China’s first interplanetary spacecraft has entered orbit around Mars, a major milestone for the country’s space program. That sets the mission up for its next step: landing a rover on the red planet in May.
Tianwen-1, as the mission is called, means “questions to heaven.” It aims to be the first Mars mission to send a spacecraft into orbit, drop a landing platform onto the Martian surface, and deploy a rover all in one expedition. On Wednesday, the five-ton probe carrying all the components fired its thrusters for about 15 minutes, slowing its approach as it sped toward Mars and allowing the planet’s gravity to pull it into orbit, according to Chinese state media.
The entire operation was autonomous — the communications delay at such a distance is too long for mission controllers to give the spacecraft instructions in real time. Had this crucial step failed, the spacecraft could have crashed into Mars or careened past the planet into deep space.
If Tianwen-1 successfully sets its lander down on Martian terrain, that will mark the first non-NASA Mars landing since the Soviet Union’s rover touched down in 1971. The mission is also intended to help China prepare for a future attempt to return Martian rocks or dirt to Earth in the late 2020s.
China’s last attempt to launch its first interplanetary mission involved a simple Mars orbiter. But the Russian spacecraft meant to carry it through space stalled in Earth’s orbit in 2011 and never left.
This time, China launched its own vehicle, aboard a Long March 5 rocket. It lifted off from the Wenchang Space Launch Center on July 23. That was one of a trio of Mars launches that occurred around the same time to take advantage of a window in which Earth and Mars pass close together, making the voyage shorter and cheaper. Seven months later, the Tianwen-1 spacecraft has completed its 300-million-mile journey.
The United Arab Emirates’ Hope probe beat Tianwen-1 to Mars — it fell into orbit around the red planet on Tuesday. That made the UAE the fifth nation ever to reach Mars, and China the sixth. The third Mars mission of the month, NASA’s Perseverance rover, is set to land there on February 18.
As Tianwen-1 circles the planet over the next three months, it will scope out its own landing site in Utopia Planitia — a vast field of ancient volcanic rock that could conceal liquid water deep below the surface. NASA’s Mars Reconnaissance Orbiter detected an underground deposit of ice there that may hold as much water as Lake Superior.
Such underground reservoirs could be the remnants of an era billions of years ago, in which rivers flowed on Mars, supported by a much thicker and more protective atmosphere than the one that exists today. During that time, Mars somewhat resembled Earth, and scientists think it may have hosted alien microbial life. Any underground pockets of water are likely to be shielded from the sun’s unfiltered radiation and the vacuum of space, so might still harbor such species — if they exist.
Knowing where to find water ice is also crucial for any future astronauts headed to Mars. Such interplanetary human missions will need water both to drink and to break down into oxygen and hydrogen — for breathing and rocket propellant.
The Tianwen-1 rover is poised to become the first robot on Mars’ surface to seek out these water pockets, and the first to explore Utopia Planitia. But first it has to land safely.
7 minutes of terror and 2 years in orbit
Half of all the spacecraft humanity has tried to land on Mars never made it. Tianwen-1 will take on those odds in May, when the orbiter is supposed to drop the mission’s lander-rover combo down to the planet’s surface. It will be a major test of China’s aerospace engineering.
Officials and engineers often call the entry, descent, and landing phase of a Mars mission “seven minutes of terror.” That’s because the feat requires a capsule that can protect a lander or rover (or both in China’s case) as it plummets through the Martian atmosphere at temperatures exceeding 2,000 degrees Fahrenheit. A supersonic parachute is needed to slow the fall, along with a set of thrusters to navigate along the way.
If that descent goes smoothly, the Tianwen-1 mission’s lander will deploy a two-track ramp on which the rover will roll down onto Martian soil. The rover is set to explore the area for 90 Martian days, according to a journal article by scientists on the Tianwen-1 team.
Meanwhile, the orbiter will continue circling the red planet for one Martian year (two Earths years), relaying data to Earth and taking photos. Its main goal, according to the scientists, is to “perform a global and extensive survey of the entire planet.”
This will involve charting Mars’ geology, surveying its climate, and measuring its electromagnetic and gravitational fields.