice mostly consisting of water, but also ammonia, methanol, or methane, it is much less vulnerable to destruction by radiation than it would be if it were in the gas phase in open space. Instead of being destroyed, many of the molecules took on new forms, such as the RNA/DNA components uracil, cytosine, and thymine, which are found in the genetic make-up of all living organisms on Earth.

    “We are trying to address the mechanisms in space that are forming these molecules. Considering what we produced in the laboratory, the chemistry of ice exposed to ultraviolet radiation may be an important linking step between what goes on in space and what fell to Earth early in its development,” said Christopher Materese, another researcher at NASA Ames who has been working on these experiments.

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    An ice sample is held at approximately -440 degrees Fahrenheit in a vacuum chamber, where it is irradiated with high energy UV photons from a hydrogen lamp. The bombarding photons break chemical bonds in the ice samples and result in the formation of new compounds, such as uracil. Image Credit: NASA/Dominic Hart

    “Nobody really understands how life got started on Earth. Our experiments suggest that once the Earth formed, many of the building blocks of life were likely present from the beginning. Since we are simulating universal astrophysical conditions, the same is likely wherever planets are formed,” says Sandford.

    Additional team members who helped perform some of the research are Jason Dworkin, Jamie Elsila, and Stefanie Milam, three NASA scientists at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.

    The research was funded by the NASA Astrobiology Institute (NAI) and the NASA Origins of Solar Systems Program. The NAI is a virtual, distributed organization of competitively-selected teams that integrates and funds astrobiology research and training programs in concert with the national and international science communities.

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  • richardmitnick 7:03 pm on February 9, 2015 Permalink | Reply
    Tags: Astrobiology, , ,   

    From astrobio: “Planets Orbiting Red Dwarfs May Stay Wet Enough for Life” 

    Astrobiology Magazine

    Astrobiology Magazine

    Feb 9, 2015
    Charles Q. Choi

    1
    Oceans currents would transport heat to the dark side of tidally-locked exoplanets. Image Credit: Lynette Cook

    Small, cold stars known as red dwarfs are the most common type of star in the Universe, and the sheer number of planets that may exist around them potentially make them valuable places to hunt for signs of extraterrestrial life.

    However, previous research into planets around red dwarfs suggested that while they may be warm enough to host life, they might also completely dry out, with any water they possess locked away permanently as ice. New research published on the topic finds that these planets may stay wet enough for life after all. The scientists detailed their findings online on November 12 in The Astrophysical Journal Letters.

    Red dwarfs, also known as M stars, are roughly one-fifth as massive as the Sun and up to 50 times fainter. These stars comprise up to 70 percent of the stars in the cosmos, and NASA’s Kepler space observatory has discovered that at least half of these stars host rocky planets that are one-half to four times the mass of Earth.

    NASA Kepler Telescope
    Kepler

    Red dwarf planets are potentially key places to search for life as we know it, not just because there are so many of them, but also because of their incredible longevity. Unlike our Sun, which will die in a few billion years, red dwarfs will take trillions of years to burn through their fuel, significantly longer than the age of the Universe, which is less than 14 billion years old. This longevity potentially gives red dwarfs a great deal more time for life to evolve around them.

    Research into whether a distant world might host life as we know it usually focuses on whether or not it has liquid water, since there is life virtually everywhere there is liquid water on Earth, even miles underground. Scientists typically concentrate on habitable zones, the area around a star where it is neither too hot for all its surface water to boil away, nor too cold enough for all its surface water to freeze.

    Recent findings suggest that planets in the habitable zones of red dwarf stars could accumulate significant amounts of water. In fact, each planet could possess about 25 times more water than Earth.

    The habitable zones of red dwarfs are close to these stars because of how dim they are, often closer than the distance Mercury orbits the Sun. This closeness makes them appealing to astrobiologists, since planets near their stars cross in front of them more often, making them easier to detect than planets that orbit farther away.

    However, when a planet orbits very near a star, the star’s gravitational pull can force the world to become “tidally locked” to it. When a planet is tidally locked to its star, it will always show the same side to its star, just as the Moon always shows the same side to Earth. This causes the planet to have one permanent day side and one permanent night side.

