Don’t you hate it when you think you’re underground, but you're actually several kilometers in the air?
Sure, probably not a regular occurrence for most of us – but that’s probably what happened to ESA’s Schiaparelli ExoMars lander last month, according to a statement from the agency after studying available data.
Schiaparelli was supposed to pass through the atmosphere of Mars, deploying its parachute and jettisoning its heat shield, before using thrusters to touch down on the surface on October 19.
Everything seemed to be looking good. The lander deployed its parachute correctly 12 kilometers (7.5 miles) above the surface at a speed of 1,730 kilometers per hour (1,075 miles per hour), and released its heatshield at 7.8 kilometers (4.9 miles).
But then things went wrong. An instrument that was measuring the rotation of the lander, the Inertial Measurement Unit (IMU), hit a maximum reading and recorded a rotation 1 second longer than expected.
This glitch was enough to cause the navigation systems to go haywire. Due to the “erroneous information”, in ESA’s words, the lander suddenly thought it was below ground level – when it was actually still 3.7 kilometers (2.3 miles) above the ground.
The result was that it immediately released its parachute and backshell (the casing on top of the lander), fired its thrusters, and turned on its ground instruments – thinking it had landed. Instead, it went into freefall, ultimately crashing into the surface at more than 300 km/h (186 mph), where it was instantly destroyed.
This image shows the remains of Schiaparelli on the surface of Mars. NASA/JPL-Caltech/University of Arizona