The United Arab Emirates’ Mars orbiter has captured the best images ever of the Red Planet’s scattered auroras. These images from the Hope spacecraft may help us understand how Mars lost the thicker atmosphere it had billions of years ago.
Auroras occur when high-energy particles slam into a world’s atmosphere, imparting energy to the atoms in the air and making them glow. On Earth, these particles are steered towards the poles by our planet’s magnetic field, but Mars doesn’t have a similar global magnetic field.
However, parts of the Martian crust are still magnetised because the planet once had a magnetic field, and a phenomenon called a discrete aurora can occur over these magnetic zones.
The patchy glow of Mars’s auroras should be visible at night-time, but it has never been seen in visible light. “The aurora are faint, and all of the instruments sensitive to visible light at Mars are designed to take pictures under daylight conditions,” says Justin Deighan at the University of Colorado Boulder, a member of the mission team.
The Hope probe took its pictures in ultraviolet light, at shorter wavelengths than other spacecraft have used to image Mars, which allowed it to capture the auroras in more detail.
Understanding the discrete auroras on Mars could help researchers figure out how it transformed from a possibly habitable world with a thick atmosphere to the dry, nearly airless planet we see today. “The question is, how is energy getting into the system and driving away the upper atmosphere, and aurora gets right to the heart of that,” says Deighan.
Hope captured these images shortly after it entered orbit around Mars in early 2021. Its mission is planned to last two years, so we should be able to examine these auroras in more detail as the mission goes on.
“We are able to capture these kinds of images very regularly, so we expect more frequent images of the aurora whenever they happen, and that will allow us to study more the discrete aurora and why they happen,” says Hessa Al Matroushi, the mission’s science lead.
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