    3

    The extremes of heat and cold that tidally locked planets experience could make them profoundly different from Earth. For example, prior research speculated the dark sides of tidally locked planets would become so cold that any water there would freeze. Sunlight would make water on the sunlit side evaporate, and this water vapor could get carried by air currents to the night sides, eventually leading to sheets of ice miles thick on the night sides and removing all water from the sunlit sides. Life as we know it probably could not develop on the day sides of such planets. Although they would have sunlight for photosynthesis, they would have no water to serve as the primordial soup for life to swim in.

    To see how habitable tidally-locked planets really are, scientists devised a 3D global climate model of planets that simulated interactions between the atmosphere, ocean, sea ice, and land, as well as a 3-D model of ice sheets large enough to cover entire continents. They also simulated a red dwarf with a temperature of about 5,660 degrees Fahrenheit (3,125 degrees Celsius), and investigated whether all the water on these planets would indeed get trapped on their night sides.

    “I’ve been interested in trying to make calculations relevant for M-star planet habitability since being convinced by astronomers that these types of planets will likely be closest (in proximity) to Earth,” said study co-author Dorian Abbot, a geoscientist at the University of Chicago.

    For instance, the nearest known star to the Sun, Proxima Centauri, is a red dwarf, and it remains uncertain whether or not it has a planet. The possibility that red dwarf planets might be relatively near to Earth “means that anything geoscientists can tell astronomers about habitability of these planets will be essential for planning future missions.”

    The researchers simulated planets of Earth’s size and gravity that experienced between 63 percent and 77 percent as much sunlight as Earth. They also modeled a super-Earth planet 50 percent wider than Earth with 38 percent stronger gravity, because astronomers have discovered super-Earth worlds around red dwarfs. For instance, Gliese 667Cb, a super-Earth at least 4.5 times the mass of Earth, orbits Gliese 667C, a red dwarf about 22 light years from Earth. They set this super-Earth on an orbit where it received about two-thirds as much as sunlight as Earth.

    The researchers modeled three different arrangements of continents for all these planets. One was a water world with no continents and global oceans of varying depths. Another involved a supercontinent covering the night side and an ocean covering the day side. The last mimicked Earth’s configuration of continents. The planets also had atmospheres similar to Earth’s, but the researchers also tested lower levels of the greenhouse gas, carbon dioxide, which traps heat and helps keep planets warm.

    When it came to super-Earths covered entirely in water, and super-Earths with continental arrangements like Earth’s, the researchers found it was unlikely that all their water would get trapped on their night sides.

    “This is because surface winds transport sea ice to the day side where it is melted easily,” said lead study author Jun Yang at the University of Chicago.

    Moreover, ocean currents transport heat from the day side to the night side on these planets.

    “Ocean heat transport strongly influences the climate and sea ice thickness on our Earth,” Yang said. “We found this may also work on exoplanets.”

    If a super-Earth has very large continents covering most of its night side, the scientists discovered ice sheets of at least 3,300 feet (1,000 meters) thick could grow on its night side. However, the day sides of these super-Earths would dry out completely only if they received less geothermal heat from volcanic activity than Earth, and had 10 percent of the amount of water on Earth’s surface or less. Similar results were seen with Earth-sized planets.

    “The important implication is that it may be easier than previously thought to keep liquid water on the dayside of a tidally locked planet, where photosynthesis is possible,” Abbot said. “There are many issues that will affect the habitability of M-star planets, but our results suggest at least that water-trapping on the night side will only be a problem for relatively dry planets with large continents on their nightside and relatively low geothermal heat flux.”

    Based on present and near-future technology, Yang said it would be very difficult for astronomers to gauge how thick the sea ice or the ice sheets are on the night sides of red dwarf planets and test whether their models are correct. Still, using current and upcoming technology “it may be possible to know whether the day sides are dry or not,” Yang said.

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  • richardmitnick 4:39 pm on January 23, 2015 Permalink | Reply
    Tags: Astrobiology, , , U Montana   

    From SPACE.com: “How Did Life Become Complex, and Could It Happen Beyond Earth?” 

    space-dot-com logo

    SPACE.com

    January 20, 2015
    Elizabeth Howell, Astrobiology Magazine

    When astrobiologists contemplate life on nearby planets or moons, they often suggest such life would be simple. Instead of there being some kind of multicellular organism on, say, Jupiter’s moon Europa, scientists instead aim to find something more like a microbe.

