Mars is often referred to as the Red Planet, but its atmosphere actually has a blue hue. Using the ExoMars Trace Gas Orbiter (TGO) – a spacecraft studying Mars from the European Space Agency (ESA), scientists have for the first time observed the Martian sky emitting a green light.
This effect is known as airglow (or nightglow or dayglow, which refers to the faint emission of light by a planet’s atmosphere – Ed.) and it also occurs on Earth. While there are some similarities to the auroras on our planet, the phenomenon is caused by different mechanisms. Specifically, nightglow “occurs when two oxygen atoms combine to form a molecule of oxygen”, according to ESA. On Mars, this happens at an altitude of about 50 km. In contrast, auroras on Earth occur when charged particles from the Sun collide with the Earth’s magnetic field.
This effect on Mars is called airglow. (Image credit: NASA).
Scientists have been predicting the presence of airglow on Mars for the past 40 years, but it was only first observed a decade ago by ESA’s Mars Express orbiter. In 2020, scientists observed this phenomenon in visible light using TGO, but during the daytime on Mars, not at night. Now, we have observed this phenomenon at night thanks to TGO.
“These new observations are surprising and exciting for future journeys to Mars,” said planetary scientist Jean-Claude Gérard.
Studying nightglow on Mars, which will continue as part of the TGO mission, provides scientists with deeper insights into the processes occurring in the Martian atmosphere.
Researching Mars’ atmosphere could aid in designing future spacecraft for trips to the Red Planet. Understanding this planet better will help scientists create satellites capable of withstanding the drag caused by the Martian atmosphere or designing parachutes that can reduce landing weight onto the planet’s surface.
