Possible marker of life spotted on venus

Date:
September 14, 2020
Source:
ESO
Summary:
Astronomers have discovered a rare molecule -- phosphine -- in the
clouds of Venus. On Earth, this gas is only made industrially or
by microbes that thrive in oxygen-free environments. Astronomers
have speculated for decades that high clouds on Venus could offer
a home for microbes - - floating free of the scorching surface but
needing to tolerate very high acidity. The detection of phosphine
could point to such extra- terrestrial 'aerial' life.



FULL STORY ========================================================================== [Planet Venus (stock | Credit: (c) Igor_Filonenko / stock.adobe.com]
Planet Venus (stock image; elements furnished by NASA).

Credit: (c) Igor_Filonenko / stock.adobe.com [Planet Venus (stock |
Credit: (c) Igor_Filonenko / stock.adobe.com] Planet Venus (stock image; elements furnished by NASA).

Credit: (c) Igor_Filonenko / stock.adobe.com Close An international
team of astronomers today announced the discovery of a rare molecule -- phosphine -- in the clouds of Venus. On Earth, this gas is only made industrially or by microbes that thrive in oxygen-free environments.

Astronomers have speculated for decades that high clouds on Venus could
offer a home for microbes -- floating free of the scorching surface but
needing to tolerate very high acidity. The detection of phosphine could
point to such extra-terrestrial 'aerial' life.


========================================================================== "When we got the first hints of phosphine in Venus's spectrum, it was
a shock!," says team leader Jane Greaves of Cardiff University in the
UK, who first spotted signs of phosphine in observations from the James
Clerk Maxwell Telescope (JCMT), operated by the East Asian Observatory,
in Hawai'i.

Confirming their discovery required using 45 antennas of the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile, a more sensitive telescope
in which the European Southern Observatory (ESO) is a partner. Both
facilities observed Venus at a wavelength of about 1 millimetre, much
longer than the human eye can see -- only telescopes at high altitude
can detect it effectively.

The international team, which includes researchers from the UK, US and
Japan, estimates that phosphine exists in Venus's clouds at a small concentration, only about twenty molecules in every billion. Following
their observations, they ran calculations to see whether these amounts
could come from natural non- biological processes on the planet. 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 non-biological sources were found to make at most
one ten thousandth of the amount of phosphine that the telescopes saw.

To create the observed quantity of phosphine (which consists of hydrogen
and phosphorus) on Venus, terrestrial organisms would only need to work
at about 10% of their maximum productivity, according to the team. Earth bacteria are known to make phosphine: they take up phosphate from minerals
or biological material, add hydrogen, and ultimately expel phosphine. Any organisms on Venus will probably be very different to their Earth cousins,
but they too could be the source of phosphine in the atmosphere.

While the discovery of phosphine in Venus's clouds came as a surprise,
the researchers are confident in their detection. "To our great relief,
the conditions were good at ALMA for follow-up observations while
Venus was at a suitable angle to Earth. Processing the data was tricky,
though, as ALMA isn't usually looking for very subtle effects in very
bright objects like Venus," says team member Anita Richards of the UK
ALMA Regional Centre and the University of Manchester. "In the end, we
found that both observatories had seen the same thing -- faint absorption
at the right wavelength to be phosphine gas, where the molecules are
backlit by the warmer clouds below," adds Greaves, who led the study
published today in Nature Astronomy.

Another team member, Clara Sousa Silva of the Massachusetts Institute
of Technology in the US, has investigated phosphine as a "biosignature"
gas of non-oxygen-using life on planets around other stars, because
normal chemistry makes so little of it. She comments: "Finding phosphine
on Venus was an unexpected bonus! The discovery raises many questions,
such as how any organisms could survive. On Earth, some microbes can
cope with up to about 5% of acid in their environment -- but the clouds
of Venus are almost entirely made of acid." The team believes their
discovery is significant because they can rule out many alternative ways
to make phosphine, but they acknowledge that confirming the presence of
"life" needs a lot more work. Although the high clouds of Venus have temperatures up to a pleasant 30 degrees Celsius, they are incredibly
acidic -- around 90% sulphuric acid -- posing major issues for any
microbes trying to survive there.

