China’s Zhurong rover reveals complex layers under Mars surface

Beijing, March 1

The radars on China's Martian rover Zhurong have detected shallow impact craters and other geologic structures 5 metres beneath the surface of Mars.

Much of the Martian surface is covered with a weathering layer (regolith or soil) produced by long-term surface processes such as impact gardening, eolian erosion, water weathering, and glacial modifications.

The Zhurong rover uses two radar frequencies -- a lower frequency that reaches deeper (about 80 metres) with less detail, and a higher frequency, which shows more detailed features but only reaches about 4.5 metres down.

The team of researchers from Macau University of Science and Technology, China, employed the Mars Rover Penetrating Radar (RoPeR) with high frequency to image the subsurface of Mars.

The researchers saw several curving and dipping underground structures in the Martian soil that they identify as buried impact craters, as well as other sloping features with less certain origins.

They did not see any evidence of water or ice in the top five metres of soil.

Radar images of the deeper structures revealed layers of sediment left by episodes of flooding and deposition in the past, but also found no evidence of water in the present day. This does not rule out the possibility of water deeper than the eighty metres imaged with the radar, the team said in a paper published in the journal Geology.

"We found a lot of dunes on the surface at the landing site, so maybe this crater was quickly buried by the sand and then this cover reduced space weathering, so we can see the full shape of these craters' walls," said the study's lead author Yi Xu from the varsity.

The researchers hope that imaging the subsurface of Mars will help to shed light on the planet's geologic history, previous climate conditions, and any water or ice the planet may host now or in the past.

The rover, named Zhurong after the god of fire in Chinese mythology, was sent to Mars as part of China's Tianwen-1 mission. Launched in July 2020, the rover landed on the surface on May 15, 2021.

It was sent to a large plain in the northern hemisphere of Mars named Utopia Planitia, near the boundary between the lowlands where it landed and the highlands to the south.

Meanwhile, after completing two years in space, the rover reportedly entered hibernation on May 18, last year, due to severe winter weather.

The Zhurong rover was expected to wake up in December, but China has remained silent on the status of the rover, Space.com reported.

The rover does not carry a radioisotope heater unit, like other rovers including China's Yutu moon explorers.

It has a pair of "windows" allowing a chemical called n-undecane to store heat energy.

"Dust storms in Utopia Planitia may have impacted the rover's ability to generate heat and light. This could potentially be the issue explaining Zhurong's silence," the report said.

--IANS