The glowing veils of the aurora appear regularly in the sky above Earth and make for great images, but capturing this phenomenon on other planets has always been more of a challenge. Recent observations of Mars and Jupiter have now given scientists unprecedented views of these extraterrestrial aurorae that will help improve our understanding of other planets’ magnetic fields and the space weather weather they experience throughout our solar system.
Behind the glow
Aurorae occur when high-energy particles from space — primarily from the Sun — are funneled toward a planet’s poles by its magnetic field and collide with atmospheric gases. On Earth, this produces the familiar Northern and Southern Lights, with their characteristic green, red, and purple hues.
Jupiter’s aurorae operate on a vastly larger scale. Not only are they physically enormous compared to Earth’s, they’re also hundreds of times more energetic. While Earth’s aurorae primarily result from solar storms, Jupiter has an additional energy source: its immense magnetic field also captures charged particles from its volcanic moon Io. These particles are accelerated to tremendous speeds before slamming into Jupiter’s atmosphere, adding to the solar wind and creating the intense glow.
Mars presents a completely different scenario. Unlike Earth and Jupiter, Mars lacks a global magnetic field, instead possessing what scientists call a hybrid magnetosphere, with localized regions of its crust maintaining small pockets of a magnetic field, primarily in its southern highlands. This unique magnetic environment creates several distinct types of martian aurorae, including both localized and global aurorae, and even auroral glows on the planet’s dayside. The different types of emission result from both the varying energy levels of incoming particles and their interactions with Mars’ unique and complex magnetic environment.
Jupiter’s light show
The JWST image of Jupiter’s aurora shown here was captured by the telescope’s Near-Infrared Camera (NIRCam) on Dec. 25, 2023, showing aurorae that appear to swirl above the planet’s cloud tops.
“We wanted to see how quickly the auroras change, expecting them to fade in and out ponderously, perhaps over a quarter of an hour or so. Instead, we observed the whole auroral region fizzing and popping with light, sometimes varying by the second.” said Jonathan Nichols, team lead from the University of Leicester in the United Kingdom, in a news release.
The unexpectedly variable nature of Jupiter’s aurorae could lead to better understanding the planet’s upper and lower atmosphere. Additionally, Nichols said his team simultaneously studied the planet in ultraviolet light using the Hubble Space Telescope and saw a huge difference. The brightest light in the JWST images did not appear in Hubble’s view, meaning vast quantities of low-energy particles were hitting the planet and causing the infrared glow — and the researchers aren’t yet sure how that sort of situation arises.
To further understand this discrepancy between the telescopes, the team plans to follow up with data from NASA’s Juno spacecraft, which has been studying Jupiter’s magnetosphere from orbit since 2016. The craft contains tools for studying both infrared and ultraviolet light, so it may be able to provide more insight into the cause behind the strange behavior JWST and Hubble observed.
A historic first
While Jupiter’s aurorae have been studied for decades, scientists have also just made a groundbreaking discovery on Mars: the first-ever detection of visible-wavelength aurora from a planetary surface other than Earth. In March 2024, the Perseverance rover’s SuperCam and Mastcam-Z instruments captured a green glow at 557.7 nanometers originating from atomic oxygen in the martian atmosphere.
What makes this discovery particularly significant is how it happened. Researchers used near-real-time simulations to predict when a coronal mass ejection (CME) from the Sun that was directed toward Mars would arrive and cause the aurora. The emission was observed three days after the CME, “suggesting that the aurora was induced by particles accelerated by the moving shock front” of the solar outburst, the team writes in a paper published May 14 in Science Advances. This marks the first time auroral forecasting has successfully predicted such an event on another planet.
The work could open up new avenues for auroral forecasting and space weather prediction at Mars, potentially critical capabilities for ensuring the safety of human missions.
