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Cosmic dust may create Mars’ wispy clouds

Magnesium from passing comets could be a key part of the Red Planet’s cloud-starter kit

By
5:08pm, March 13, 2018

HEAD IN THE CLOUDS  The rover Opportunity snapped this picture of wispy clouds drifting through the Martian sky in 2006. New findings suggest the clouds might have condensed around particles of dust from comets.

The seeds for Martian clouds may come from the dusty tails of comets.

Charged particles, or ions, of magnesium from the cosmic dust can trigger the formation of tiny ice crystals that help form clouds, a new analysis of Mars’ atmosphere suggests.

For more than a decade, rovers and orbiters have captured images of Martian skies with wispy clouds made of carbon dioxide ice. But “it hasn’t been easy to explain where they come from,” says chemist John Plane of the University of Leeds in England. The cloud-bearing layer of the atmosphere is between –120° and –140° Celsius — too warm for carbon dioxide clouds to form on their own, which can happen at about –220° C.

Then in 2017, NASA’s MAVEN orbiter detected a layer of magnesium ions hovering about 90

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