In a joint effort by NASA’s MAVEN spacecraft and the Emirates Mars Mission (EMM) of the United Arab Emirates, scientists have observed an unusually chaotic interaction between the solar wind and the upper atmosphere of Mars, creating a unique ultraviolet aurora. This phenomenon represents an unusual occurrence in Martian space weather, and scientists are excited to take advantage of future spacecraft collaboration to monitor repeat events.
A strange, spotty aurora created by the solar wind has been observed twice, on August 11 and 30 this year. Similar auroras have been observed regularly since 2018, but they usually occur in a smooth, even band covering the planet. The aurora borealis last month was spotty, variable and local, in contrast.
This is a specific type of aurora, called a proton aurora, and occurs on the planet’s dayside when the Sun’s hydrogen atoms, stripped of electrons, explode toward the red planet and penetrate the “bow shock,” a magnetic barrier that naturally protects the atmosphere Mars. Some of the protons are able to bypass the direction of impact, stealing electrons back from the busy space around Mars, becoming neutral and breaking through to enter the upper atmosphere. The result is the ultraviolet aurora, which until now always seemed to be a whole on the surface of Mars, but now it was seen in separate areas.
Proton auroras also occur on Earth, but they cannot be seen by the human eye and are rarer due to Earth’s stronger magnetic field.
It took observations from Maven and EMM to figure out what was going on. The EMM’s Ultraviolet Mars Spectrograph (EMUS) continuously scans the planet’s upper atmosphere, watching for evidence of atmospheric escape into space and changes in composition. Its detector is ideally suited to capture the ultraviolet light produced by the proton aurora.
MAVEN, meanwhile, is capturing data in situ by “sensing” the plasma of the solar wind as it passes by using its magnetometer and ion analyzers.
When the EMM data were compared with the MAVEN data, it became clear that the patchy proton glow was the result of a highly disturbed plasma environment at the time of the events.
Mike Chaffin of the University of Colorado Boulder explained that “the EMM observations show that the aurora was so widespread and disorganized that the plasma environment around Mars must have been really disrupted, to the point where the solar wind was directly affecting the upper atmosphere wherever we observed auroral radiation… By combining the EMM aurora observations with MAVEN measurements of the auroral plasma medium, we can confirm this hypothesis and determine that what we saw was essentially a map of where the solar wind was pouring onto the planet.”
It was essentially a temporary breach in Mars’ natural defenses against solar radiation, when particles were able to take advantage of the chaotic space weather to find their way into the planet’s atmosphere.
MAVEN arrived at Mars in 2014 and was joined by EMM in 2021. There are more than half a dozen probes in Martian orbit, each with different specialties and capabilities. Working together, they can help us understand Mars in ways they can’t do on their own, including studying its unique auroras.
Evan Gough, “Mars also has auroras, but we just can’t see them.” The universe today.
Willow Reed, “MAVEN and EMM make first observations of spotted proton glow on Mars.“NASA.
Bill Steigerwald/Nancy Jones, “NASA’s MAVEN spacecraft has discovered that “stolen” electrons can create unusual aurora on Mars.“NASA.