Study: Ancient Mars May Have Had Wet, Dry Periods
2023-08-21
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1Researchers say they have found evidence that ancient Mars experienced both wet and dry climate cycles.
2The new evidence is based on data collected by an exploring vehicle on Mars, called Curiosity.
3The explorer, or rover, is operated by the American space agency NASA.
4Scientists say the finding suggests Mars may have once held the right conditions to support life.
5They describe their findings in a study appearing this month in the publication Nature.
6Today, Mars is a dusty, cold desert.
7But past research has shown the planet was once home to a large system of rivers and lakes.
8Many studies have suggested the presence of water billions of years ago may have created conditions to support life.
9But there has been no clear evidence Mars also experienced dry periods.
10The Curiosity rover has been exploring Mars' huge Gale crater since 2012.
11The area is believed to have contained a lake at one time and has a large mountain of sediment nearly six kilometers high.
12The researchers said that while climbing the side of the sediment mountain in 2021, Curiosity found salt remains that formed a hexagonal shape in soil that dated back nearly four billion years.
13The rover's instruments identified the shape as cracks in dried mud.
14"When a lake dries up the mud cracks, and when it fills back up, the cracks heal," said William Rapin.
15He is a researcher at France's National Centre for Scientific Research (CNRS) and the lead writer of the study.
16Rapin said when this process is repeated, the cracks position themselves in hexagons, or six-sided shapes.
17This hexagonal evidence suggests there were long dry periods in the Gale Crater area.
18NASA said the evidence that rivers and lakes on ancient Mars began to dry up at times provides evidence that climate cycles repeatedly happened.
19Rapin said the finding is "the first tangible proof" that Mars had a wet-dry climate."
20The researchers say having both wet and dry seasons, as we have on Earth, could have provided the right conditions for life to form on Mars.
21Curiosity and another rover operating on Mars, Perseverance, have already identified evidence of organic compounds that could suggest the presence of past life forms.
22But Rapin noted these building blocks need the right mix of conditions in order to support life.
23"In a world that's too dry, these molecules never have the (chance) to form - nor do they in a world that's too wet," he said.
24Ashwin Vasavada is a project scientist at NASA's Jet Propulsion Laboratory in California.
25He said in a statement, "Over 11 years, we've found ample evidence that ancient Mars could have supported microbial life.
26Now, the mission has found evidence of conditions that may have promoted the origin of life, too."
27Such evidence would never have been found on Earth, Rapin said.
28This is because tectonic plates on our planet repeatedly recycle the surface, burying evidence from before the time life formed.
29Rapin noted this means that studying Mars - which does not have tectonic plates - could help scientists solve the mystery of how life began on Earth.
30"It's pretty lucky of us to have a planet like Mars nearby that still holds a memory of the natural processes which may have led to life," he said.
31I'm Bryan Lynn.
1Researchers say they have found evidence that ancient Mars experienced both wet and dry climate cycles. 2The new evidence is based on data collected by an exploring vehicle on Mars, called Curiosity. The explorer, or rover, is operated by the American space agency NASA. 3Scientists say the finding suggests Mars may have once held the right conditions to support life. They describe their findings in a study appearing this month in the publication Nature. 4Today, Mars is a dusty, cold desert. But past research has shown the planet was once home to a large system of rivers and lakes. Many studies have suggested the presence of water billions of years ago may have created conditions to support life. But there has been no clear evidence Mars also experienced dry periods. 5The Curiosity rover has been exploring Mars' huge Gale crater since 2012. The area is believed to have contained a lake at one time and has a large mountain of sediment nearly six kilometers high. 6The researchers said that while climbing the side of the sediment mountain in 2021, Curiosity found salt remains that formed a hexagonal shape in soil that dated back nearly four billion years. The rover's instruments identified the shape as cracks in dried mud. 7"When a lake dries up the mud cracks, and when it fills back up, the cracks heal," said William Rapin. He is a researcher at France's National Centre for Scientific Research (CNRS) and the lead writer of the study. 8Rapin said when this process is repeated, the cracks position themselves in hexagons, or six-sided shapes. This hexagonal evidence suggests there were long dry periods in the Gale Crater area. NASA said the evidence that rivers and lakes on ancient Mars began to dry up at times provides evidence that climate cycles repeatedly happened. 9Rapin said the finding is "the first tangible proof" that Mars had a wet-dry climate." The researchers say having both wet and dry seasons, as we have on Earth, could have provided the right conditions for life to form on Mars. 10Curiosity and another rover operating on Mars, Perseverance, have already identified evidence of organic compounds that could suggest the presence of past life forms. 11But Rapin noted these building blocks need the right mix of conditions in order to support life. "In a world that's too dry, these molecules never have the (chance) to form - nor do they in a world that's too wet," he said. 12Ashwin Vasavada is a project scientist at NASA's Jet Propulsion Laboratory in California. He said in a statement, "Over 11 years, we've found ample evidence that ancient Mars could have supported microbial life. Now, the mission has found evidence of conditions that may have promoted the origin of life, too." 13Such evidence would never have been found on Earth, Rapin said. This is because tectonic plates on our planet repeatedly recycle the surface, burying evidence from before the time life formed. 14Rapin noted this means that studying Mars - which does not have tectonic plates - could help scientists solve the mystery of how life began on Earth. "It's pretty lucky of us to have a planet like Mars nearby that still holds a memory of the natural processes which may have led to life," he said. 15I'm Bryan Lynn. 16Bryan Lynn wrote this story for VOA Learning English, based on reports from NASA, Agence France-Presse, the French National Centre for Scientific Research and Nature. 17______________________________________________ 18Words in This Story 19crater - n. a big hole left in the ground or an object by a force of impact 20sediment - n. materials that collect at the bottom of a liquid 21crack - n. a line on the surface of something that is damaged 22mud -n. soft, wet soil or clay 23tangible - adj. something that is real and can be seen, touched or measured 24organic - adj. chemicals known to contain carbon 25ample - adj. enough, or more than enough 26origin - v. where something begins or comes from 27_________________________________________________ 28What do you think of this story? We want to hear from you. We have a new comment system. Here is how it works: 29Each time you return to comment on the Learning English site, you can use your account and see your comments and replies to them. Our comment policy is here.