Emirates Mars mission discovers new type of aurora on Red Planet

A new, worm-like form of aurora seen reaching halfway around Mars has scientists puzzled

A United Arab Emirates space probe has discovered a new, intense form of aurora on Mars, challenging scientists’ understanding of a Red Planet, which, lacking a magnetic field, might not be expected to possess auroras at all.

The UAE’s Hope spacecraft reached Mars in February of 2021 on a mission to study the Martian atmosphere, an arrival that happened to correspond with a solar storm that scientists believe generated the observed aurora. Called a “sinuous discrete aurora,” it consisted of worm-like tendrils of ultraviolet light in the upper atmosphere and snaking halfway around Mars.

“The sinuous discrete aurora was a shocking discovery that in many ways has us scratching our heads and going back to the drawing board,” University of California, Berkeley planetary scientist Rob Lillis said in a statement. “We have ideas, but no solid explanation for why we are observing intense aurora of this shape and at planetary scales.”

At first glance, Mars shouldn’t have any auroras.

On Earth, auroras result when charged particles from the Sun interact with our planet’s global magnetic field and are channeled to one of the two poles, resulting in the Northern and Southern Lights.

But Earth’s magnetic field is generated by our planet’s central dynamo, a solid metallic core spinning inside a liquid metallic outer core.

In 2021, Nasa’s Insight Mission showed that Mars lacks a solid central core, and its large, liquid core is largely made of lighter, non-metallic elements such as oxygen or hydrogen.

No central dynamo means no global magnetic field on Mars, and planetary scientists think the lack of such a field is why Mars has such a thin atmosphere — it was slowly stripped away by the charged particles flowing out from the Sun, the solar wind, over millions of years.

The European Mars Express mission nevertheless observed auroras on Mars for the first time in 2004.

It turned out that sections of the Martian crust still act as powerful magnets even after the planet’s global magnetic field shut off ages ago, generating local magnetic force fields that catch charged particles and generate an aurora glow. The dispersed, discrete nature of these fields is why they appear at various locations over Mars rather than at the poles and on Earth, and why the glowing phenomena are called “discrete” auroras.

That such discrete auroras could stretch as far as they did in the Hope observations, however, suggests something more is going on, according to Lillis. Figuring it out may require data from Hope and other missions, such as Nasa’s Mars atmosphere and volatile evolution, or Maven, orbiter.

“We now have the opportunity to re-examine prior observations of Mars by missions such as MAVEN and Mars Express to search for signatures that could flesh out Hope’s new observations and perhaps help us try and unpick quite what is happening here,” Mr Lillis said in a statement.