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| Possible NASA Havoc Mission to Venus |
Recently, there was some very exciting news about possible biosignatures in an unexpected place within our Solar System. Amazingly, it was announced this month by Greaves et al. 2020 that Phosphine gas was detected in the cloud decks of Venus. What is so striking about this is that the levels of Phosphine measured do not match any known abiotic terrestrial mechanism, or, as the authors stated - "The presence of PH3 is unexplained after exhaustive study of steady-state chemistry and photochemical pathways, with no currently known abiotic production routes in Venus’s atmosphere, clouds, surface and subsurface, or from lightning, volcanic or meteoritic delivery."
Phosphine (PH3), a toxic gas, is commonly created by organic life typically deep in bogs and swamps (see Devai & Delaune 1995) as well as by microbial metabolism (see Glindemann et al. 2005). Though it can be created by other abiotic means, the levels were significantly lower than what was calculated from sunlight, meteorites, lightning or emissions from volcanism on Venus' surface. Even degassing from Venus' mantle rocks is about 10 orders of magnitude too low to produce PH3.
It should be noted that the announcement is by no means a confirmation of a biosignature. The team clearly calls this out - Venus' surface composition, temperature and atmospheric interaction stills needs additional data. "This could be unknown photochemistry or geochemistry, or possibly life. Information is lacking—as an example, the photochemistry of Venusian cloud droplets is almost completely unknown. Hence a possible droplet-phase photochemical source for PH3 must be considered (even though PH3 is oxidized by sulfuric acid). Questions of why hypothetical organisms on Venus might make PH3 are also highly speculative". Interestingly, phosphine is also found in Jupiter's atmosphere thought to be caused by abiotic turbulent atmospheric mixing.
This is quite a remarkable discovery considering Venus' proximity and number of observations from both Earth and space observatories and probes which should spur a significant amount of funding for future Venus missions.
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