Breakfast at Exo-Tiffany’s

A couple of weeks ago, on September 14th, an international team of astronomers reported they have spotted signs of phosphine (PH3) in Venus’s atmosphere(1), in observations from the James Clerk Maxwell Telescope (JCMT), and the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile, a more sensitive telescope.

Phosphine can be produced by microbes on the Earth, and it is therefore considered a potential biomarker of extra-terrestrial life. Researchers examined potential non-biological sources such as volcanism, meteorites, lightning and various types of chemical reactions. Phosphine has been detected, for example, in the atmospheres of Jupiter and Saturn. The molecule is formed deep inside the giant planets and transported to the upper layers by atmospheric circulation. However, Venus is a rocky planet so that a similar chemistry cannot be used to produce phosphine.

Does it mean we have found life in Venus? It’s too soon to say. “Fortunately, Venus is right next door, so we can literally go and check.” and that’s what NASA seems to be re-considering

Confirming the existence of (what we call) life in another planet is an exciting prospect, particularly if it is one of the planets of our Solar System. By the way, that would mean we are not so special, and given how we are, the beginning of another tough Galilean debate.

That’s why I want to draw your attention to another scientific announcement this month. In a new study(2) published in The Planetary Science Journal, a team of researchers from Arizona State University (ASU) and the University of Chicago have determined that some carbon-rich exoplanets, given the right circumstances, could be made of diamonds and silica.

Fig. 4 op. cit.

Carbon-rich planets likely do not have the properties needed for (what we call) life. “These exoplanets are unlike anything in our solar system,” says lead author Harrison Allen-Sutter of ASU’s School of Earth and Space Exploration. But who cares? First, think carefully: if you could choose (you couldn’t, of course) what would you prefer? A universe teeming with life or a universe full of diamonds? Second, and more interestingly. The truth is we do not have the slightest idea of what life is.

Life is one of those ideas that when we try to isolate it, like a virus, completely evades our comprehension skills. To the best of my knowledge, there are more than one hundred potential definitions(3). Lately it has become unpopular to talk about definitions of life(4), under the assumption that attempts at a precise definition are counterproductive. However, like Philip Ball remarks, (paraphrasing Lewis Carol), you can’t hunt for something if you have no idea what it is’.

So, just for the pleasure of drifting, off to imagine the world, let me think of a delightful Audrey Hepburn made out of diamonds, waiting for me in one of those remote carbon-rich exoplanets

There’s such a lot of world to see!


(1) Greaves, J.S., Richards, A.M.S., Bains, W., Rimmer, P.B., Sagawa, H., Clements, D.L., Seager, S., Petkowski, J.J., Sousa-Silva, C., Ranjan, S., et al. (2020). Phosphine gas in the cloud decks of Venus. Nature Astronomy 1–10.

(2) Allen-Sutter, H., Garhart, E., Leinenweber, K., Prakapenka, V., Greenberg, E., and Shim, S.-H. (2020). Oxidation of the Interiors of Carbide Exoplanets. Planet. Sci. J. 1, 39.

(3) Trifonov, E.N. (2011). Vocabulary of definitions of life suggests a definition. Journal of Biomolecular Structure and Dynamics 29, 259–266.

(4) Mix, L.J. (2014). Defending Definitions of Life. Astrobiology 15, 15–19.

Featured Image: Audrey Hepburn in “Breakfast at Tiffany’s.”Paramount Pictures (with a pinch of diamonds 😉

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