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28 апреля 2018, 15:12

Cracks in Martian Rocks Help Bring Planet’s Watery Past Into Focus


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While well-heeled Earthlings pack for their first trip to Mars, scientists are revealing fresh details about the red planet’s ancient climate.

Early last year, analysts announced the discovery of possible desiccation cracks in Gale Crater, once filled by lakes 3.5 billion years ago.

“We are now confident that these are mud cracks,” lead author Nathaniel Stein, a geologist at the California Institute of Technology in Pasadena, said in a statement.

These decorative structures form when wet, muddy sediment dries up and contracts; naturally occurring mud cracks are the result of residue once saturated with water.

In this case, their position near the center of the basin, rather than at the edge, suggests water levels rose and fell “dramatically” over time, according to The Geological Society of America (GSA).

“The mud cracks show that the lakes in Gale Crater had gone through the same type of cycles that we see on Earth,” Stein explained in a study recently published in the journal Geology .

Tapping into NASA’s Curiosity rover, researchers focused on a coffee table-sized slab of rock called “Old Soaker,” which is covered in polygons just like those seen in Earthly desiccation features.

Curiosity mastcam image of the Squid Cove rock slab taken on Sol 1555 (via The Geological Society of America)

A closer physical and chemical look at the shapes—confined to a single layer of stone, with sediment filling their cracks—proved what scientists have long believed: that the figures are the result of exposure to air (not thermal or hydraulic fracturing).

It’s no secret that the Gale Crater once contained lakes. But when and how liquid water existed on the planet remains a mystery.

NASA made a breakthrough in 2015, providing evidence that water may still exist on the surface of Mars. The longer and harder they looked, though, the less H2O scientists believe there is: Recent findings tip about the same volume as Earth’s Atacama Desert or the Antarctic Dry Valleys.

Analysts were stumped, however, by new climate data released in February that suggests the planet’s atmosphere may not have been warm enough to melt ice into water.

The universe, after all, is a mystery. One that the Curiosity rover is helping to unravel, one crevice at a time.

“The mud cracks are exciting because they add context to our understanding of this ancient lacustrine system,” Stein said. “We are capturing a moment in time. This research is just a chapter in a story that Curiosity has been building since the beginning of its mission.”

Early this year, data from two orbiting spacecraft revealed ice cliffs at least 100 meters (328 feet) thick, which may come in handy as a water source for future human exploration.

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Source: https://www.geek.com/science/cracks-in-martian-rocks-help-bring-planets-watery-past-into-focus-1737583/?source=science