(ORDO NEWS) — Due to the lack of direct observations of extraterrestrial life, scientists often focus on looking for the chemical by-products of life that can be detected using remote sensing.
In 2021, planetary astronomers reported the discovery of phosphine in the atmosphere of Venus during ground-based observations.
The concentration of the gas was reported to be 20 ppb, but this was later revised to 7 ppb or less.
On Earth, phosphine can be associated with biological processes, and researchers are studying whether this gas could be a sign of life on other planets.
The alleged discovery of phosphine has been met with skepticism due to difficulties in calibrating and analyzing ground-based observational data.
Subsequent attempts to detect phosphine in the atmosphere of Venus using other ground-based and space telescopes also failed.
Then the researchers were given another set of measurements from a unique observational platform: the Stratospheric Observatory for Infrared Astronomy (SOFIA).
The SOFIA aircraft flies at an altitude of 13 kilometers, which greatly reduces the contamination of the phosphine signal from ground sources.
The researchers used the German GREAT instrument, which has very high spectral resolution, to collect far-infrared spectroscopic data from 75 to 110 kilometers above the surface of Venus, very close to the altitude range measured in the previous study.
The researchers report that data collected by GREAT during three observation flights revealed no clear signs of phosphine.
If any phosphine is present in Venus’s atmosphere, and assuming the amount is constant over time, the new observations point to an upper limit of 0.8 parts per billion.
This level is the most stringent upper limit presented to date for the entire Earth-facing hemisphere of Venus.
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