Mars' auroras happen all over the planet and UAE's Hope orbiter captures new images

When barrages of charged protons and electrons erupted from the sun head our way, Earth’s magnetic field deftly deflects them around the planet. This buffeting generates shimmering, glowing curtains of colour known as the aurora borealis in the northern hemisphere’s polar regions and aurora australis in the south.

That same phenomenon happens on Mars, too. But there it is not just the northern lights and southern lights, but also the equatorial lights, mid-latitude lights, eastern lights, western lights — all around the planet.

The Hope spacecraft, launched by the United Arab Emirates and orbiting the red planet since February, has captured unique images of these dancing atmospheric lights, known as discrete auroras.

An artist’s impression of how Mars’ discrete aurora might be viewed from different views including the surface of Mars when the emissions of light from the fleeting phenomenon extend into the visible spectrum as predicted by theory. Image credit: UAE/Twitter/@HopeMarsMission

Mission officials released the pictures Wednesday.

“It will allow new doors of study to be opened when it comes to the Martian atmosphere,” said Hessa al-Matroushi, the science lead for the first interplanetary mission by the UAE, “and how it interacts with the solar activity.”

The glows on Mars are not just at the top and bottom of the planet, because the magnetic field around the planet has largely died out as molten iron in the interior cooled. But parts of the crust of Mars that hardened several billion years ago when Mars did have a global magnetic field preserve some of that magnetism.

“They’re very patchy and unevenly distributed,” said Justin Deighan, the deputy science lead.

While Earth’s magnetic field is like one large bar magnet, on Mars, “it’s more like you took a bag of magnets and dumped them into the crust of the planet,” said Deighan, a researcher at the University of Colorado’s Laboratory for Atmospheric and Space Physics, which is collaborating with the UAE on the mission. “And they’re all pointed different ways. And they have different strengths.”

The disjointed magnetic fields act as lenses to shepherd solar wind particles to different parts of the Martian atmosphere, but then they hit atoms and molecules in the upper atmosphere, generating the glow of auroras.

Previous Mars orbiters have also observed the auroras, but Hope, with a high-altitude orbit that varies from 12,400 miles to 27,000 miles above the surface, can take in a global view of the night side of Mars.

Taking pictures of auroras was not part of the core science observations planned for the Hope spacecraft, which entered orbit around Mars in February. The mission is trying to study dynamics of the Martian atmosphere near the surface that influence how fast the atmosphere of Mars is leaking into space.

But even before the probe launched, scientists realized that one of the instruments, which makes observations in the far-ultraviolet part of the spectrum to measure levels of oxygen and hydrogen in the upper atmosphere, might be able to pick out the auroras as well.

“Our guess was, we would see something, but we weren’t sure how often it was going to be,” Deighan said. “What’s really fantastic is that we basically saw it right away, and with such clarity. It was unambiguous.”

NASA’s MAVEN spacecraft can also take similar pictures of the Martian auroras when its elliptical orbit takes it farther from the planet, and it can also directly measure and identify the solar particles creating the light show when it is passing close by. But it cannot make both measurements simultaneously.

By coordinating Hope’s aurora photographs with MAVEN’s particle measurements, planetary scientists might be able to put together a more complete understanding of the night lights of Mars.

“Having two spacecraft is really what you want for this,” Deighan said.

Kenneth Chang c.2021 The New York Times Company

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