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New Clues of Ancient Water on Mars
13 February 2023
EIRNS—Last fall, the Curiosity rover made its way along an area on Mount Sharp, called the “sulfate-bearing unit,” an area enriched with salty minerals. Scientists hypothesized that billions of years ago, streams, and ponds left behind the minerals as the water dried up.
If this hypothesis is correct, then such minerals could offer tantalizing clues as to how and why the Red Planet’s climate changed from being more Earth-like to the frozen desert it is today. The minerals were identified as early as 2012 by the Mars Reconnaissance Orbiter, so scientists and researchers had to wait a long time to pick up more evidence which could be examined “close up” by the rover’s cameras and geological instruments. The NASA website explained, “Soon after arriving, the rover discovered a diverse array of rock types and signs of past water, among them popcorn-textured nodules and salty minerals such as magnesium sulfate (Epsom salt is one kind), calcium sulfate (including gypsum), and sodium chloride (ordinary table salt).” But, the journey to the “sulfate-bearing unit” was a long trek across dangerous terrain alongside Mount Sharp—the rover took over a month just to negotiate through a rocky and sandy pass (called Paraitepuy Pass), an area about 30 meters (98+ feet) long. This “sulfate-bearing unit” was formed earlier in Mars’s history, and formed salty minerals when water flow had slowed to a mere trickle. So, scientists were excited and surprised to discover in recent weeks after careful analysis of the images transmitted back to Earth, that “the mission’s clearest evidence yet of ancient water ripples that formed within lakes. Billions of years ago, waves on the surface of a shallow lake stirred up sediment at the lake bottom, over time creating rippled textures left in rock.” The rover has been making its way up Mount Sharp since 2014; the mountain is about 3 miles tall, and “is made up of layers, with the oldest at the bottom of the mountain and the youngest at the top. As the rover ascends, it progresses along a Martian timeline … [and] having climbed nearly a half-mile above the mountain’s base, Curiosity has found these rippled rock textures preserved in what’s nicknamed the ‘Marker Band’—a thin layer of dark rock that stands out from the rest of Mount Sharp.” Although this particular rock outcropping proved to be too hard for Curiosity to safely drill into it for samples, there are other regions that are selected for exploration. “Far ahead of the Marker Band, scientists can see another clue to the history of Mars’ ancient water in a valley named Gediz Vallis. Wind carved the valley, but a channel running through it that starts higher up on Mount Sharp is thought to have been eroded by a small river. Scientists suspect wet landslides also occurred here, sending car-size boulders and debris to the bottom of the valley. “Because the resulting debris pile sits on top of all the other layers in the valley, it’s clearly one of the youngest features on Mount Sharp. Curiosity got a glimpse of this debris at Gediz Vallis Ridge twice last year but could only survey it from a distance. The rover team hopes to have another chance to view it later this year.” Ashwin Vasavada, Curiosity’s project scientist at NASA’s Jet Propulsion Laboratory in Southern California commented, “This is the best evidence of water and waves that we’ve seen in the entire mission…. We climbed through thousands of feet of lake deposits and never saw evidence like this—and now we found it in a place we expected to be dry.” (https://www.nasa.gov/feature/jpl/nasa-s-curiosity-finds-surprise-clues-to-mars-watery-past ; https://mars.nasa.gov/msl/mission-updates/9237/sols-3551-3552-through-the-pass-we-go/ ) [jgw] For more information as to how Curiosity communicates with Earth, please see https://mars.nasa.gov/msl/mission/communications/ |
