Phobos-Grunt reentry (January 2012)

On 15 January 2012, Russia's Phobos-Grunt spacecraft re-entered the atmosphere over the Pacific Ocean, ending a mission that had failed almost as soon as it began. Launched in November 2011 to return a sample from the Martian moon Phobos, the probe's propulsion system never fired to leave Earth orbit, leaving it stranded in low Earth orbit with its tanks full.

A toxic-fuel concern Because the spacecraft was loaded with the propellant intended for its journey to Mars — including hydrazine and nitrogen tetroxide — its uncontrolled re-entry drew added concern about hazardous materials surviving to the surface. In the end it came down over open ocean and no harm was reported.

A high-profile failure Phobos-Grunt was one of the most ambitious planetary missions of its time, and its loss in low Earth orbit — followed by a closely tracked, unpredictable re-entry — became a prominent example of how a launch-phase failure can turn an interplanetary spacecraft into a re-entry hazard.