Scientists detect oxygen in noxious atmosphere of Venus

Oxygen accounts for about 21 percent of Earth's air, with the rest of our atmosphere primarily nitrogen. And most living things - including people, as we well know - need oxygen to survive.

Earth's planetary neighbor Venus offers quite a different story. Its thick and noxious atmosphere is dominated by carbon dioxide - 96.5 percent - with lesser amounts of nitrogen and trace gases. Oxygen is nearly absent. In fact, with Venus getting far less scientific attention than other planets such as Mars, the direct detection of its oxygen has remained difficult.

Using an instrument aboard the SOFIA airborne observatory - a Boeing 747SP aircraft modified to carry an infrared telescope in 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, which consists of a single oxygen atom, differs from molecular oxygen, which consists of two oxygen atoms and is breathable.

The researchers directly detected oxygen for the first time on the side of Venus facing the sun - where it actually is produced in the atmosphere - as well as detecting it on the side facing away from the sun, where it previously was spotted by a ground-based telescope in Hawaii. Venus rotates much more slowly than Earth.

"The Venus atmosphere is very dense. The composition is also very different from Earth," said German Aerospace Center physicist Heinz-Wilhelm Hübers, lead author of the study published in the journal Nature Communications.

The thick atmosphere on the second planet from the sun traps in heat in a runaway greenhouse effect.

"Venus is not hospitable, at least for organisms we know from Earth," Hübers added.

The oxygen is produced on the planet's day side by ultraviolet radiation from the sun that 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 proof for the action of photochemistry - triggered by solar UV radiation - and for the transport of its products by the winds of Venus' atmosphere," said astrophysicist and study co-author Helmut Wiesemeyer of the 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.