... we've got company ...Signs of Life Found On Venus. Phosphine Gas On Venus Indicates That Microbes Exist There.https://webcache.googleusercontent.com/search?q=cache:dUWrpm80WHsJ:https://earthsky.org/%3Fp%3D343883+&cd=1&hl=en&ct=clnk&gl=usImage: https://preview.redd.it/wx4yza3qrum51.jpg?auto=webp&s=67a3b605fec12978a30acae05367e290682420b5Earth & Sky accidentally broke a press embargo two days early.
Scientists have detected trace amounts of the gas phosphine in the clouds of Venus, a potential indicator of life on Earth's inhospitable neighbor because on our planet this molecule is produced by microbes that inhabit oxygen-free environments.Co-author Janusz Petkowski noted:
This means either this is life, or it’s some sort of physical or chemical process that we do not expect to happen on rocky planets.
We really went through all possible pathways that could produce phosphine on a rocky planet. If this is not life, then our understanding of rocky planets is severely lacking.
PH3 gets destroyed by ultraviolet light-related chemistry, and so has a short lifetime in planetary atmospheres. This means if phosphine is detected, there must be an ongoing process generating or replenishing it.William Bains at MIT, who led the work on trying to assess other natural ways to make phosphine on Venus. Some ideas included sunlight, minerals blown upwards from the surface, volcanoes, or lightning, but none of these could make anywhere near enough of it. These kinds of sources could only make, at most, one ten thousandth of the amount of phosphine that the telescopes saw. So
something is producing a lot more of the gas. According to Paul Rimmer at Cambridge University, terrestrial organisms would only need to work at about 10% of their maximum productivity in order to produce the amount of phosphine found on Venus.
Pre-release:
Nature Astronomy, embargoed: September 14, 2020
https://www.nature.com/articles/s41550-020-1174-4https://ras.ac.uk/news-and-press/news/hints-life-venus----------------------------------------------
For 3 billion years, ending about 750 million years ago, Venus was likely hospitable, leaving the tantalizing possibility that we’ve detected the last vestiges of an ancient ecosystem.
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Phosphine Could Signal Existence of Alien Anaerobic Extraterrestrial Lifehttps://phys.org/news/2019-12-smelly-poisonous-molecule-sure-fire-extraterrestrial.ampMost life on Earth, specifically all aerobic, oxygen-breathing life, wants nothing to do with phosphine, neither producing it nor relying on it for survival.
Now MIT researchers have found that phosphine is produced by another, less abundant life form: anaerobic organisms, such as bacteria and microbes, that don't require oxygen to thrive.
The team found that phosphine cannot be produced in any other way except by these extreme, oxygen-averse organisms, making phosphine a pure biosignature—a sign of life (at least of a certain kind).In a paper recently published in the journal
Astrobiology, the researchers report that if phosphine were produced in quantities similar to methane on Earth, the gas would generate a signature pattern of light in a planet's atmosphere. This pattern would be clear enough to detect from as far as 16 light years away by a telescope such as the planned James Webb Space Telescope.
If phosphine is detected from a rocky planet, it would be an unmistakable sign of extraterrestrial life.... "It's a really toxic molecule for anything that likes oxygen. But for life that doesn't like oxygen, it seems to be a very useful molecule."Phosphine, they found, has no significant false positives, meaning any detection of phosphine is a sure sign of life. The researchers then explored whether the molecule could be detectable in an exoplanet's atmosphere. They simulated the atmospheres of idealized, oxygen-poor, terrestrial exoplanets of two types: hydrogen-rich and carbon dioxide-rich atmospheres. They fed into the simulation different rates of phosphine production and extrapolated what a given atmosphere's spectrum of light would look like given a certain rate of phosphine production. ...
Clara Sousa-Silva et al.
Phosphine as a Biosignature Gas in Exoplanet Atmospheres,
Astrobiology (2019)
https://arxiv.org/abs/1910.05224--------------------------------------------
Could There Be Life In the Cloudtops of Venus?https://phys.org/news/2020-08-life-cloudtops-venus.ampIn a paper just published in the journal Astrobiology, Sara Seager from MIT and colleagues suggest a way that microbial life could permanently reside in the lower atmosphere of Venus. The idea that microbes might exist in the Venusian clouds, at an altitude of 50 to 65 kilometers above ground level, was proposed more than 50 years ago by the late Carl Sagan, and has since been advanced by many other authors.
Previous papers didn’t elaborate on what life in the clouds means, and how it might interact with the atmosphere. A 2004 paper pointed out that sulfur (specifically a compound called cyclooctasulfur) could be used by microbes as a UV sunscreen and a means for converting ultraviolet light to other wavelengths of light that could be used for photosynthesis. It was speculated that this could be the basis for an ecosystem at Venus, where certain chemotrophic organisms complete the nutrient cycling.
Seager and her colleagues have come up with a much more elegant solution. They suggest that the droplet habitat in which the microbes reside would inexorably grow, and would be forced by gravity to settle in the hotter, uninhabitable layer below the Venusian clouds. As the droplets evaporate during settling, the microbes would dry out, and the lower haze layer would become a depot for desiccated, dormant life. But upward drafts would regularly lift the dormant microbes back into the clouds, where they would be rehydrated and become active again.
Sara Seager et al.
The Venusian Lower Atmosphere Haze as a Depot for Desiccated Microbial Life: A Proposed Life Cycle for Persistence of the Venusian Aerial Biosphere,
Astrobiology (2020)
https://www.liebertpub.com/doi/10.1089/ast.2020.2244-----------------------------------------------
Unidentified ‘Absorbers’ Soak Up Solar Energy in Upper Cloud Layer of Venushttp://www.sci-news.com/space/unidentified-absorbers-venus-07560.html... Venusian clouds contain strange, dark patches, called “unknown absorbers” because they absorb large amounts of solar radiation.No one has yet determined what these dark patches are, but scientists have speculated that they might be forms of sulfur, ferric chloride or even
microscopic life.Now, a team of scientists led by Yeon Joo Lee, a researcher in the Center for Astronomy and Astrophysics at the Technical University of Berlin, has shown that the unknown absorbers are affecting Venus’s weather
By studying more than a decade of data from Venus Express, Akatsuki, Messenger and the Hubble Space Telescope, the researchers found a relationship between Venus’ clouds and its winds. The clouds absorb solar radiation, which causes temperature changes that affect wind patterns. The unknown absorbers seem to play a role in this process by affecting the planet’s albedo, or how much energy is reflected back to space.
“It is hard to conceive of what would cause a change in the albedo without a change in the absorbers,” said Sanjay Limaye, a planetary scientist at the University of Wisconsin-Madison and paper co-author.
In part because it is difficult to explain the absorbers’ changes inorganically, Limaye has explored the possibility that they might be microorganisms. He’s in good company. The idea of life in the Venusian atmosphere dates back to a 1967 paper co-authored by Carl Sagan.
Limaye observed that the particles making up the dark patches in Venus’s clouds resemble microorganisms in Earth’s atmosphere. “Since there are few species which have physical, chemical and spectral properties that are consistent with the composition of the Venus clouds, they may have evolved independently on Venus.”
Yeon Joo Lee et al. . Long-term Variations of Venus’s 365 nm Albedo Observed by Venus Express, Akatsuki, MESSENGER, and the Hubble Space Telescope[/b], Astronomical Journal, 2019
https://iopscience.iop.org/article/10.3847/1538-3881/ab3120