The mystery of ancient water Mars is deepening. It turned out that the early atmosphere of the Red Planet, possessed a hundred times less carbon dioxide than is necessary to maintain the temperature required for liquid water.
Although now Mars is a cold and dry desert, but ten-year evidence shows that its surface was once covered by rivers, lakes, and possibly seas with oceans. Dark narrow lines appear on Mars, as if hinting that water has flowed down the slopes every spring. And where water is known, there is life. So Mars could shelter life, and some of its forms may still be present on the planet.
“The watery environment that once had been the bottom of Gale's crater looks like he was predisposed to life: not hot and not cold, no excessive acidity or alkalinity, and the water is not too salty,” said study author Thomas Bristow, a planetary scientist at NASA's California research center. Ancient Mars should be much warmer than today's planet. Therefore, at the beginning of the work, scientists tried to find signs that it once had enough greenhouse gases, such as carbon dioxide in the atmosphere, which traps solar heat. However, data analysis took the path of carbonate minerals on the surface of Mars, which could be detected only if the atmosphere was once rich in carbon dioxide. To solve the mystery, the researchers studied the information collected by the Curiosity rover, which crossed the lower slopes of the Eolida Mountains, which is 3.4 miles (5.5 km) from the center of Gale Crater.
Scientists analyzed Martian mudstones, siltstone, sandstones and other sedimentary rocks left in the rivers and lakes of the Gale crater 3.5 billion years ago. They did not find carbonates, suggesting that at that time the level of carbon dioxide was tens and hundreds of times lower than that required in climate models for heating early Mars.
But this does not indicate that the planet was not wet. “Sedimentary crater rocks prove the continued presence of liquid water on the surface,” said Bristow.
One explanation is: Mars was once carbonate, but they were destroyed. “However, the nature of the minerals does not confirm this,” says Bristow. “We found no signs of acid exposure.” Another option is that ancient Mars was heated by other greenhouse gases, such as sulfur dioxide, methane or nitrous oxide.
“But the lack of these gases is that they can be quite reactive. Therefore, if you put them in the atmosphere, they won't stay there for a long time, ”said Bristow. “Therefore, warming periods would be short-term, which is inconsistent with the presence of rivers and lakes on the crater, which have been preserved for millions of years.”
Other scenarios include ice caps in which water could be stored, or a change in Martian orbit that made Mars warmer. “Scientists will have to dig even deeper into the topic of mechanisms for stabilizing surface water,” says Bristow.
Now all hopes are pinned on the Curiosity rover, which should take samples of rocks during the climate transition.