Could acid-neutralizing life-forms make habitable pockets in Venus'
clouds?
A new study shows it's theoretically possible. The hypothesis could be
tested soon with proposed Venus-bound missions.

Date:
December 20, 2021
Source:
Massachusetts Institute of Technology
Summary:
A new study supports the longstanding idea that if life exists, it
might make a home in Venus' clouds. The study's authors identified
a chemical pathway by which life could neutralize Venus' acidic
environment, creating a self-sustaining, habitable pocket in
the clouds.



FULL STORY ==========================================================================
It's hard to imagine a more inhospitable world than our closest planetary neighbor. With an atmosphere thick with carbon dioxide, and a surface
hot enough to melt lead, Venus is a scorched and suffocating wasteland
where life as we know it could not survive. The planet's clouds are
similarly hostile, blanketing the planet in droplets of sulfuric acid
caustic enough to burn a hole through human skin.


==========================================================================
And yet, a new study supports the longstanding idea that if life exists,
it might make a home in Venus' clouds. The study's authors, from MIT,
Cardiff University, and Cambridge University, have identified a chemical pathway by which life could neutralize Venus' acidic environment,
creating a self- sustaining, habitable pocket in the clouds.

Within Venus' atmosphere, scientists have long observed puzzling
anomalies - - chemical signatures that are hard to explain, such as
small concentrations of oxygen and nonspherical particles unlike sulfuric acid's round droplets.

Perhaps most puzzling is the presence of ammonia, a gas that was
tentatively detected in the 1970s, and that by all accounts should not
be produced through any chemical process known on Venus.

In their new study, the researchers modeled a set of chemical processes to
show that if ammonia is indeed present, the gas would set off a cascade
of chemical reactions that would neutralize surrounding droplets of
sulfuric acid and could also explain most of the anomalies observed in
Venus' clouds. As for the source of ammonia itself, the authors propose
that the most plausible explanation is of biological origin, rather than
a nonbiological source such as lightning or volcanic eruptions.

As they write in their study, the chemistry suggests that "life could be
making its own environment on Venus." This tantalizing new hypothesis
is testable, and the researchers provide a list of chemical signatures
for future missions to measure in Venus' clouds, to either confirm or contradict their idea.



==========================================================================
"No life that we know of could survive in the Venus droplets," says
study co- author Sara Seager, the Class of 1941 Professor of Planetary
Sciences in MIT's Department of Earth, Atmospheric and Planetary Sciences (EAPS). "But the point is, maybe some life is there, and is modifying
its environment so that it is livable." The study's co-authors include
Janusz Petkowski, William Bains, and Paul Rimmer, who are affiliated
with MIT, Cardiff University, and Cambridge University.

Life suspect "Life on Venus" was a trending phrase last year, when
scientists including Seager and her co-authors reported the detection
of phosphine in the planet's clouds. On Earth, phosphine is a gas that
is produced mainly through biological interactions. The discovery of
phosphine on Venus leaves room for the possibility of life. Since then, however, the discovery has been widely contested.

"The phosphine detection ended up becoming incredibly controversial,"
Seager says. "But phosphine was like a gateway, and there's been this resurgence in people studying Venus." Inspired to look more closely,
Rimmer began combing through data from past missions to Venus. In these
data, he identified anomalies, or chemical signatures, in the clouds
that had gone unexplained for decades. In addition to the presence of
oxygen and nonspherical particles, anomalies included unexpected levels
of water vapor and sulfur dioxide.



========================================================================== Rimmer proposed the anomalies might be explained by dust. He argued
that minerals, swept up from Venus' surface and into the clouds,
could interact with sulfuric acid to produce some, though not all, of
the observed anomalies. He showed the chemistry checked out, but the
physical requirements were unfeasible: A massive amount of dust would
have to loft into the clouds to produce the observed anomalies.

Seager and her colleagues wondered if the anomalies could be explained by ammonia. In the 1970s, the gas was tentatively detected in the planet's
clouds by the Venera 8 and Pioneer Venus probes. The presence of ammonia,
or NH3,was an unsolved mystery.

"Ammonia shouldn't be on Venus," Seager says. "It has hydrogen attached to
it, and there's very little hydrogen around. Any gas that doesn't belong
in the context of its environment is automatically suspicious for being
made by life." Livable clouds If the team were to assume that life was
the source of ammonia, could this explain the other anomalies in Venus'
clouds? The researchers modeled a series of chemical processes in search
of an answer.

They found that if life were producing ammonia in the most efficient
way possible, the associated chemical reactions would naturally yield
oxygen. Once present in the clouds, ammonia would dissolve in droplets
of sulfuric acid, effectively neutralizing the acid to make the droplets relatively habitable.

The introduction of ammonia into the droplets would transform their
formerly round, liquid shape into more of a nonspherical, salt-like
slurry. Once ammonia dissolved in sulfuric acid, the reaction would
trigger any surrounding sulfur dioxide to dissolve as well.

The presence of ammonia then could indeed explain most of the major
anomalies seen in Venus' clouds. The researchers also show that sources
such as lightning, volcanic eruptions, and even a meteorite strike could
not chemically produce the amount of ammonia required to explain the
anomalies. Life, however, might.

In fact, the team notes that there are life-forms on Earth -- particuarly
in our own stomachs -- that produce ammonia to neutralize and make
livable an otherwise highly acidic environment.

"There are very acidic environments on Earth where life does live, but
it's nothing like the environment on Venus -- unless life is neutralizing
some of those droplets," Seager says.

Scientists may have a chance to check for the presence of ammonia,
and signs of life, in the next several years with the Venus Life Finder Missions, a set of proposed privately funded missions, of which Seager
is principal investigator, that plan to send spacecraft to Venus to
measure its clouds for ammonia and other signatures of life.

"Venus has lingering, unexplained atmospheric anomalies that are
incredible," Seager says. "It leaves room for the possibility of life."
This research was supported in part by the Simons Foundation, the Change Happens Foundation, and the Breakthrough Initiatives.

========================================================================== Story Source: Materials provided by
Massachusetts_Institute_of_Technology. Original written by Jennifer
Chu. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. William Bains, Janusz J. Petkowski, Paul B. Rimmer, Sara Seager.

Production of ammonia makes Venusian clouds habitable and explains
observed cloud-level chemical anomalies. Proceedings of the
National Academy of Sciences, 2021; 118 (52): e2110889118 DOI:
10.1073/ pnas.2110889118 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/12/211220190650.htm

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