The map recently appeared in a presentation at the United Nations Committee on the Peaceful Uses of Outer Space (COPUOS) in June, and again in a presentation by mission engineers at the International Astronautical Congress (IAC) in Germany last month.

As this is China’s first independent interplanetary mission, teams will need to succeed on a range of technological challenges including orbital insertion and landing. The country recently made progress on that front with successful supersonic parachute tests and tests of a subsurface detection radar from a hot air balloon in October (link in Chinese).

Chinese media reports from early September said Tianying-6 sounding rockets were launched in western China to send a full-scale supersonic parachute to altitudes between 44 and 54 kilometers, simulating travel through the tenuous Martian atmosphere. The reports state the parachute opened successfully, providing valuable aerodynamic data and verifying subsystems. Similar tests were carried out by NASA on 7 September 2018 from Wallops Island, Virginia, for its own 2020 rover mission.

First Mars EDL attempt

According to a paper by a team from the China Academy of Space Technology (CAST) presented at the Global Space Exploration Conference in Beijing in 2017, landing site selection has been a complex process in which flight system engineering constraints are balanced against science goals while still allowing the project's science objectives to be met.

The two demarcated areas are in relatively low-lying regions which offer advantages to first-time Mars entry, descent and landing (EDL) attempts, says Mason Peck, an associate professor at Cornell University and former NASA chief technologist.

“The atmosphere of Mars is really inconvenient. It’s too thick to ignore—so, aerothermal heating is important—but too rarefied to offer an easy descent by parachute. So, the lower the elevation, the more atmosphere the spacecraft encounters on its way to the surface, and, therefore, it can decelerate more easily,” Peck says. “If one is unsure of one’s decelerator technology, this is the best-odds approach.”

The landing will involve the use of blunt body aerodynamics, deployment of a supersonic parachute and powered descent to safely set the rover down on Mars. Part of the team that developed the Chang’e-3 lunar lander and rover, which successfully soft-landed on the Moon’s Mare Imbrium region in late 2013, is working on the mission, though Mars presents different and greater challenges: notably remoteness, more gravity, the presence of a thin atmosphere and less solar energy reaching the planet.

“It’s all very hard,” says Peck. “The smallest errors in orbit maneuvers or failure to correctly model the atmosphere can have catastrophic consequences.” To date, about half of Mars missions have failed, although NASA has a very good track record.

“The EDL sequence carries a lot of risk. Many technologies have to perform perfectly, for the first time: the aeroshell/heat shield, the aerodynamic decelerator (or parachute(s)), position and velocity measurement relative to the ground, and the landing subsystem,” Peck says. “Getting any one of these right is a remarkable technical achievement. Getting these all right is what’s necessary to land on Mars.”