NASA’s Curiosity Mars Rover may have found evidence of an ancient oasis on the Red Planet, within the 150-km wide Gale crater. The discovery, published in the Nature Geoscience journal, throws up questions about whether Mars could have sustained microbial life in the past, say the scientists who made the discovery.
In a recent statement on its website, NASA said that 3.5 billion years ago, the Gale Crater could have had ponds at the base, and streams running down along its walls. Over successive millennia, these water bodies went through several cycles of drying and overflowing, as the Crater filled up with soil brought in by water and wind. This theory is strengthened by the discovery of rocks enriched with mineral salts at a 150-metre tall section of sedimentary rock at a location called ‘Sutton Island’. NASA’s scientists say the rocks are evidence of “shallow briny ponds that went through episodes of overflow and drying” at different points in Martian history.
Significantly, the mineral composition of the Sutton Island rocks suggests that they were crystallised just below ponds filled with brine (saline) water, which could have resembled saline water bodies on Earth.
“We went to Gale Crater because it preserves this unique record of a changing Mars,” lead author William Rapin of Caltech was quoted as saying in NASA’s statement. “Understanding when and how the planet’s climate started evolving is a piece of another puzzle: When and how long was Mars capable of supporting microbial life at the surface?”
NASA also released an image of a rock slab called “Old Soaker”, clicked by the Mars Hand Lens Imager (MAHLI) camera on the Curiosity rover in December 2016. A three-foot area of Old Soaker, which is located within the Gale Crater, is seen in the composite photograph. The photo shows a distinct set of cracks that may have formed when a mud layer dried over 3 billion years ago. The Sutton Island discovery appears to confirm what scientists suspected after analysing the image of Old Soaker about drier periods succeeding wetter phases in the Gale Crater.
Further clues as to Mars’ changing climate are awaited as Curiosity climbs Mount Sharp, a slope in the Gale Crater. The rover is headed towards a sulphate-bearing unit on the Mountain that may have formed in a drier climate than existed lower down the Crater. In 2015, the Curiosity Rover had confirmed that ancient lakes existed on Mars after analysing the lower end of the Gale Crater. The same year, NASA also found evidence that suggests liquid water is flowing intermittently on the surface of the Red Planet even today.
A few days ago, NASA chief scientist Jim Green told a newspaper that humans may be close to finding life on Mars, but added that the world may not be ready for a discovery of that magnitude. NASA and the European Space Agency will launch two Mars-bound rovers in 2020, and the NASA probe, Mars2020, aims to bring back soil samples from the Red Planet for the first time.
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