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WASHINGTON — Oxygen makes up about 21 percent of Earth’s air, with the rest of our atmosphere made up mostly of nitrogen. And most living things – including humans, as we well know – need oxygen to survive.
Earth’s planetary neighbor, Venus, offers an entirely different story. Its thick, noxious atmosphere is dominated by carbon dioxide — 96.5 percent — with lesser amounts of nitrogen and trace gases. Oxygen is almost absent. In fact, because Venus receives far less scientific attention than other planets like Mars, direct detection of its oxygen remains difficult.
Using an instrument aboard the SOFIA airborne observatory – a Boeing 747SP aircraft modified to carry an infrared telescope as part of a joint project between NASA and the German Aerospace Center – scientists have now detected atomic oxygen in a thin layer sandwiched between two other layers of the Venusian atmosphere. .
They noted that this atomic oxygen, consisting of a single oxygen atom, differs from molecular oxygen, consisting of two oxygen atoms and breathing.
Researchers have detected oxygen for the first time directly on the sun-facing side of Venus – where it is actually produced in the atmosphere – as well as on the side facing away from the sun, where it had previously been spotted by a terrestrial probe. telescope based in Hawaii. Venus rotates much more slowly than Earth.
“The atmosphere of Venus is very dense. Its composition is also very different from that of Earth,” said German Aerospace Center physicist Heinz-Wilhelm Hübers, lead author of the study published in the journal Nature Communications.
The thick atmosphere of the second planet from the Sun traps heat in an uncontrollable greenhouse effect.
“Venus is not hospitable, at least for the organisms we know about on Earth,” Hübers added.
Oxygen is produced on the dayside of the planet by ultraviolet radiation from the sun, which breaks down atmospheric carbon dioxide and carbon monoxide into oxygen atoms and other chemicals, the researchers said. Some of the oxygen is then transported by winds to the Venusian night side.
“This detection of atomic oxygen on Venus is direct evidence of the action of photochemistry – triggered by solar UV radiation – and the transport of its products by the winds of Venus’ atmosphere,” said Helmut Wiesemeyer, astrophysicist and co-author of the study. Max Planck Institute for Radio Astronomy in Germany.
“On Earth, our life-protecting stratospheric ozone layer represents a well-known example of such photochemistry,” Wiesemeyer added.
On Venus, there is a layer of clouds containing sulfuric acid up to a height of about 40 miles above the planetary surface, with hurricane-force winds blowing in the opposite direction of rotation of the planet. About 75 miles above the surface, strong winds blow in the same direction as the planet’s rotation.
Oxygen was found to be concentrated between these two fierce layers, at an altitude of about 60 miles. The oxygen temperature ranged from about minus 184 degrees Fahrenheit on the day side of the planet to minus 256 degrees Fahrenheit on the night side.
Methods previously used to detect Venusian dayside oxygen were indirect, based on measurements of other molecules in combination with photochemical models.
Venus, with a diameter of about 7,500 miles, is slightly smaller than Earth. In our solar system, Earth resides comfortably in the “habitable zone” around the sun – the distance considered neither too close nor too far from a star to support life, with Venus near the inner limit and Mars close to the external border. edge.
“We are still at the beginning of understanding the evolution of Venus and why it is so different from Earth,” Hübers said.