    But from such simple life, more complex lifeforms could eventually come to be. That’s what happened here on planet Earth, and that’s what could happen in other locations as well. How did the chemistry evolve to get life to where we are today? What transitions took place?

    1
    Studying areas such as Titan, a moon of Saturn (foreground) can give researchers ideas about how chemistry eventually created life.
    Credit: NASA/JPL-Caltech/Space Science Institute

    Frank Rosenzweig, an evolutionary geneticist at the University of Montana, is looking into such questions over the next five years with funding from the NASA Astrobiology Institute. His lab studies how life evolves “complex traits,” factors that influence everything from lifespan to biodiversity.

    “Over my career, I’ve been interested in what are the genetic bases of adaptation and how do complex communities evolve from single clones,” Rosenzweig said. “Related to these questions are others such as how do the genetic ‘starting point’ and ecological setting influence the tempo and trajectory of evolutionary change.”

    Shopping for life in the Solar System

    Complex life is only known to exist on Earth, but scientists aren’t ruling out other locations in the Solar System. Our understanding of life’s evolution could be informed by studying the Saturnian moon Titan, whose hydrocarbon chemistry is considered a precursor to a living system. Researchers recently tried to replicate a substance in Titan’s atmosphere called tholins, which are organic aerosols created from solar radiation hitting the methane and nitrogen atmosphere.

    2
    Tholins, complex organic molecules fundamental to prebiotic chemistry, are apparently forming at a much higher altitude, and in different ways than expected, in Titan’s atmosphere.

    Understanding how tholins and other substances are formed on Titan could give researchers a picture of how early Earth evolved life. Also, studying how Earthly life-forms and their biochemical precursors evolved from simple subunits to successively more complex and interdependent systems could give hints of how life might evolve on other moons or planets.

    On Earth, examples of these transitions include collections of single proteins evolving into protein networks. For example, single-celled bacteria evolve into eukaryotic cells that contain two, or even three genomes. Also, competing microbes come together to form cooperative systems, such as microbial mats in hot springs and microbial biofilms lining the human gut. Each of these transitions results in increased bio-complexity, interdependence and a certain degree of autonomy for a new whole that is more than the sum of its parts.

    Rosenzweig’s research developed out of previous NASA grants over the past six years, and from his being a panelist reviewing team-based proposals for the NASA Astrobiology Institute.

    “There is, and still needs to be a lot of work done on chemical evolution, prebiotic (pre-life) evolution, extreme environments and bio-signatures,”Rosenzweig said. “It struck me that it might be worthwhile trying to convince NASA to add to its research portfolio a set of proposals focused on understanding the genetic basis underlying major evolutionary transitions that have led to higher-order complexity”

    As such, Rosenzweig’s new research will focus on four areas where a complex system has arisen from simpler elements: metabolism, the eukaryotic cell, mutualism (co-operating species) and multicellularity. He will also look into a fifth area — mutations and gene interactions — that critically determines how quickly such complex systems can arise. He believes that lab experiments aimed at replicating key aspects of the evolution of life on Earth can better inform how we search in life-friendly locations on Mars, Europa, Saturn’s moon Titan, or elsewhere.

    Rosenzweig plans to have eight different teams focusing on questions of evolution and changes from simple to more complex life. To integrate his teams’ experimental results into a broader framework he recruited theoreticians in the areas of population genetics and statistical physics.

    Rosenzweig’s previous NASA funding came from the Exobiology and Evolutionary Biology Program. The first project, initiated in 2007, examined how genetic material (or genomes) evolve in yeast species that were cultured under limited resources. A second project, initiated in 2010, is investigating how founder cells in E. coli genotypes, and the environment in which they evolve, influence the diversity and stability of subsequent populations.

