Thread by @DrFunkySpoon

Several folks have asked me what I think about this new paper in Nature claiming that the clouds of Venus have been shown to be “uninhabitable” because of the very low water activity: tinyurl.com/3k4d7tuf
So a short thread about it:
1/

The work is solid in that the calculations (of water activity as a function of sulfuric acid concentration) seem to have been done correctly. However, the conclusions of the paper are overconfident because we know less about both the atmosphere of Venus, 2/

and about the nature of life, than the authors pretend.

They also somewhat misrepresent the state of the field.
The second sentence of the abstract is not true. It says that discussions of possible habitability of the Venus clouds “usually neglect the role of water activity”. 3

Actually many papers, including that I am co-author of, mention water activity as being a crucial factor.

In reading this paper you would think it is established fact that the cloud decks of Venus are known to be pure sulfuric acid
4/

and that the H2SO4 content at every altitude is known to within 1/10 of a weight percent.
This is wildly overconfident. In reality there are many huge mysteries of cloud composition, many hints that the cloud decks are not uniform and homogeneous,
5/

and many suggestions that the large particles are not pure H2SO4, and contain other unknown substances, and some big mysteries of atmospheric composition that are more easily answered if not all of the particles are pure sulfuric acid.
6/

Thus table 1 of the paper gives a false impression of what is solidly established about the clouds.
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The authors can be forgiven for their other area of overconfidence, in claiming to know the limits of life in the universe and what makes a place “uninhabitable” based on the observed limits of terrestrial life. This is a common practice in astrobiology
8/

and we won’t know if it is wise or foolish until we discover some other examples of life. However, if you do a search of their paper for the phrase “we believe” you will see that the overconfident statement of the clouds being “uninhabitable” in the paper title is actually
9/

, in the fine print, attributed to the author’s opinions about the nature of life.

Thus, as I said, the calculations are solid but the context is somewhat misrepresented and the conclusions are not as solid as would appear to the casual reader.
10/

There remain many reasons to believe that life in the Venus clouds is plausible and we won’t know more until we better characterize the environment with new missions. Fortunately we are going to have several chances to do so in the coming years, so stay tuned!
11/11

12/11

Here’s an older thread in which I discuss the case for life in the clouds:

threadreaderapp.com/thread/1305519…