The landing is a devilishly difficult feat. The landing capsule has to batter its way through the atmosphere. It will fly through the Martian air at an initial speed of 12,300 mph, and it must hit the atmosphere at an angle of precisely 12 degrees. Any shallower, and the probe will bounce off into deep space. Any steeper, and the probe will burn itself up in a spectacular and fiery death. The probe will first touch the atmosphere six minutes and 45 seconds before landing. During this phase, it will experience acceleration 12 times that of the Earth’s gravity. Were the probe a 150-pound human, during the flaming descent, it would weigh nearly a ton.