China's Tianwen-1 enters Mars orbit
February 10, 2021
Space missions are never easy, whether you're sending astronauts a mere 400 kilometers (248 miles) up to the International Space Station, or communications satellites a few thousand kilometers up. Things can and do go wrong.
Mars missions are the next level. The planet is farther away, and harder to get to as a result.
But, a day after the UAE's Emirates Mars Mission successfully delivered its Hope probe into the orbit of Mars, China has also arrived.
The Tianwen-1 spacecraft began the orbit Mars on Wednesday, seven months after launching from Earth and traveling 450 million kilometers.
As with the UAE's Hope probe, the Tianwen-1 spacecraft conducted a "braking" operation to decelerate its speed so that it could be captured by Mars' gravity and avoid overshooting its target or crashing into it.
So it's perhaps with good reason that China did not announce an exact arrival time, or stream the operation live as the UAE did on Tuesday.
As the AP news agency put it ahead of the operation: "Chinese authorities, always cautious about possible failure, have not announced a planned arrival time."
Indeed, all they said in advance was that the spacecraft was on track to arrive before the Lunar New Year on Friday.
On the previous Friday, February 5, Tianwen-1 performed a fourth "orbital correction" maneuver. That was necessary to make sure that the spacecraft would be ready for its arrival in orbit, according to the China National Space Administration.
Tianwen-1's Mars mission
The goal of Tianwen-1 is to survey the atmosphere from orbit over a two-year period.
About 4 billion years ago, the atmosphere of Mars changed and liquid water evaporated. But scientists don't know why. There may be deposits of water underground, known as subsurface water.
So the mission is intended to go deeper than the Hope probe will. It is scheduled to land a rover on the surface of Mars in May.
A precise location has not been named, but the mission controllers have been looking at the southern part of a region called Utopia Planitia.
The solar-powered rover is expected to operate for a few months, looking for subsurface water — signs of life below the surface of the planet.
It will be roving Mars along with American landers, such as NASA's Mars 2020 Perseverance rover and its accompanying Ingenuity helicopter.
Instruments on the probe and rover
Tianwen-1's orbiter, or probe, is carrying 13 "payloads." A payload can be a communications or Earth observation satellite, but in this case the payload is the mission's instruments.
For instance, there's a remote sensing camera and a ground penetrating radar.
Once the lander and rover detach from the probe and land on the surface of Mars, additional instruments include a subsurface penetrating radar (SPR).
As the name suggests, the SPR's main scientific objective is to investigate the Martian soil below the surface of the planet to determine its thickness and makeup.
The rover weighs about 200 kilograms (440 pounds). As it will be powered by solar panels, power would be impeded by a landing in the planet's northern hemisphere — landing at the equator is better for solar power.
It will investigate the ground with radar, perform chemical analyses on the soil, and look for biomolecules and biosignatures.
Race to return Martian rock
It's been reported that if it succeeds in landing a rover on Mars, China will become only the second nation to do so. But that's not strictly true.
It is true that many have tried and failed, including European and Japanese missions. It is also true that the United States is the only country to have a relatively consistent track record of landing rovers on Mars, independently.
But the Americans do also collaborate on missions. The InSight mission, for instance, is an in-situ laboratory investigating seismic activity on Mars. And that would not have been possible without European engineering.
NASA is also working with the European Space Agency on developing sample return missions to bring the first pristine samples from Mars back to Earth. The US Mars 2020 Perseverance rover, which is due to land on February 18, is seen as a first step towards that goal.
But the Americans and Europeans will have to hurry, because they are not alone now. China sees its own mission, Tianwen-1, as a step towards future missions that would also bring back rock and soil samples from Mars to Earth.