Back in 2020, astronomers searching for extra-terrestrial life got excited when Japan’s Venus-orbiting satellite Akatsuki detected phosphine in the planet’s atmosphere.
This was significant as the compound is considered to be a potential sign of life. It is unlikely to arise from chemical processes that occur on rocky worlds such as Venus but it is known to be produced by microbial organisms in bogs, swamps, and marshes on Earth.
“Phosphine is a relatively simple chemical compound — it’s just a phosphorus atom with three hydrogens — so you would think that would be fairly easy to produce. But on Venus, it’s not obvious how it could be made,” said Dr Martin Cordiner, a researcher in astrochemistry and planetary science at NASA’s Goddard Space Flight Center, Maryland.
Now, an analysis of data collected by NASA’s Stratospheric Observatory for Infrared Astronomy (SOFIA) has turned up no evidence of phosphine in Venus's whatsoever, suggesting the Akatsuki study was flawed.
SOFIA was a telescope mounted on a Boeing 474 that was recently retired from service. It was positioned in orbit around 13,000m from the Earth's surface in the stratosphere, putting it above 99 per cent of the atmosphere’s infrared-blocking effects. This allowed astronomers to study the Solar System in ways not possible with ground-based telescopes.
The data analysed in the study were collected during observations of Venus’s atmosphere over the course of three flights carried out in November 2021. SOFIA’s telescope’s high resolution enabled it to scan for traces of phosphine around 75 to 110km above the entirety of the planet’s surface – the same region as the original 2020 finding. However, no sign of the compound was found.
The findings complement data taken from other experiments carried out since 2020 that all point to phosphine not existing anywhere in Venus’s atmosphere, from the equator to the poles.
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