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Scientists make first direct detection of atmospheric sputtering on Mars

A small team of planetary scientists, astrophysicists and space flight researchers affiliated with several institutions in the U.S. and one in France has made the first direct detection of atmospheric sputtering on Mars.

In their paper in the journal Science Advances, the group describes how they used data from NASA's MAVEN probe to determine that argon densities in a part of the Martian atmosphere vary depending on the behavior of incoming solar wind and its electric field, compared to argon densities at different altitudes that remain consistent and explain why it offers evidence of atmospheric sputtering on Mars.

Atmospheric sputtering is a process whereby ions in the solar wind knock planetary atmospheric particles into space. Scientists studying Mars have long suspected that atmospheric sputtering played a major role in making the planet both cold and dry. Atmospheric sputtering on Mars, they note, would be possible because of its lack of a planet-wide magnetic field.

The work by the team involved poring over nine years' worth of satellite data along with data from NASA's MAVEN probe, which has been circling Mars for about 11 years. In so doing, they found evidence of argon densities at 350 kilometers above the surface varying depending on where the sun sat relative to a given part of the planet, compared to argon densities closer to the ground, where such densities were found to remain nearly constant.

This finding, the team explains, showed lighter isotopes varied in number at higher altitudes, at times leaving behind heavier isotopes. Ongoing atmospheric sputtering is the likely reason for the difference, the team notes. Adding to the evidence was the observation of the impact of a solar storm on the Martian atmosphere—it made the differences in argon densities more pronounced.

The researchers suggest their findings not only show that there is ongoing atmospheric sputtering on Mars, but that it has very likely been going on for a very long time, backing up theories suggesting it has been mainly responsible for the loss of water on Mars' surface and its atmosphere—they note that earlier in Mars' history, ultraviolet light from the sun shone much more intensely, which likely meant higher levels of atmospheric sputtering.