Clear as mud: Desiccation cracks help reveal the shape of water on Mars

April 19, 2018, Geological Society of America

Curiosity Mastcam image of the Old Soaker rock slab taken on Sol 1555. The red-toned bed is covered by ridges that are the remnants of sediment that filled cracks that formed in drying lake in Gale Crater some ~3.5 billion years ago. The slab is about 80 cm across. Credit: NASA.
As Curiosity rover marches across Mars, the red planet's watery past comes into clearer focus.

In early 2017 scientists announced the discovery of possible desiccation cracks in Gale Crater, which was filled by lakes 3.5 billion years ago. Now, a new study has confirmed that these features are indeed desiccation cracks, and reveals fresh details about Mars' ancient climate.

"We are now confident that these are mudcracks," explains lead author Nathaniel Stein, a geologist at the California Institute of Technology in Pasadena. Since desiccation mudcracks form only where wet sediment is exposed to air, their position closer to the center of the ancient bed rather than the edge also suggests that lake levels rose and fell dramatically over time.

"The mudcracks show that the lakes in Gale Crater had gone through the same type of cycles that we see on Earth," says Stein. The study was published in Geology online ahead of print on 16 April 2018.

The researchers focused on a coffee table-sized slab of rock nicknamed "Old Soaker." Old Soaker is crisscrossed with polygons identical in appearance to desiccation features on Earth. The team took a close physical and chemical look at those polygons using Curiosity's Mastcam, Mars Hand Lens Imager, ChemCam Laser Induced Breakdown Spectrometer (LIBS), and Alpha-Particle X-Ray Spectrometer (APXS).

Curiosity Mastcam image of the Squid Cove rock slab taken on Sol 1555. The red-toned bed is covered by ridges that are the remnants of sediment that filled cracks that formed in drying lake in Gale Crater some ~3.5 billion years ago. The cracks terminate at the underlying bed, which is coarser and did not fracture. The slab is about 60 cm across. Credit: NASA.

That close look proved that the polygons—confined to a single layer of rock and with sediment filling the cracks between them—formed from exposure to air, rather than other mechanisms such as thermal or hydraulic fracturing. And although scientists have known almost since the moment Curiosity landed in 2012 that Gale Crater once contained lakes, explains Stein, "the mudcracks are exciting because they add context to our understanding of this ancient lacustrine system."

"We are capturing a moment in time," he adds. "This research is just a chapter in a story that Curiosity has been building since the beginning of its mission."

Explore further: Mars rover Curiosity examines possible mud cracks

More information: N. Stein et al. Desiccation cracks provide evidence of lake drying on Mars, Sutton Island member, Murray formation, Gale Crater, Geology (2018). DOI: 10.1130/G40005.1

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4 comments

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Solon
1 / 5 (2) Apr 20, 2018
The same effect can be produced by the use of microwaves, as can many other features on the Martian surface.
jonesdave
2 / 5 (4) Apr 20, 2018
The same effect can be produced by the use of microwaves, as can many other features on the Martian surface.


All jolly interesting, but Mars hasn't been in a gigantic microwave oven any time recently. It's due to water.
Solon
1 / 5 (3) Apr 20, 2018
"but Mars hasn't been in a gigantic microwave oven any time recently."

If you were genuinely interested in science you might take the time to study the processes used industrially for the drying, melting, fracturing etc of various rock types. Microwaves can be produced by processes other than ovens, but you would seem to have no understanding of such science.
Shootist
5 / 5 (1) Apr 20, 2018
The same effect can be produced by the use of microwaves, as can many other features on the Martian surface.


Superman is susceptible to krytonite as well.

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