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What We Know About China’s Mars Rover Zhurong Touchdown

The United States now has company on Mars.

A Chinese spaceship descended through the thin Martian atmosphere and landed safely on a large plain on Saturday morning, state media reported, and achieved an achievement only two other nations had previously achieved. (In the United States, it was Friday – 7:18 p.m. East Coast time – when the spaceship touched down.)

The landing follows China’s launch last month of the core module of a new orbiting space station and a successful mission in December that collected nearly four pounds of stones and earth from the moon and returned it to earth. In the next month, the country’s space program plans to send three astronauts back into space to establish a regular Chinese presence in Earth orbit.

Just when China’s space program arrived on Mars in February and orbited the planet, it confirmed its place among the leading agencies exploring the solar system. Now that it has made a landing – with the use of a rover pending – it has established itself as the main competitor in a new era of space competition.

The Global Times, a Communist Party-controlled newspaper, said the mission “spectacularly captured a new important milestone” with its landing.

Thomas Zurbuchen, NASA Assistant Administrator for Science, congratulated the Chinese. “Together with the global scientific community, I look forward to the important contributions this mission will make to human understanding of the Red Planet,” he wrote on Twitter.

As of Friday, the Chinese space agency had said little about its plans for the landing, in line with its usual operational secrecy. However, news of the impending landing spread across social media and official news reports, signaling that the landing was imminent.

“Stargazers from around the world have now turned back to Mars,” wrote the Global Times. A user of Weibo, the popular social media platform, republished the nine photos that Tianwen had broadcast so far.

In a virtual conference organized by Weibo on Friday, several scientists discussed the reasons for exploring Mars. One said that the evolution of the planet could teach lessons for changes on earth.

“The purpose is to better protect our earth itself,” Jiao Weixin, professor of geophysics at Peking University, told the forum. “I think this is the most basic purpose of our space exploration.”

The Chinese Space Agency also highlighted international collaboration on the Tianwen-1 mission, including contributions from the European Space Agency, Argentina, France and Austria.

The Tianwen-1 mission launched from Earth last July and aimed to use the time window every two years when Mars and Earth are closest together on their journeys around the Sun.

The mission consists of an orbiter, a lander and a rover.

The Tianwen-1 orbiter entered orbit on February 10th. since then it has been circling at a safe distance and preparing to attempt to land.

The unnamed landing craft carries a rover named after a fire god Zhurong in Chinese folk tales. That name knocked out nine other semi-finalists announced in February.

The mass of Zhurong is about 240 kilograms, or about 530 pounds. This is slightly more powerful than the Spirit and Opportunity rovers that NASA landed on Mars in 2004, but only about a quarter of the mass of the two currently operating NASA Mars rovers Curiosity and Perseverance.

It will be days after touchdown for the rover to roll off the lander. Like Spirit and Opportunity, Zhurong is powered by solar panels. For endurance and curiosity, nuclear batteries convert the heat released by the decay of radioactive plutonium into electricity.

The rover’s seven instruments include cameras, ground penetrating radar, magnetic field detector and weather station.

This was not China’s first attempt at a mission to Mars. That was Yinghuo-1, which failed almost 10 years ago, though through no fault of the country’s own. This spaceship burned down in the Earth’s atmosphere when the Russian missile it was traveling on failed in flight.

It landed in Utopia Planitia or Nowhere Land Plain, a huge basin in the northern hemisphere that was most likely destroyed by a meteor strike. The same region was visited by NASA’s Viking 2 lander in 1976.

The plains are part of the northern lowlands of Mars. If there was once abundant water on the red planet a few billion years ago, this region might have been underwater, part of an ocean that covers the upper part of the planet. The Planitia utopia is among the features proposed as two types of coastline that are remnants of such early Martian seas.

Some of the water from this hypothetical ocean could once have seeped underground and is still frozen there today. In 2016, scientists using a radar instrument on NASA’s Mars Reconnaissance Orbiter concluded that there was actually a lot of ice there – as much water as Lake Superior, which stretches over an area larger than New Mexico is.

One goal of the Tianwen-1 mission is to better understand the distribution of ice in this region that future human colonists on Mars could feed on.

Landing on the red planet is dangerous – NASA engineers describe it as seven minutes of terror when its rovers, most recently Perseverance, arrive.

Since Tianwen-1 was already in orbit around Mars, its entry speed was not quite as fast as that of Perseverance. China’s lander needed a little extra terror – nine minutes – to land, the Global Times reported on Friday, citing experts. The probe also worked alone, as the signal transmission between Mars and Earth currently takes 17 minutes and 42 seconds.

Spaceships are descending towards Mars at high speed, and the thin atmosphere is insufficient to slow down the journey to the ground. The shock waves of the air compressed by the speed capsule generate extreme heat that must be absorbed or dissipated. A number of Soviet, NASA and European missions have crashed.

Only NASA has reached the surface of Mars intact more than once. The landings of its largest rovers, Curiosity and Perseverance, have relied on parachutes to slow the spaceship, shields to divert heat from atmospheric friction, and intricate systems known as sky cranes. These were basically rocket-propelled jetpacks that carried the rovers under them and lowered them to the surface with cables before safely flying away from the landing zone.

The Global Times reported that the Tianwen-1 probe lowered its altitude from its park orbit before its lander-rover combination with the orbiter separated at around 4 p.m. Friday Eastern time. (It was 4 a.m. on Saturday in China.)

The orbiter then rose and returned to its park orbit about half an hour after it split up to provide relay communications for the landing craft combination, the Chinese space agency told the Global Times. The lander-rover combination orbited Mars for three hours before entering the Martian atmosphere on the way to landing.

For the Tianwen mission, a cone-shaped entry capsule carried the lander and rover through the atmosphere. A heat shield protected the spaceship from overheated gases as it sped through the atmosphere. Then the friction of the thin Martian air helped slow it down – by about 90 percent, Tan Zhiyun, designer at the China Academy of Space Technology, told The Global Times.

The heat shield was thrown off at a lower altitude. In the next step, the parachute and the upper nose-shaped piece were thrown away. The four-legged lander fired a rocket engine and was similar in design to the Chang’e-3 and Chang’e-4 lunar lander. He hovered briefly as he searched for a safe place and descended to a safe landing.

China is on the other side of the moon with a robotic rover and recently put a large chunk of its next long-term space station into orbit. The country’s space program has many other goals as well. Read more about China’s space exploration plans here:

In the past few weeks, Ingenuity, an experimental helicopter built by NASA, has made its first flights on the surface of Mars. The little rotorcraft was supposed to show that it was possible for something like a helicopter or an airplane to fly in the thin Martian atmosphere.

Earlier this week, the spacecraft released images of hydrogen atoms surrounding Mars at different times of the day. Such studies can help scientists on Earth better understand how gases circulate on Mars and eventually escape the planet.

Claire Fu contributed to the research.

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