Venus is the most similar planet to the Earth in size and position, but its atmosphere is very different. To help shed light on why, a group of scientists have - for the first time - made direct observations of atomic oxygen on both the day and night sides of the second planet from the Sun.

Using data from upGREAT array spectrometer on board the Stratospheric Observatory for Infrared Astronomy (SOFIA) airplane - NASA's modified Boeing 747SP aircraft carrying a 2.7-meter (106-inch) reflecting telescope - a research team based in Germany detected atomic oxygen at all observed points and found it to be concentrated at altitudes of around 100km.

Until the upGREAT observations, it had only been observed by proxy on the night side of Venus - via a faint emission of light by the atmosphere.

A day on Venus lasts 243 Earth days, which is longer than its year of about 225 Earth days - yep, it takes Venus longer to rotate once on its own axis than it takes the planet to complete one orbit of the Sun. Earth's neighbor has a thick carbon dioxide atmosphere, and continuous sulfuric acid cloud cover creates extreme greenhouse effects and contributes to an inhospitable surface temperature of 464°C (867˚F).

Atomic oxygen (O₁) is a very reactive allotrope of the element that isn't very common on Earth's surface (but abundant farther out, in Low Earth Orbit) and is expected to become important in understanding the atmospheric processes on Venus. O₁ is produced on the day side of Venus by the breakdown of CO₂ (carbon dioxide) and CO (carbon monoxide), after which it is transported to the night side.

The observations were made by a research team led by Heinz-Wilhelm Hübers, a professor at Germany's Deutsches Zentrum für Luft-und Raumfahrt (DLR), a center for aerospace research in Berlin, with the research set to support future space missions to Venus. Direct measurements of atomic oxygen may also support scientific understanding of why Venus's atmosphere is so different to that of Earth, according to the study, published this week in Nature Communications.

"The atomic oxygen is concentrated at altitudes around 100km with a maximum column density on the day side where it is generated by photolysis of carbon dioxide and carbon monoxide. This method enables detailed investigations of the Venusian atmosphere in the region between the two atmospheric circulation patterns in support of future space missions to Venus," it said.

The authors wrote that future observations will provide a more detailed picture of the atmosphere and support future space missions to Venus - such as NASA's DaVinci (Deep Atmosphere Venus Investigation of Noble gases, Chemistry, and Imaging) mission as well as the EnVision mission of the European Space Agency.

"Along with measurements of atomic oxygen in the atmospheres of Earth and Mars, these data may help to improve our understanding of how and why Venus and Earth atmospheres are so different," the paper noted. ®

https://www.theregister.com//2023/11/08/venus_oxygen_measures_to_help/