A new map shows how the solar wind rains everywhere on Mars

In a joint effort between NASA’s MAVEN spacecraft and the United Arab Emirates Mission to Mars (EMM), scientists have observed an unusually chaotic interaction between the solar wind and Mars’ upper atmosphere, resulting in the appearance of unique ultraviolet auroras. This phenomenon represents an unusual occurrence in Martian space weather, and scientists are excited to take advantage of future collaboration between spacecraft to monitor recurring events.

Strange, irregular auroras caused by the solar wind have been observed twice since August 11 and August 30 this year. The aurora borealis have been observed regularly since 2018, but they usually occur in a smooth and even range covering the planet. In contrast, the aurora borealis last month was intermittent, variable, and occurs locally.

It’s a specific type of aurora called a proton aurora, and it occurs on the day side of the planet when hydrogen atoms from the sun, stripped of their electron, explode toward the red planet and penetrate the ‘arc shock’, a magnetic barrier that naturally protects Mars’ atmosphere. Some protons are able to bypass the arc shock by stealing electrons from the crowded region of space around Mars, becoming neutral and breaking up the upper atmosphere. The result is an ultraviolet aurora, which, so far, seemed to always occur as a coherent whole across the face of Mars, but is now seen in distinct patches.

Proton auroras occur on Earth as well, but they cannot be seen with the human eye, and are rare due to Earth’s stronger magnetic field.

The top image shows the formation mechanism of the natural proton auroras that was first discovered in 2018. The bottom image shows the newly discovered formation mechanism of the incomplete proton auroras. Credits: Emirates Mars Exploration Mission / Emirates Space Agency.

It took notes from both Maven and EMM to understand what was going on. EMM’s Mars Ultraviolet Spectrometer (EMUS) instrument is constantly scanning the planet’s upper atmosphere, monitoring for evidence of atmospheric escape into space and changes in composition. Its detector is ideal for capturing ultraviolet light from the proton aurora.

Meanwhile, MAVEN captures in-situ data, “feeling” the solar wind plasma as it passes through the magnetometer and ion analyzers.

When the EMM data were compared with the MAVEN data, it was clear that the incomplete proton auroras were the result of the extremely turbulent plasma environment at the time of the events.

Mike Chavin of the University of Colorado Boulder explained, “EMM observations suggested that the aurora was so widespread and disorganized that the plasma environment around Mars must have been really turbulent, to the point that the solar wind was directly affecting the upper atmosphere wherever we observed auroral emission.” …by combining EMM auroral observations with MAVEN measurements of the auroral plasma environment, we can confirm this hypothesis and determine that what we were seeing was essentially a map of where the solar wind rains on the planet.”

Pictures from August 5 show typical weather conditions (no unusual activity). On August 11 and August 30, the instrument observed intermittent auroras that indicate turbulent interactions with the solar wind.
Credits: EMM / EMUS

Essentially, it was a temporary breakdown of Mars’ natural defenses against solar radiation, when particles were able to take advantage of the chaotic space weather to find a way to reach the planet’s atmosphere.

MAVEN arrived at Mars in 2014 and EMM joined it in 2021. There are more than six probes in Mars orbit, each with different specialties and capabilities. Working together, they can help us understand Mars in a way they can’t do alone, including studying its unique auroras.

Learn more:

Evan Goff,”Mars has aurora borealis too, we can’t see it. ” universe today.

Willow Reed,”MAVEN and EMM are making the first observations of an incomplete proton auroras on Mars.NASA.

Bill Stegerwald/Nancy Jones,”NASA’s MAVEN spacecraft discovers that “stolen” electrons enable unusual auroras on Mars.NASA.