26 September 2020 | New Scientist | 21I
F MARS were the popular kid
in school, Venus would be
the nerd sitting in the corner,
largely ignored. Despite its image,
Venus is the brightest object in the
sky after the sun and the moon,
its orbit taking it closer to Earth
than any other planet in the solar
system. It has nearly the same
mass and size as Earth, but being
closer to our star, it gets nearly
twice as much heat from the sun.
However, instead of having
a climate that is just a warmer
version of Earth’s, Venus’s surface
and atmosphere are hellish:
clouds of sulphuric acid blanket
the planet, while at ground level
it is hot enough to melt lead.
Despite this, there is now a sign
that Venus may harbour life.
Jane Greaves at Cardiff
University, UK, and her colleagues
recently detected phosphine in
Venus’s atmosphere, with one
potential explanation that it is
the by-product of biology. That is
because the only way this gas is
made on Earth is in laboratories or
by microbes. Though this doesn’t
mean it was produced by life
on Venus, attempts to find non-
biological explanations for its
presence have so far fallen short.
Our best hope for confirming or
rejecting the possibility of life on
Venus is to go and have a proper
look. During the cold war, the USSR
sent more than a dozen missions
to Venus, including several landers
and a pair of balloons, but these
ended well before the dawn of the
1990s. Likewise, NASA hasn’t
MIlaunched a mission dedicated to
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cryogenics p30Venus since the late 1980s. What’s
more, no US mission has plumbed
the depths of its atmosphere and
probed its surface since the
Pioneer Venus missions that
departed Earth in the 1970s.
Other countries have had more
recent efforts: the European Space
Agency’s Venus Express orbited
the planet throughout the late
2000s and early 2010s, while
Japan’s Akatsuki orbiter is
exploring Venus right now. But
these missions were ill-equipped
for detecting phosphine or life.
While Mars has been the focus
of interplanetary exploration
efforts of late, with some spaceagencies focusing on landing
more craft and even people on its
surface, the phosphine discovery
has people looking at Venus in a
new light. As NASA administrator
Jim Bridenstine tweeted: “It’s
time to prioritize Venus.”
In the months and years to
come, computer simulations
will be used to further study
the possible chemistries of the
atmosphere on Venus. More
observations will be made (and
the old ones reanalysed) and
laboratory experiments will be
conducted to try to identify other
ways the phosphine there could
be produced. However, there is noguarantee that these efforts will
reveal the true nature of this
substance on Venus.
A new mission to directly
sample the atmosphere and
surface would be a watershed
moment in planetary science. It
need not only look for signs of life,
but also answer some of our many
questions about Venus, such as
why it became so different to Earth
and whether it was once habitable.
Some options to do this
already exist. There are two
NASA missions currently vying
for approval, India aims to send
an orbiter to Venus in 2023 and
private company RocketLab also
has plans to visit in that year,
hopefully with a probe passing
through the planet’s atmosphere.
By sampling the chemistry
in the Venusian air, we would be
able to take direct measurements
of phosphine and see how it varies
with height, capture any other
chemicals that contribute to its
formation and potentially detect
any life that may be there.
The discovery of phosphine
in Venus’s atmosphere is a great
accomplishment. The scientific
endeavour it has set in motion is
as if a sleeping giant has awakened
and it may be just what we need to
finally refocus on this neglected
world. The quiet kid in the corner
may yet get the last laugh. ❚Let’s get back to Venus
Phosphine in Venus’s atmosphere could be a sign that life is there.
The only way to find out for sure is to go have a look, writes Peter GaoPeter Gao is a Sagan
Postdoctoral Fellow at the
University of California,
Santa Cruz