Rocks slowly eroding away make sand all the time on Earth. Violent asteroid impacts, however, could be a significant factor in the formation of fresh sand on Mars.
Recent research reveals that glass spheres formed in the tremendous heat of impacts make up to to 25% of the Martian sand. According to planetary scientist Briony Horgan and colleagues from Purdue University, as wind-blown sand sculpts the Martian surface, this discovery shows how asteroid impacts continue to shape Mars long after the collisions take place. The group will report its findings on August 18 at the Meteoritical Society’s 85th Annual Meeting in Glasgow, Scotland.
Horgan and colleagues identified the minerals in Martian sand by analysing different wavelengths of visible and infrared light reflected from the planet’s surface using data gathered by satellites circling Mars. The scientists discovered glass traces all around the world, but especially at higher latitudes.
Volcanic eruptions, which are known to make glass when magma and water meet, might be one reason for all that glass. The northern plains of Mars, which contain the most glass, are strikingly devoid of volcanoes, the researchers remark. That disqualifies volcanic eruptions as the cause in that area and implies that far more catastrophic occurrences, such as asteroid strikes, may be at play.
According to Steven Goderis, a geochemist from the Vrije Universiteit Brussel in Belgium who was not involved in the study, it is a reasonable explanation. Often Mars is seen as a volcanic planet. But there’s also a very strong impact component, and this is often overlooked.”
The intensity of the collision melts neighbouring rocks and propels them into the sky when an asteroid collides with a stony planet like Mars at a speed of several kilometres per second. That molten shrapnel breaks up into approximately spherical particles the size of sand grains. Impact spherules, which are those glass fragments, eventually shower back upon the globe.
Horgan and her coworkers estimate that during the last 3 billion years, asteroid strikes may have reasonably covered Mars’ surface with a layer of impact spherules that is about half a metre thick. All of that debris contributed to the sand that naturally accumulated on Mars as a result of erosion. According to Horgan, impacts “Impacts helped supply sand to the surface continuously over time,”
In the future, researchers could have the chance to examine Martian impact spherules. Sand and rock samples from Mars are now being stored by NASA’s Perseverance rover in preparation for their eventual return to Earth. Horgan finds that to be thrilling. “The record of all this is in the sand”
image credits: JPL-CALTECH/NASA
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