Scientists have detected atomic oxygen in the Martian atmosphere for the first time since the last observation 40 years ago.
Atomic oxygen - an elemental form of oxygen that does not exist in Earth's atmosphere - affects how other gases escape Mars and therefore has a significant impact on the planet's atmosphere.
An instrument onboard the Stratospheric Observatory for Infrared Astronomy (SOFIA) - a joint project of Nasa and the German Aerospace Center - helped detect these atoms in the upper layers of the Martian atmosphere known as the mesosphere, Nasa said in a statement.
"Atomic oxygen in the Martian atmosphere is notoriously difficult to measure," said SOFIA project scientist Pamela Marcum.
"To observe the far-infrared wavelengths needed to detect atomic oxygen, researchers must be above the majority of Earth's atmosphere and use highly sensitive instruments, in this case a spectrometer. SOFIA provides both capabilities," Marcum noted.
The scientists could detect only about half the amount of oxygen expected, which may be due to variations in the Martian atmosphere.
The Viking and Mariner missions of the 1970s made the last measurements of atomic oxygen in the Martian atmosphere.
These more recent observations were possible thanks to SOFIA's airborne location, flying between 37,000-45,000 feet, above most of the infrared-blocking moisture in Earth's atmosphere, Nasa said.
The advanced detectors on one of the observatory's instruments, the German Receiver for Astronomy at Terahertz Frequencies (GREAT), enabled astronomers to distinguish the oxygen in the Martian atmosphere from oxygen in Earth's atmosphere.
The findings were presented in a paper published in the journal Astronomy and Astrophysics. SOFIA is a Boeing 747SP jetliner modified to carry a 100-inch diametre telescope.