    3
    A species of yeast (Saccharomyces cerevisiae) seen in a scanning electrograph image.
    Credit: NASA

    The first project led to an unexpected finding: stress may increase the frequency with which genome sequences are rearranged. Stress introduces new chromosomal variants into the species; population that could prove beneficial under challenging circumstances. Indeed, previous studies have indicated that new chromosomal variants are stress resistant. In 2013, Rosenzweig’s team, led by University of Montana research professor Eugene Kroll, began studying how yeast cultures respond to starvation.

    This new line of inquiry has already led to one major publication entitled, Starvation-associated genome restructuring can lead to reproductive isolation in yeast, which was published in PLoS One in 2013. Therein, Kroll and Rosenzweig further show that yeast containing stress-adaptive genomic rearrangements become “reproductively isolated” from their ancestors, suggesting that, at least in lower fungi, geographic isolation may not be required to generate new species. A new project through NASA’s Exobiology and Evolutionary Biology Program, awarded Summer 2014, will enable the team to tease out the genetic mechanisms that underlie adaptation and reproductive isolation in starved yeast.

    A distinguishing feature of this research, Rosenzweig notes, is that whereas most studies look at species’ performance in relatively benign environments, the yeast are studied under near-starvation conditions. This kind of severe stress may be a closer analog to what real species face in nature as populations genetically adapt to drastically altered circumstances. Inasmuch as starvation may serve as a cue to any kind of stress, from diminished resources to greatly altered temperature to an invasion by superior competitors, the results of this study should have implications for life on other planets.

    5
    Studying how life evolved on Earth could lead to a better understanding of habitability conditions in other locations, such as Mars.
    Credit: NASA/JPL

    Indeed, a major theme that runs through all of these investigations is that by studying evolutionary processes in the laboratory using simple unicellular species, we can expect to uncover rules that govern the tempo and trajectory of evolution in any population of self-replicating entities whose structure and function are programmed by information molecules.

    “What I would like fellow astrobiology researchers to be alert to is evidence of differentiation, either at the level of different proteins in a metabolic network, different genotypes in a population of a given species, different genomes in a single cell, or different cells in a multicellular organism. In each case differentiation opens the door not only to competition but also to cooperation between variants, enabling a division of labor.” he said. “We should be mindful that, however they may be encoded, lifeforms are likely to have differentiated on other worlds. Therefore, we should be alert to the signatures left by these more complex forms of life.”

    See the full article here.

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  • richardmitnick 12:59 pm on January 18, 2015 Permalink | Reply
    Tags: , Astrobiology, , Institut d'Astrophysique Spatiale   

    From Institut d’Astrophysique Spatiale: “Detection of sugars in a laboratory simulation of interstellar and pre-cometary organic matter produced from the photo/thermos chemistry of ices” 

    Institut d'Astrophysique Spatiale bloc

    Institut d’Astrophysique Spatiale

    13/01/2015
    No Writer Credit

    Ten aldehydes, including two sugars potentially important for prebiotic chemistry, have for the first time been identified in organic residues issued from photochemistry of interstellar ice analogues, produced in the laboratory by the IAS MICMOC/SUGARS experiment.

    The MICMOC experiment (Matière Interstellaire et Cométaire: Molécules Organiques Complexes) has a variant (Chiral-MICMOC on the SOLEIL synchrotron) which investigates the spatial conformation (left, L, or right D) of the amino acids produced under the photochemical action of ultraviolet circularly polarized light. The aim of this experiment is to propose an astrophysical scenario for the origin of homochirality observed in biological molecules on the Earth. The MICMOC/SUGARS experiment is another variant of the initial set-up. This fully interdisciplinary approach assembles astrophysicists, molecular physicists, and chemists. It mixes an experimental approach including a strong astrophysical background with the simulation of the evolution of interstellar ice analogues in the laboratory and sophisticated analytical chemistry methods for the detection of molecules of prebiotic interest.

    The detection of numerous amino acids in the organic residues produced by the photo/thermo-chemistry of ices has been reported, in part thanks to our collaboration between IAS (Orsay) and INC (Nice). The overall quality of the samples produced by the IAS team « Astrochimie et Origines » has been attested by the use of 13C atoms markers in the original ice samples to avoid any confusion with possible contamination of the samples during manipulation.

