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Curiosity finds an ancient oasis on Mars square

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The above video provides a concise background to what has been learned with the NASA Curiosity Rover, which has been exploring the Gale crater on Mars since 2012. Curiosity, together with other Mars researchers, has proved that the red planet must once have been warmer and wetter, probably with liquid water on the surface. Could life have taken root there? Maybe, and that's part of what scientists have been so fascinated with. This week (October 7, 201

9) scientists from NASA's Jet Propulsion Laboratory in Pasadena, California, announced another new study on marine water published in the journal Nature Geoscience (19459008). A statement about the new work painted a vivid picture of Mars billions of years ago:

Imagine ponds on the floor of Gale Crater, the 150-kilometer-wide ancient basin that Curiosity explores. Creeks could have washed around the walls of the crater and run to its bottom. Watch the story in quick-forward, and you would see these waterways overflow and then dry out, a cycle that is likely to recur over millions of years.

This is the landscape described by scientists of curiosity.

new paper interprets the rocks found by Curiosity – enriched with mineral salts – as evidence of shallow salt ponds that existed on the Martian surface billions of years ago. The rocks prove that these ponds on Mars have undergone episodes of overflow and dehydration. NASA commented:

The deposits serve as a watermark generated by climate variability as the Martian environment passed from a wetter to today's icy desert.

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  This is rock, but it looks like a dry lake bed with many narrow, right-angled cracks.

Enlarge. | Possible mud cracks in the Martian rocks. Earth scientists call this Mars rock plate Old Soaker . It could have formed more than 3 billion years ago from the drying out of a layer of mud. The view extends from left to right over approximately 4 feet (1.2 meters) and combines three images taken with the Mars Hand Lens Imager Camera (MAHLI) on the arm of the NASA Curiosity Mars Rover. Read more about this picture.

William Rapin of Caltech is the main author of the new paper. He said:

We went to Gale Crater for preserving this unique record of a changing Mars. Understanding when and how the climate developed on the planet is another mystery: when and how long was Mars able to support the life of microbes on the surface?

Rapin and his co-authors describe salts found at an altitude of 500 feet (150 meters high) of sedimentary rocks called Sutton Island which Curiosity visited in 2017. The mud cracks at one point are so much like a dry lake that scientists have nicknamed the place . Old Soaker . NASA said:

… the team already knew that there are sometimes drier periods in the region. The salts of Sutton Island suggest, however, that the water also concentrated in brine.

When a lake dries out, stacks of pure salt crystals usually remain. But the salts of Sutton Island are different: on the one hand they are mineral salts, not table salt. They are also mixed with sediments, suggesting that they crystallized in a humid environment – possibly directly beneath evaporating shallow pools filled with salt water.

Given the similarity of Earth and Mars in their early days, Rapin suspected that Sutton Island might have been similar to salt lakes on South America's Altiplano [in west-central South America, the place where the Andes are widest]. Streams and rivers that flow from mountain ranges into this arid plateau lead to closed basins that resemble Mars' old Gale crater. Lakes on the Altiplano are as strongly influenced by the climate as Gale.

Rapin added:

During drier periods, the Altiplano Lakes become flatter and some can dry out completely. The fact that they are free of vegetation makes them look a bit like Mars.

  Complex wheel machine on light brown rock landscape against cloudy sky with translucent sun.

Show as panorama. | This self-portrait of the NASA Mars Rover Curiosity combines 66 images made by Rover's MAHLI imaging system on the 177th Mars Day (or Sol) of Curiosity's Mars work (February 3, 2013).

The curiosity science team now sees a cycle from wet to dry over long periods on Mars. Project scientist Ashwin Vasavada of JPL said:

As we climb Mount Sharp, we see a general trend from a humid to a drier landscape. However, this trend was not necessarily linear. It was more likely to be chaotic, including periods of dryness such as those on Sutton Island, followed by wetter periods …

Read more about this new study on NASA / JPL-Caltech

  Part of a marsh beside a hill where blue water slowly dries and dry land arises.

This animation shows the Sutton Island model of drying lakes on Mars. Sutton Island is a 150-meter section of sedimentary rocks on Mount Sharp, the central mountain in Gale Crater that Curiosity has explored since 2012. The model suggests that electricity from Mount Sharp flows to the ground from Gale Crater. Salty ponds may have been left behind as the area has dried up over time. The mineral salts-enriched rocks found here by Curiosity indicate that the water slowly disappeared and there is a possible persistent cycle of drying and overflowing. Image about ASU Knowledge Enterprise Development / Michael Northrop / NASA.

Conclusion: Scientists working with the Curiosity Rover have found salt-enriched rock at a place called Sutton Island on Mars. The rocks suggest that saltwater ponds existed on Mars billions of years ago.

Source: A high salinity interval in the old Gale crater lake on Mars

  Deborah Byrd

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