China lands rover on Mars

AT 17:17 GMT May 14 Tianwen-1, a Chinese mission that had been in orbit around Mars since Feb. 10, made a subtle adjustment to its trajectory, which put it on track to reach the planet’s surface six hours later. After three hours, however, it broke in two. One part readjusted its trajectory in order to fly over the planet and stay in orbit. The other, a sealed hull with a heat shield on the outside and valuable cargo inside, tumbled to the surface at 17,000 km / h.

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It entered the atmosphere about 125 km above the ground, blazing across the alien sky like a meteor. After the friction with the air had removed most of its kinetic energy, it deployed a parachute. The hull split open, revealing a four-legged landing pad, rocket motor, and six-wheeled rover strapped to its top. The engine caught fire. When the platform had only 100 yards to go, it paused briefly, hovering as its sensors searched for obstacles that would prevent a safe landing. Then he lay down in a cloud of red dust over Utopia Planitia, one of the great flat plains in the northern hemisphere of Mars.

To land

Entry, descent and landing (EDL) is historically the riskiest part of any mission to the Martian surface. Every engineering system must work perfectly. And everything must be done entirely on the basis of data processing and programming on board, without the supervision of any human being. Mars is currently 320 meters from Earth, which means radio signals between planets take 18 minutes to travel each way. By the time the engineers, researchers and bigwigs gathered at the Beijing Aerospace Control Center knew for sure that the spacecraft was entering the atmosphere, the dust had long since settled.

Once news of his arrival reached mission control, Chinese media wasted little time in announcing the triumph to an awakened nation that, for the most part, was blissfully unaware of the drama unfolding in the heavens. Aware of EDLrisks, authorities had given little notice of the attempted landing. Details of Tianwen-1Orbital maneuvers were developed by amateurs monitoring Chinese telemetry using a radio antenna from the Apollo era in Germany.

The announcement underscored not only the disembarkation itself, but the complete success of the mission it capped. Orbiting and landing on a planet China has never visited before, Tianwen-1 had become the most successful first Mars mission in history. America only landed on Mars five years after it was first put into orbit.

That said, the first American orbiter and its next Viking landers made their trips in the 1970s. The Soviet Union also made a successful landing. But the European Space Agency (ESA) failed twice in this task, in 2003 and 2016 – the second of such attempts to partner with the Russian space agency Roscosmos. Getting it right the first time is definitely a success, even half a century later. It is moreover one achievement among many others. In January 2019, China became the first country to install a rover on the other side of the moon. And last month he launched the first part of a new space station. A second part is planned shortly.

However, China still has a long way to go. The capabilities of Perseverance, the one-ton lander that the United States National Aeronautics and Space Administration, NASA, deposited at a precisely chosen place in the crater of Jezero on February 18, much higher than those of the Chinese rover, Zhurong, which is a quarter of the size. And Perseverance benefits from an orbital infrastructure established in the form of the Mars Relay Network, five satellites (three American, two European) capable of returning high bandwidth data to Earth. One of the reasons given for ZhurongThe failure to return photos until May 19 was that the Tianwen-1 the orbiter had to refine its orbit again in order to transmit messages.

When Zhurong does not descend from its platform and head for the plain, attention will be focused on data from its ground penetrating radar, which is designed to be able to detect ice at depths of up to 100 meters . The distribution of ice is of great interest to those who study Mars, defining as it does the limits of the planet’s potential habitability both in its less arid past and, perhaps, in its inhabited future. by the man.

The Mars Groundwater Ice Mapping Project (SWIM), an attempt to synthesize the results of many different approaches to the question, suggests that when Viking-2 Scratched the surface of its landing site in another part of Utopia Planitia in the 1970s, its robotic arm may have been inches from the permafrost. But it was at 48 ° N. ZhurongThe landing site, at 25 ° N, is in the Martian tropics, where subterranean ice is much less likely to persist near the surface. The improbability, however, is not impossible – and that would make any icy discovery even more exciting.

Wild rovers

Until what point Zhurong will be able to go in search of ice is hard to say. It is similar in size and design to Mind and Opportunity, two American rovers landed in 2004, and like them, he has an official life expectancy of 90 sols (one sol is a Martian day, 40 minutes longer than a terrestrial day). Mind lasted six years, Opportunity 14, on which he traveled 45 km. If Chinese engineering is of a similar caliber and its operational teams are just as skilled, Zhurong may still have a long way to go.

It could even last until the next milestone in the exploration of Mars: the return of the samples to Earth. It’s a goal NASA has been talking about it for decades and now intends to realize it. Part of PerseveranceThe latter’s mission is to collect a cache of samples to be picked up later by a seal NASA-ESA mission. In a few years, according to the plan, America will unload a package near this cache. This will contain both a small European rover to retrieve the samples and a rocket capable of putting them into orbit, from where another European spacecraft will pick them up and bring them back to Earth. It is the most ambitious planetary science mission currently in planning.

China is also planning a sample return mission to be launched towards the end of the decade. He showed some of the abilities required for this by returning samples from the Moon last year. If he just brought back any old specimen that could be hit from a lander with a rocket on board, this mission could presumably be accomplished at about the same time as the more sophisticated one. NASA-ESA try. It would really be an interesting space race.

This article appeared in the Science and Technology section of the print edition under the title “Welcome to Utopia”


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