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China’s Mars rover has amassed reams of novel geological data

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China’s Mars rover has amassed reams of novel geological data

The "Zhu Rong" Mars rover passing the parachute

In July Zhurong took this image of the landing site of the parachute and part of the capsule that had carried it safely to the surface.Credit: CNSA

More than 30 scientists across mainland China, Hong Kong and Macau are rushing to process data collected by China’s Mars rover, Zhurong, and by the nation’s Tianwen-1 spacecraft, which is in orbit around the planet. Several studies have trickled out, but researchers say that more are coming in the next weeks and months, offering insights on the climate, geology and history of Mars’s northern hemisphere.

Since September, the National Astronomical Observatories of the Chinese Academy of Sciences (NAOC), which has been receiving the data from space, has released nearly 200 gigabytes of information that was collected from eight instruments on the rover and orbiter between February and June. These instruments include cameras, a radar system, climate sensors and a laser spectrometer.

Some surface features, such as possible sedimentary material and potential mud volcanoes, hint at the historic flow of water, so scientists are looking for any clues that there was once water or ice below the surface. This is “of great scientific interest” as it might provide evidence of an ancient ocean, says Bo Wu, a planetary scientist at the Hong Kong Polytechnic University, who is analysing some of the data.

Tianwen-1 arrived at Mars in February. In May, it dropped a lander containing Zhurong onto a vast basin known as Utopia Planitia. The rover’s initial mission was intended to be only about three months long, but it has exceeded expectations. Over a period of four months, the rover travelled more than 1,000 metres, visiting features of interest and even investigating part of the capsule that brought it to the surface, along with the remains of the descent parachute.

Pause in communications

In September, Zhurong was powered down into hibernation by the China National Space Administration (CNSA) because Mars had passed behind the Sun, relative to Earth, meaning that communication was lost. However, in October it was powered up again, and has traversed another 200 metres in the direction of what may once may have been the coastline of an ancient ocean.

The month-long break offered mission scientists at research institutes across China a chance to start analysing data. Some researchers had already received images of Mars from the orbiter’s cameras in March, and the CNSA had previously shared with the public images and videos taken by the rover during its descent and from the surface. But now researchers are studying the much larger volume of data released in September.

This data set includes images from Zhurong’s navigation camera; climatic data on temperature, pressure and wind speed; information on the chemical composition of rocks, soil and sand dunes from a laser spectrometer; and clues from below the surface from its ground-penetrating radar.

Apart from the handful of images and videos released by the CNSA, few scientific insights about the mission have been released or published until now. Researchers say this is because it has taken time to process and clean up the data.

Doing this ensures that the data are reliable and removes noise produced by the instruments, says Lu Pan, a planetary scientist at the University of Copenhagen. The fact that this mission is China’s first to the surface of another planet might also have slowed things down compared with NASA’s recent Mars missions. “If this is the first time you do it, there’s a learning process,” she says.

David Flannery, an astrobiologist at Queensland University of Technology in Brisbane, Australia, who is in communication with scientists in China, says that the team’s approach to managing data could also have contributed to the delay in releasing new insights. With NASA’s Perseverance mission, which Flannery is involved in, each instrument on the rover is designed by a different team, which has exclusive access to data from that instrument for a few months before it becomes available to all.

But under the CNSA model, the data generated for all the instruments on Zhurong and Tianwen-1 are processed by the NAOC, before making the information available to multiple teams of scientists linked to the mission.

The parachute opening during landing

The CNSA released this image in July of the view from the lander up towards the parachute as it drifted down to the surface of Mars.Credit: CNSA

Speeding up the analysis

Two publications have already emerged. One study1, posted as a pre-print in late September, analysed images and information on friction that were gleaned from the movement of Zhurong’s wheels. The results show that regions of Mars that the rover trundled over have properties similar to those of compact, sandy soil on Earth.

The study “provides useful data about surface soil properties”, says Xiao Long, a planetary geologist at the China University of Geosciences in Wuhan. This might be helpful for understanding how soil and dust on the surface formed, says Long, who is also conducting his own analysis.

A second study2, published in August, used high-resolution images from the orbiter to pinpoint the rover’s precise coordinates on Mars. But researchers say that many more studies are expected soon, including some on the region’s topography.

So far, the data has been shared only with researchers directly involved with the mission, but Wu says that the NAOC will at some point release them to the public and the international community.

That could help to speed up the analysis. Scientists with more experience of Mars might be able to recognize features of interest and their significance more quickly, says Flannery. “Mars is peculiar in some ways, and geologists are only as good as the rocks they have seen in the past,” he adds.

Next phase of the mission

Zhurong will now continue to explore, potentially for years, as some of NASA’s Mars rovers have.

Tianwen-1 has also been busy. The spacecraft recently adjusted its orbit and switched from acting mainly as a communications relay between Zhurong and Earth to also conducting its own observations of Mars. Wenzhe Fa, a planetary scientist at Peking University, Beijing, who is analysing Zhurong’s radar data, says that on 11 November, the CNSA deployed and began to test the antenna for the orbiter’s radar.

Also earlier this month, the CNSA and the European Space Agency (ESA) trialled whether the ESA’s Mars Express orbiter could be used to relay Zhurong’s data to Earth — an exercise that Pan says is an “amazing step” towards increased international collaboration with China.

As Zhurong resumes its journey, Bo says that he and his team are providing “suggestions for future data collection” that take in surface features of particular scientific interest.

doi: https://doi.org/10.1038/d41586-021-03554-8

References

  1. 1.

    Ding, L. et al. Preprint at Research Square https://doi.org/10.21203/rs.3.rs-836162/v1 (2021).

  2. 2.

    Wan, W. et al. Remote Sens. 13, 3439 (2021).

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