China’s Mars rover "Zhurong" has yet to drive off its lander and start exploring, but planetary geologists are already studying satellite images and geological maps to find landforms to study. Of particular interest is a possible mud volcano — a type of landform that no Mars rover has visited before.
“A number of teams will be trying to plan out the traverse — where you would go in what time frame, to accomplish as many goals as you can in a 90-day mission,” Joseph Michalski, a planetary scientist at the University of Hong Kong, explains in an interview with Nature.
The rover, named after a fire god of Chinese mythology, landed in a vast impact crater called Utopia Planitia about 1,800 kilometers northeast of NASA’s Perseverance rover, which landed in February. Utopia Planitia is also the landing site of the famous Viking-2 mission in 1976, the probe discovered (now contested) signs of microbial activity in the Martian soil. The first images taken by Zhurong were released yesterday, five days after its successful touchdown.
The lander has settled on a fairly smooth, sandy plain dotted with small craters, according to images of the region taken by spacecraft such as NASA’s Mars Odyssey, Mars Reconnaissance Orbiter and the Tianwen-1 orbiter. The site is close to the boundary between Mars’s northern lowlands and southern highlands, which might have been the shoreline for an ancient ocean that once covered the planet’s northern hemisphere.
Yuyan Zhao, a planetary geochemist at the Institute of Geochemistry, Chinese Academy of Sciences, in Guiyang, says that her priority is to study the composition of sediments for evidence they have been chemically altered, which would suggest that the area had once been under water.
Of great interest to scientists is a pitted, cone-shaped feature seen in images, about 3,000 meters northwest of Zhurong’s position: this could be a volcano formed from lava or mud. On Earth, mud volcanoes are associated with the degassing of sediments, squeezing water and mud out of the ground. Still active mud volcanoes on Mars might help to explain puzzlingly large quantities of methane that had been previously detected in the Martian atmosphere, with methane concentrations fluctuating during a Martian year. Terrestrial mud volcanoes are also habitats for bacteria, so there is even (a remote) possibility to discover signs of life in volcanic deposits.
The actual mission’s goal is to cover a distance of several hundred meters over the next 90 Martian days, so the presumed mud volcano is - at the moment - out of reach. The area Zhurong will study first features large sand dunes and boulders, possible ejecta from nearby impact craters.
The rover will analyse the chemical composition of rocks to infer their origin and use ground-penetrating radar to study structures below the surface. Remote sensing by satellites indicates there are significant deposits of ice stored underground.
In coming days, the China National Space Administration team will check that Zhurong’s instruments are functioning, before driving it down a ramp off the lander.