MAVEN is finding out how Mars lost its atmosphere

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Apr 13, 2017

Mars has a vanishing atmosphere, and metal ions floating around up there could give us more specifics on the suspects. NASA’s MAVEN (Mars Atmosphere and Volatile Evolution Mission) spacecraft has just directly detected the presence of metal ions in the upper atmosphere of the Red Planet—and their behavior may silently tell us why most of the Martian atmosphere is ending up lost in space.

MAVEN’s mission is to investigate the disappearing atmosphere and determine how Mars lost so much of it, becoming a cold and barren desert planet that (at least based on what we know) is forbidding to most life-forms as we imagine them, when it was possibly a planet that could have supported life billions of years ago. MAVEN has been exploring what is left of the atmosphere, mapping atmospheric particles that escape as the result of solar wind and other phenomena. Scientists use these findings to study ionospheric activity that is evidence of the atmospheric breakdown and figure out about how long it will take to disappear into the darkness.

"MAVEN has made the first direct detection of the permanent presence of metal ions in the ionosphere of a planet other than Earth," said Joseph Grebowsky of NASA's Goddard Space Flight Center, lead author of a recent study published in Geophysical Research Letters. "Because metallic ions have long lifetimes and are transported far from their region of origin by neutral winds and electric fields, they can be used to infer motion in the ionosphere."

What MAVEN is thought to look like as it orbits Mars.

Where the ions are going and why they have been getting away is what Grebowsky and his colleagues were intent on demystifying. Sometimes metal ions are scattered in a planet’s atmosphere by interfering objects such as comets or meteorites, which is something they needed to rule out. The passage of a comet left a trail of them several years ago, but it wasn’t enough to convince his team that these ions were a mainstay in the Martian atmosphere. MAVEN has detected electrically charged iron, magnesium and sodium ions with its Neutral Gas and Ion Mass Spectrometer over the past two years, and the continued detection of these ions despite the absence of interfering objects has finally made scientists confident enough to confirm that metal ions are a permanent feature on another planet.

"MAVEN is observing a polar plume of escaping atmospheric particles," said MAVEN Principal Invesetigator Bruce Jakosky. "The amount of material escaping by this route could make it a major player in the loss of gas to space."

Mars has apparently been losing these ions—and its atmosphere—due to solar phenomena that keep obliterating them. They become electrically charged when exposed to radiation from the sun and outer space, but being charged also means that the sun’s menacing magnetic and electric forces will affect them severely. Intense solar wind whips them toward the poles, while solar flares and even more violent solar storms that result from coronal mass ejections spewing solar stuff into space at millions of miles an hour. Solar assault also explains why Mars is constantly glowing with faint aurorae.

Even though the metal ions in Earth’s atmosphere behave differently, learning about another planet’s atmospheric activity can help us understand our own.

"Elsewhere, the metal ion distributions are totally unlike those observed at Earth," Grebowsky noted. "Observing metal ions on another planet gives us something to compare and contrast with Earth to understand the ionosphere and atmospheric chemistry better."