The surface of Mars is, at first glance, a rather desolate place. The soil is many times drier than the driest desert on planet Earth, the temperature fluctuates from one extreme to the other, and the air is incredibly diluted and poisonous.

Yet there is plenty of evidence that the planet was once much warmer and wetter, with abundant flowing and standing water on its surface. Over time, Mars’ atmosphere gradually disappeared, while much of this water was lost into space, and what remained concentrated around the poles, mostly as glacial ice and permafrost.

Over the years, space agencies have sent robotic landers, rovers, orbiters, and spacecraft to Mars to learn more about when this transition occurred and how long it took. Liquid water may have appeared on the Martian surface later than previously thought, according to the China Tianwen-1 mission, which includes the Zhurong rover.

According to new research from the Chinese Academy of Sciences (CAS), the Zhurong rover observed salt-rich sand dunes in the Utopia Planitia region that showed cracks and crusts several hundreds of thousands of years ago, indicating possible water presence.

The research team was jointly led by Xiaoguang Qin and Xu Wang of the Cenozoic Geology and Environment Main Laboratory at the Institute of Geology and Geophysics; and Xin Ren and Jianjun Liu from the Key Laboratory for Lunar and Deep Space Exploration (part of the National Astronomical Observatory).

They were joined by many additional researchers from their own institutions, the College of Earth and Planetary Sciences and the Institute of Atmospheric Physics. Their findings are described in a paper published April 28 in Science Advances.

As they explain, the Zhurong rover observed interesting features on the surface of the Barchan Dunes in Utopia Planitia, a vast plain and largest impact basin in the Solar System. These dunes are a characteristic feature of the northern hemisphere of Mars, similar to the dunes seen in deserts all over the Earth.

These are the result of strong winds depositing crescent-shaped sand with the curved side downwind. Observing the dune field in the southern part of the Utopia Plain, Zhurong noticed crusts, fissures, aggregates and bright polygonal ridges.

The team concluded that these elements consist of small pockets of water made up of melting frost or snow mixed with mineral salts. After sublimation of water in the Martian atmosphere, depressions and protrusions remained, as well as pieces of hard crust and loose material. Like other features formed in the presence of water, they were preserved by the extremely cold and dry atmosphere of Mars.

But unlike other objects that are hundreds of epochs or billions of years old, the team believes these objects formed between 1.4 million and 400,000 years ago (perhaps even more recently).

As they explain in their paper, the team was able to rule out the possibility that frozen carbon dioxide (“dry ice”) and wind were responsible:

“Instead, salt water from melting frost/snow is the most likely cause. This discovery sheds light on the more humid conditions of the modern Martian climate and provides important clues for future research missions to look for signs of life that exists, particularly at low latitudes. has a surface temperature.”

At that time, the Martian environment was pretty much the same as today (i.e. extremely cold and dry). Therefore, these findings show that a hydrological cycle existed on Mars very recently, much earlier than previously thought.

The team also ran a computer simulation and combined it with observations made by other robotic missions. This suggests that conditions for frost and ice formation may be favorable at certain times of the year in other parts of Mars, leading to similar characteristics elsewhere.

This is consistent with observations made by robotic missions since NASA’s Viking 1 and 2 missions discovered Mars in the late 1970s. But scientists have a general consensus that morning frosts occur only in certain places and under very limited conditions.

This discovery suggests that there may be occasional spots of liquid water in other parts of Mars today, but the amount may be very small. According to the authors of the study:

“This discovery sheds light on the more humid conditions of the modern Martian climate and provides important clues for future exploration missions that will look for signs of life, particularly in lower latitudes with relatively higher and more favorable surface temperatures.”

The discovery may also indicate the existence of small patches of fertile land where microbial life can still exist today. Of course, more research is needed before any of these can be said for sure. These studies may have to await future missions, as the rover has not yet awakened from hibernation.

According to Zhang Rongqiao, lead designer of Tianwen-1, this is likely due to dust buildup on the rover’s solar cells. As with NASA’s Insight and Opportunity missions, this could prevent the mission from running again.

After landing from the Tianwen-1 lander on May 22, 2021, the rover spent nearly a year exploring the Martian surface before entering hibernation on May 20, 2022. Designed to operate only 90 Mars days or 93 Earth days, the rover far exceeded its intended service life.

As of May 5, 2022, Zhurong also managed to cross the surface by 1,921 meters. If the China National Space Agency was unable to save the rover in the near future and decided to end the mission, Zhurong could not have chosen a deeper exploration! This article was originally published on: Universe Today.