ESO astronomer and ALMA European Operations Manager Leonardo Testi,
who did not participate in the new study, says: "The non-biological
production of phosphine on Venus is excluded by our current understanding
of phosphine chemistry in rocky planets' atmospheres. Confirming the
existence of life on Venus's atmosphere would be a major breakthrough for astrobiology; thus, it is essential to follow-up on this exciting result
with theoretical and observational studies to exclude the possibility that phosphine on rocky planets may also have a chemical origin different
than on Earth." More observations of Venus and of rocky planets
outside our Solar System, including with ESO's forthcoming Extremely
Large Telescope, may help gather clues on how phosphine can originate
on them and contribute to the search for signs of life beyond Earth.

This research was presented in the paper "Phosphine Gas in the Cloud
Decks of Venus" to appear in Nature Astronomy.

The team is composed of Jane S. Greaves (School of Physics & Astronomy,
Cardiff University, UK [Cardiff]), Anita M. S. Richards (Jodrell Bank
Centre for Astrophysics, The University of Manchester, UK), William Bains (Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, USA [MIT]), Paul Rimmer (Department of Earth
Sciences and Cavendish Astrophysics, University of Cambridge and MRC
Laboratory of Molecular Biology, Cambridge, UK), Hideo Sagawa (Department
of Astrophysics and Atmospheric Science, Kyoto Sangyo University, Japan),
David L. Clements (Department of Physics, Imperial College London, UK [Imperial]), Sara Seager (MIT), Janusz J.

Petkowski (MIT), Clara Sousa-Silva (MIT), Sukrit Ranjan (MIT), Emily
Drabek- Maunder (Cardiff and Royal Observatory Greenwich, London, UK),
Helen J. Fraser (School of Physical Sciences, The Open University,
Milton Keynes, UK), Annabel Cartwright (Cardiff), Ingo Mueller-Wodarg (Imperial), Zhuchang Zhan (MIT), Per Friberg (EAO/JCMT), Iain Coulson (EAO/JCMT), E'lisa Lee (EAO/JCMT) and Jim Hoge (EAO/JCMT).

An accompanying paper by some of team members, titled "The Venusian Lower Atmosphere Haze as a Depot for Desiccated Microbial Life: A Proposed Life
Cycle for Persistence of the Venusian Aerial Biosphere," was published in Astrobiology in August 2020. Another related study by some of the same
authors, "Phosphine as a Biosignature Gas in Exoplanet Atmospheres,"
was published in Astrobiology in January 2020.


========================================================================== Story Source: Materials provided by ESO. Note: Content may be edited
for style and length.


========================================================================== Journal References:
1. Jane S. Greaves, Anita M. S. Richards, William Bains, Paul
B. Rimmer,
Hideo Sagawa, David L. Clements, Sara Seager, Janusz J. Petkowski,
Clara Sousa-Silva, Sukrit Ranjan, Emily Drabek-Maunder, Helen
J. Fraser, Annabel Cartwright, Ingo Mueller-Wodarg, Zhuchang Zhan,
Per Friberg, Iain Coulson, E'lisa Lee, Jim Hoge. Phosphine gas in
the cloud decks of Venus.

Nature Astronomy, Sept. 14, 2020; DOI: 10.1038/s41550-020-1174-4
2. Sara Seager, Janusz J. Petkowski, Peter Gao, William Bains,
Noelle C.

Bryan, Sukrit Ranjan, Jane Greaves. 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; DOI: 10.1089/ast.2020.2244
3. Clara Sousa-Silva, Sara Seager, Sukrit Ranjan, Janusz Jurand
Petkowski,
Zhuchang Zhan, Renyu Hu, William Bains. Phosphine as a Biosignature
Gas in Exoplanet Atmospheres. Astrobiology, 2020; 20 (2): 235 DOI:
10.1089/ ast.2018.1954 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/09/200914112219.htm

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