Billions of years ago, Mars was a very different world from the freezing desert it is today. There was water on its surface. The moment that disappeared into the air or underground has not been well established, and recent research suggests that it may have been wet longer than previously thought. Now China’s Zhurong Mars rover has found more evidence to support this scenario.
The six-wheeled robot explores Utopia Planitia, the largest impact basin on Mars (also the largest in the solar system) at 3,300 kilometers in diameter. It was last visited in the 1970s by NASA’s Viking 2 before Zhurong arrived. The new robotic explorer has found rocks that appear to have formed in the presence of water, scientists report in Science Advances. It’s not something unheard of on Mars, but the timing of their formation is certainly exciting.
The region belongs to the Amazon period, the extended and more modern period of the geological history of Mars. Based on statistical surface impact counts, the area could have been redone 700 million years ago. Without direct analysis, it’s hard to estimate the true age of the rocks, so they could be considerably older than that, but the results still suggest that Mars had liquid water and ice on its surface for a long time. .
The team also discovered that the area explored by Zhurong is made up of a hard layer of soil or hard crust that has different characteristics than what has been seen in other places – such as the one that caused the “death” of the Mole experiment, part of NASA’s InSight mission. The team believe that the particular hard crust – a hard layer on or near the surface of the ground – could have formed by the presence of brackish, slowly evaporating groundwater, cementing the hard crust together.
The presence of liquid water underground in the recent geological past has implications for our understanding of Mars, the possibility of life there in the past or even today, and any future exploration – whether robotic or in person.
“In situ identification of such environments indicates a more active Amazonian surface hydrosphere for Mars than previously thought. The Zhurong landing site (and the northern lowlands) may contain a considerable amount of water accessible as hydrated minerals and possibly ground ice for in situ resource utilization for future human exploration of Mars,” the authors wrote in the paper.
Mars continues to keep the secrets of its water-rich past close to its chest, but slowly and surely we are getting better at uncovering them.