Landing on the red planet is perilous — NASA engineers refer to it as seven minutes of terror when its rovers, most recently Perseverance, arrive.
Because Tianwen-1 was already in orbit around Mars, its incoming speed was not quite as fast as Perseverance’s. Thus, China’s lander required a bit of extra terror — nine minutes — for the landing, The Global Times, a newspaper controlled by the Communist Party, reported on Friday, citing experts. The probe was also operating on its own, as signals currently take 17 minutes 42 seconds to travel between Mars and Earth.
Spacecraft descend toward Mars at a high speed, and the thin atmosphere does not do enough to slow the trip to the ground. The shock waves of air compressed by the speeding 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 spacecraft, shields to dissipate the heat from atmospheric friction and intricate systems called sky cranes. These were basically rocket-powered jetpacks carrying the rovers beneath them and lowering them to the surface on cables before flying safely away from the landing zone.
“For our country’s first Mars exploration mission, we didn’t have first hand data about the environment on Mars, especially the atmosphere,” Chen Baichao, a senior designer for the mission, said in remarks reported by The Paper, a Shanghai-based news site. “So it was tantamount to us entering a completely unknown environment, and you can imagine how difficult that is.”
The Global Times reported that Tianwen-1 probe lowered its altitude from its parking orbit before its lander-rover combination separated with the orbiter at around 4 p.m. Friday Eastern time. (In China it was 4 a.m. Saturday.)
The orbiter then rose and returned to its parking orbit about half an hour after the separation, to provide relay communication for the landing craft combo, the Chinese space agency told The Global Times. The lander-rover combination circled Mars for another three hours before its entry into the Mars atmosphere en route to landing.