    Recently, a change in the analytical procedure has allowed the detection of a new family of molecules: the aldehydes. Among them are the two sugars glycolaldehyde and glyceraldehyde, potentially important for prebiotic chemistry. According to a recent study, these molecules may be considered as possible precursors of ribonucleotides (constituents of RNA), in the same manner that amino acids (which are detected within the same experimental protocol) are key molecules for the early formation of proteins. The detection of these molecules in our samples strengthens the scenario of an exogenous delivery of organic molecules essential for starting prebiotic chemistry at the surface of the early Earth.

    Finally, if glycolaldehyde is indeed detected in the interstellar medium, that is not the case yet for glyceraldehyde, which can be seen now as a potential target for large modern radioastronomy instruments such as ALMA. Glyceraldehyde could also be proposed for detection in primitive carbonaceous meteorites.

    Research paper: P. de Marcellus et al. (2015). Aldehydes and sugars from evolved precometary ice analogues: Importance of ices in astrochemical and prebiotic evolution.
    PNAS. DOI : 10.1073/pnas.1418602112 10.1073/pnas.1418602112

    2

    Left: UV source for astrochemistry experiments at IAS (picture : P. de Marcellus). Right: the “Pillars of Creation” (in the Eagle nebula) seen by the Hubble Space Telescope (HST, NASA).

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    Institut d'Astrophysique Spatiale campus

    The Institut d’Astrophysique Spatiale (IAS) is a laboratory of the National Center of Scientific Research (CNRS) and of the University of Paris-Sud 11. in addition to having the status of Observatory.The IAS comprises 140 scientists, engineers, technicians, administrators and graduate students.

     
  • richardmitnick 10:46 am on January 1, 2015 Permalink | Reply
    Tags: Astrobiology, , , , , ,   

    From SPACE.com: “Planets with Odd, Mercury-Like Orbits Could Host Life” 

    space-dot-com logo

    SPACE.com

    December 31, 2014
    Charles Choi

    Mercury has an oddball orbit — it takes longer for it to rotate on its axis and complete a day than it takes to orbit the sun and complete a year. Now, researchers suggest photosynthesis could take place on an alien planet with a similarly bizarre orbit, potentially helping support complex life.


    Orbit animation

    1
    During its first Mercury solar day (which is about 176 Earth days long) in orbit, NASA’s MESSENGER spacecraft imaged nearly the entire surface of Mercury to generate a global monochrome map at 250 meters per pixel resolution and a 1 kilometer per pixel resolution color map.
    Credit: NASA/JHU APL/CIW

    NASA Messenger satellite
    NASA/Messenger

    However, the scientists noted that the threat of prolonged periods of darkness and cold on these planets would present significant challenges to alien life, and could even potentially freeze their atmospheres. They detailed their findings in the International Journal of Astrobiology.

    Astronomers have discovered more than 1,700 alien planets in the past two decades, raising the hope that at least some might be home to extraterrestrial life. Scientists mostly focus the search for alien life on exoplanets in the habitable zones of stars. These are regions where worlds would be warm enough to have liquid water on their surfaces, a potential boon to life.

    Although many exoplanets are potentially habitable, they may differ from Earth significantly in one or more ways. For instance, habitable planets around dim red dwarf stars orbit much closer than Earth does to the sun, sometimes even closer than Mercury’s distance.

    Red dwarfs are of interest as possible habitats for life because they are the most common stars in the universe — if life can exist around red dwarfs, then life might be very common across the cosmos. Recent findings from NASA’s Kepler Space Observatory suggest that at least half of all red dwarfs host rocky planets that are one-half to four times the mass of Earth.

    NASA Kepler Telescope
    NASA/Kepler

    Since a planet in the habitable zone of a red dwarf orbits very near its star, it experiences much stronger gravitational tidal forces than Earth does from the sun, which slows the rate at which those worlds spin. The most likely result of this slowdown is that the planet enters what is technically called a 1:1 spin orbit resonance, completing one rotation on its axis every time it completes one orbit around its star.

    This rate of rotation means that one side of that planet will always face toward its star, while the other side will permanently face away, just as the moon always shows the same side to Earth. One recent study suggests that such “tidally locked” planets may develop strange lobster-shaped oceans basking in the warmth of their stars on their daysides, while the nightsides of such worlds are mostly covered in an icy shell.

