Since 2013, NASA’s Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft has been digging into the secrets of the red planet’s atmosphere—and once again, that stellar snooping has paid off. As David Grossman reports for Popular Mechanics, scientists have confirmed that Mars has metal in its atmosphere, a discovery that shows it’s both similar to—and quite different from—Earth.
Scientists describe the find in a paper published in the journal Geophysical Research Letters. Over the last two years, they used MAVEN to detect magnesium, iron, and sodium ions in the aptly named ionosphere—part of Mars’ upper atmosphere. The ions they discovered weren’t just a passing fad, either: They appear to be a permanent feature, just like Earth’s.
Tiny meteoroids are likely to blame for these Martian metals. The meteoroids slam into the atmosphere at high speeds and vaporize. Charged atoms and molecules in the ionosphere suck away some of the metal's electrons, leaving the electrically charged ions behind. That’s what happens on Earth, too.
But those similarities don’t mean that Mars’ and Earth’s atmospheres act exactly the same. Because of Earth’s magnetic field and winds in the ionosphere, metal ions that enter the planet’s atmosphere sort out into neat bands. Metal ions on the red planet, on the other hand, have a more chaotic fate.
Because Mars has no global magnetic field, the organized layers of magnetic ions only form near the localized fields. Scientists think that Mars once was surrounded by a magnetic field like Earth’s, but at some point the field—and Mars’ atmosphere—slipped away. Today, Mars’ spotty magnetic field means that passing comets, and even the Sun, can drag charged particles out of the atmosphere, keeping it thin and impossible for eventual human explorers to breathe.
It all goes to show that Mars and Earth may not have always been that different, writes Grossman. However, the fates of their atmospheres—and the metallic ions inside—were different indeed.
The detection of a permanent metal ion presence in Mars’ atmosphere will be helpful for scientists. "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, similar to the way we use a lofted leaf to reveal which way the wind is blowing," says Joseph Grebowsky of NASA’s Goddard Space Flight Center, who co-wrote the paper, in a press release.
A better understanding of how those ions work—and why they exist—could help scientists start to understand how high-altitude clouds form on Mars, and how the dust of shattered meteoroids affects Mars, Earth and other planets. They may be tiny, but those metal ions seem poised to give big clues to how Mars’ atmosphere evolved and acts today.