Despite its increasingly likely death, the Chinese rover Zhurong still surprises. A new study indicates that he may have discovered traces of liquid water on the surface of Mars. A phenomenon that could have taken place relatively recently.
Zhurong may be on the verge of death, but the Chinese rover which began its exploration of the surface of Mars two years ago is being talked about again. Latest find: he would have discovered what looks like traces of relatively recent water on the ground.
A study published on April 28, 2023, in the journal Science Advances, looks back on the detection by the rover of strange shapes on the ground, in the region of Utopia Planitia. Cracks that might have been left there by liquid water. The Chinese authors write: “These features were formed between 1.4 million and 400,000 years ago. We don’t think they could have been created by wind and CO2, but saltwater involvement is most likely the main cause“.
“It’s interesting because we’ve never seen such shapes,” says Nicolas Mangold, a geologist specializing in Mars, who was not involved in the study. It looks a bit like what the Phoenix probe that arrived in 2008 saw, but it was much further north, near the polar ice cap. Here is a very different area.
Utopia Planitia, terra incognita
Utopia Planitia has been very little explored in the past. Zhurong is the only rover to roam this huge, relatively young plain, and while climate models predicted that water may have existed there, having real tracks in situ is much more valuable.
The authors of the study remain cautious and specify that these forms may be due to something other than water, but the other hypotheses are even more improbable. “It could be traces of frost, considers Nicolas Mangold, but it would be really surprising to have some at these latitudes“.
Images were taken by Zhurong of rock agglomerates. // Source: Study
Despite everything, the authors think of carrying out other more thorough studies to eliminate all the assumptions. The question of the existence of water on the surface of Mars in the most recent period is central. If the proofs of a humid past of the red planet are numerous, the certainty is much less strong with regard to the Amazonian. During this period, which began just over 3 billion years ago, Mars lost its magnetic field and cooled and dried up considerably. Some hypotheses evoke remains of liquid water on the surface, but in small quantities and in certain very specific circumstances. This is why Zhurong’s research into a Utopia Planitia formed during this period is important.
“Humidity, not much more”
Moreover, the study affirms that if these traces are due to water, it is extremely salty water, close to brine. Salt is useful in lowering the melting point, allowing liquid water to exist even at temperatures far below 0°.
“If this water were found on Earth, we would have a hard time considering it as liquid water,” explains Nicolas Mangold. “It is brine in very small quantities, which could, at the limit, be defined as humidity, but little more“.
Not very appetizing, but the authors assure that if confirmed, it could change the way we search for traces of life on Mars. The existence of this “late” brine could mean that favorable conditions for creating life have existed, and persisted and that this is an avenue to be explored. They envision, for example, dedicated studies of terrestrial microbes that survive in extremely salty environments, to see if equivalents can be found on Mars.
Projects that make Nicolas Mangold a little skeptical: “This type of brine can be found on Earth in Antarctica, and in the Atacama Desert, in Chile. But, if life can thrive there, it is above all because there is life everywhere else on Earth. It’s not a very hospitable environment, although we obviously lack the data to be sure“.
Zhurong, seen from the sky of Mars in June 2021. // Source: NASA/JPL/UArizona
In other words, the hypothesis would be that life existed on Mars. However, when the climate became drier and colder, other forms would have adapted to these pockets of salty liquid water to thrive in a world that had become otherwise uninhabitable. An interesting hypothesis to explore, but its current evidence remains quite limited.
The authors of the study conclude by saying: “Our findings are useful clues to prepare future exploration strategies for Mars rovers“. This future will probably be without Zhurong since the Chinese rover is probably coming to the end of its life. NASA probes have seen him motionless for months, and he is not giving any more news. The Chinese head of the mission explained on April 25 that dust buildup on the solar panels was likely the cause of the shutdown, but there was not enough data to know if he would still be able to wake up and activate his cleaning of the panels. He could have until July 12 to do so. Beyond that, the summer solstice will have passed and the sunshine will remain too low to hope for a return.
Whatever the outcome, Zhurong will have brought us new knowledge on this area so little explored before him.