January 18, 2017

Curiosity to investigate strange ‘mud cracks’ on Martian surface

NASA’s Curiosity rover has found evidence of formerly muddy ground on Mars, according to a recent news release from the space agency.

In recent weeks, NASA scientists have been investigating pieces of stone cross-hatched with small ridges, which seems to have formed as cracks in drying mud. The Curiosity team has been particular focused on a triangular slab of rock they dubbed “Old Soaker.”

"Mud cracks are the most likely scenario here," said Nathan Stein, a Curiosity science team member. "Even from a distance, we could see a pattern of four- and five-sided polygons that don't look like fractures we've seen previously with Curiosity.

"It looks like what you'd see beside the road where muddy ground has dried and cracked,” he added.

Could be the First Mud Cracks Found by the Mission

If the team were able to confirm this origin story, it would be the first mud cracks found by this rover mission. Curiosity has discovered proof of ancient lakes in older, lower-lying stone layers as well as in younger mudstone that sits above Old Soaker.

The cracked exterior was established more than 3 billion years ago and was then buried by other layers of sediment, forming into stratified stone. Later, wind erosion stripped the layers above Old Soaker. Material that had stuffed the cracks was more erosion resistant, leaving a pattern of raised ridges.

The team used Curiosity to investigate material that filled in the cracks in Old Soaker, mostly windblown dust or sand. Another kind of cracking with numerous examples discovered by Curiosity occurs after sediments have solidified into stone. Pressure from the buildup of overlying sediments can result in underground cracks in the stone. These fractures usually have been stuffed by minerals carried by groundwater moving through the cracks, often creating veins of calcium sulfate.

Both kinds of crack-filling material were discovered at Old Soaker. This may reveal several generations of breaking: First the mud cracks first, then sediment accumulates in the cracks, then underground fracturing occurs and finally veins develop.

"If these are indeed mud cracks, they fit well with the context of what we're seeing in the section of Mount Sharp Curiosity has been climbing for many months," said Ashwin Vasavada, a Curiosity scientist at NASA. "The ancient lakes varied in depth and extent over time, and sometimes disappeared. We're seeing more evidence of dry intervals between what had been mostly a record of long-lived lakes."


Image credit: NASA JPL