If Mars were the popular kid in school, Venus would be the weird 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 experiences nearly twice as much heating from the sun.
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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 and the pressure is 100 times that at sea level on our world. Despite this, there is now a sign that Venus may harbour life.
Jane Greaves at Cardiff University, UK, and colleagues recently detected phosphine in Venus’s atmosphere, with one potential explanation that it is the by-product of biology. Though this doesn’t mean it was produced by life, attempts to find non-biological explanations for the presence of this gas have so far fallen short. Our best hope for either confirming or rejecting the possibility of Venusian life is to go and have a proper look.
During the Soviet era, Russia 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 launched a mission dedicated to Venus since the late 1980s, when the Magellan orbiter lifted off. 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 late 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. However, these missions were ill-equipped for detecting phosphine or life.
While Mars has been the focus of a lot of interplanetary exploration efforts of late, with some space agencies 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 re-analysed) and laboratory experiments will be conducted to try to identify other ways the phosphine there could be produced. However, there is no guarantee that these efforts will reveal the true nature of this substance on Venus.
A new mission to directly sample the atmosphere and surface of Venus 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 evolved so differently from Earth? And whether it was once habitable.
Some options to do this already exist. There are two NASA missions currently vying for approval, India plans 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 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 that 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.
Peter Gao is a Sagan Postdoctoral Fellow at the university of California, Santa Cruz
