Myself, I’m a big fan of exploring the ice worlds of our solar system. And there is a lot cooking on that front. (e.g., this, this, this, this, this, this, this)
But on the opposite end of the spectrum, there is new interest in Venus, a very non-icy planet. Earlier expeditions were able to just barely land and survived on the surface for less than a day before being boiled/crushed/dissolved by acid. Venus is harsh.
Venus also appears to have been pretty similar to Earth, but experienced “runaway greenhouse warming” some time in the past. As such, it could be an interesting case that sheds light on the Earth’s future climate in the likely event that the primate infestation continues unabated.
Interest also has turned to the deep and complicated atmosphere of Venus, which could be explored by airships and floating cities! Yes! A more conventional mission is planned for 2030+ [3].
Part of the excitement stems from the complicated and energetic chemistry in the clouds, which might support some kind of life. To date, we have sparse remote observations, so sampling (with or without floating cities) would really help clarify things.
Because the big problem with remote sensing is that it is highly uncertain and difficult to interpret in the absence of ground (or cloud) truth as a foundation.
For example, there has been a lot of excitement about observations of phosphine in the clouds of Venus which, on Earth, is generally produced by microbial life. So that’s suggestive, though it’s really hard to build the rest of the case for life, since we don’t know where the phosphine is, or what else is going on.
This summer researchers from Belfast and elsewhere report a study of the water activity in the atmosphere of Venus, based on various remote sensed data [2]. Their conclusion is not that surprising: the clouds of Venus are dry. Really, really dry.
This conclusion is based on theoretical calculations using observed humidity (i.e., water) and the estimated sulfuric acid droplets. This yields an estimate of “water activity”, which is crucial for any water-based biochemical activity. This technique can be applied elsewhere, e.g., Jupiter or even exoplanets.
Assuming this analysis is correct, this means that life as we know it on Earth would not be able to live there.
Given the extremely unearthly environment on Venus, I think it’s a safe bet that there isn’t Earth-like life there. There could be really strange life, of course. And that would be supercool to know about. But I wouldn’t waste a lot of effort looking for close cousins living on Venus. If there is life related to us, it’s going to be on the ice worlds.
What about the phosphine? Who knows. We may well discover previously unknown chemistry that can generate phosphine that has nothing to do with microbes.
So, the proposed missions to Venus will learn a lot, and possibly help us understand the runaway greenhouse phenomenon we are pushing towards. We might discover exotic chemistry and even really exotic lifeforms. But we ain’t going to find Earth-like life.
- Jonathan Amos, Clouds of Venus ‘simply too dry’ to support life, in BBC News – Science & Environment, June 29, 2021. https://www.bbc.com/news/science-environment-57641247
- John E. Hallsworth, Thomas Koop, Tiffany D. Dallas, María-Paz Zorzano, Juergen Burkhardt, Olga V. Golyshina, Javier Martín-Torres, Marcus K. Dymond, Philip Ball, and Christopher P. McKay, Water activity in Venus’s uninhabitable clouds and other planetary atmospheres. Nature Astronomy, 2021/06/28 2021. https://doi.org/10.1038/s41550-021-01391-3
- William Steigerwald and Nancy Neal Jones, NASA to Explore Divergent Fate of Earth’s Mysterious Twin with Goddard’s DAVINCI+, in NASA’s Goddard Space Flight Center – Latest, June 2, 2021. https://www.nasa.gov/feature/goddard/2021/nasa-to-explore-divergent-fate-of-earth-s-mysterious-twin-with-goddard-s-davinci
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