    However, if a habitable red dwarf planet has a very eccentric orbit — that is, oval-shaped — it could develop what is called a 3:2 spin orbit resonance, meaning that it rotates three times for every two orbits around its star. Mercury has such an unusual orbit, which can lead to strange phenomena. For instance, at certain times on Mercury, an observer could see the sun rise about halfway and then reverse its course and set, all during the course of one mercurial day. Mercury itself is not habitable, since it lacks an atmosphere and experiences temperatures ranging from 212 to 1,292 degrees Fahrenheit (100 to 700 degrees Celsius).

    “If the sun were less intense, Mercury would be within the habitable zone, and therefore life would have to adapt to strange light cycles,” said lead study author Sarah Brown, an astrobiologist at the United Kingdom Center for Astrobiology in Edinburgh, Scotland.

    Light is crucial for photosynthesis, the process by which plants and other photosynthetic organisms use the sun’s rays to create energy-rich molecules such as sugars. Most life on Earth currently depends on photosynthesis or its byproducts in one way or the other, and while primitive life can exist without photosynthesis, it may be necessary for more complex multicellular organisms to emerge because the main source for oxygen on Earth comes from photosynthetic life, and oxygen is thought to be necessary for multicellular life to arise.

    To see what photosynthetic life might exist on a habitable red dwarf planet with an orbit similar to Mercury’s, scientists calculated the amount of light that reached all points on its surface. Their model involved a planet the same mass and diameter as the Earth with a similar atmosphere and amount of water on its surface. The red dwarf star was 30 percent the sun’s mass and 1 percent as luminous, giving it a temperature of about 5,840 degrees Fahrenheit (3,225 degrees Celsius) and a habitable zone extending from 10 to 20 percent of an astronomical unit (AU) from the star. (One AU is the average distance between Earth and the sun.)

    The scientists found that the amount of light the surface of these planets received concentrated on certain bright spots. Surprisingly, the amount of light these planets receive does not just vary over latitude as it does on Earth, where more light reaches equatorial regions than polar regions, but also varies over longitude. Were photosynthetic life to exist on worlds with these types of orbits, “one would expect to find niches that depend on longitude and latitude, rather than just latitude,” said study co-author Alexander Mead, a cosmologist at the Royal Observatory, Edinburgh, in Scotland.

    The research team found these planets could experience nights that last for months. This could pose major problems for photosynthetic life, which depends on light. Still, the scientists noted that many plants can store enough energy to last through 180 days of darkness. Moreover, some photosynthetic microbes spend up to decades dormant in the dark, while others are mixotrophic, which means they can survive on photosynthesis when light is abundant and switch to devouring food when light is absent.

    Another problem these long spans of darkness pose for life is the cold, which could freeze the atmospheres of these planets. Still, the investigators note that heat can flow from the dayside of such a planet to its nightside and prevent this freezing if that planet’s atmosphere is sufficiently dense and can trap infrared light from the planet’s star. This heat flow could lead to very strong winds, but this does not necessarily make the world uninhabitable, they added.

    “Life having to cope with such tidally driven resonances could be common in the universe,” Mead said. “It changes one’s perception of what habitable planets in the universe would be like. There are many possibilities that are very un-Earth-like.”

    However, the researchers noted that the strength of a world’s magnetic field depends in large part on how quickly it spins, which suggests that planets with orbits like Mercury’s might have relatively weak magnetic fields. This could mean these worlds are not as good at deflecting harmful electrically charged particles streaming from their red dwarfs and other stars that can damage organisms and strip off the atmospheres of these planets.

    The investigators suggested that dense atmospheres could help keep such planets habitable in the face of radiation from space. They added that life might be confined to certain spots on the surfaces of those planets that experience relatively safe levels of radiation.

    Are astronomers capable of detecting habitable planets with a 3:2 spin orbit resonance?

    “Measuring the day length of extrasolar planets is enormously difficult, and the first day length measurements for any extrasolar planets were only published this year,” Mead said. “Such a measurement for the planets we discuss would be much more difficult due to the fact that they are small, rocky planets around faint stars. This means that we are probably a long way from measuring the spin rates of such habitable worlds.”

    See the full article here.

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