Scientists using NASA’s Mars-orbiting MAVEN spacecraft discovered a mysterious cloud of dust hundreds of miles above the planet’s surface — and no explanation for how it got there.
The Mars Atmosphere and Volatile Evolution spacecraft was on the hunt for remnants of a comet that blitzed Mars in October when it detected the high-altitude dust, scientists said at the Lunar and Planetary Science Conference in Houston on Wednesday.
“We saw something that we were not expecting,” said MAVEN scientist Laila Andersson, with the University of Colorado in Boulder.
The dust cloud surrounds Mars and reaches altitudes more than 1,000 kilometers (621 miles) from the planet’s surface, said MAVEN lead scientist Bruce Jakosky, also with University of Colorado.
“This is the first discovery of a layer or dust or debris at orbital altitudes around Mars,” he added.
Scientists don’t know if the cloud is a temporary or long-lasting phenomenon, nor where it came from.
MAVEN found that the levels of dust varied from orbit to another. Overall, the cloud is denser at lower altitudes, suggesting that the dust rises from the planet’s surface, by some unknown mechanism.
“We think the source is the (Martian) atmosphere, however we have no process to take dust from low altitude to bring it up to 200 kilometers (124 miles). So if the source is the atmosphere, we don’t understand which process is moving them up,” Andersson said.
The dust also could have come from Mars’ moons, Phobos and Deimos, from dust in the solar wind or from comet dust that fills interplanetary space.
“Either way, I think it’s hard to understand how this stuff got here,” Jakosky said.
The dust poses no threat to Mars orbiters, including MAVEN, he added.
MAVEN also spotted aurora glowing in ultraviolet light in Mars’ northern hemisphere. The aurora, similar to Earth’s Northern and Southern Lights, are triggered by charged particles slamming into the atmosphere, which causes gas to glow.
The Martian auroras detected by MAVEN over five days in late December extend far deeper into the planet’s atmosphere than previously observed aurora.
Since Mars doesn’t have a global magnetic field like Earth, charged particles, most likely from the sun, can directly hit the Martian atmosphere.
“This diffuse aurora has never before been seen on Mars,” Jakosky said.