Europe's pioneering spacecraft Rosetta headed for a crash landing Friday on the comet it has stalked for two years, a dramatic end to a 12-year odyssey to demystify our Solar System's origins.
Sent by ground controllers on a leisurely, 14-hour freefall, Rosetta was engaged in a last-gasp spurt of science-gathering on the 19-kilometre (12-mile) journey to its icy comet tomb.
"Next stop #67P!" the European Space Agency (ESA) tweeted late on Sept. 29, using a shortened version of Comet 67P/Churyumov-Gerasimenko's full name.
The craft was programmed to terminate its historic quest at about 1040 GMT on Sept. 30, joining long-spent robot lander Philae on the comet for a never-ending journey around the Sun.
With the comet zipping through space at a speed of over 14 kilometres (nine miles) per second, Rosetta was programmed to make a "controlled impact" at human walking speed, about 90 cm (35 inches) per second.
Mission scientists expect it will bounce and tumble about before settling — but the craft's exact fate will never be known as it was instructed to switch off on impact.
Rosetta was never designed to land.
Confirmation of the mission's end is expected in Darmstadt around 1120 GMT when Rosetta's signal, which takes 40 minutes to travel, vanishes from ground controllers' computer screens.
But before then, it is expected to upload valuable data as it sniffs the comet's gassy coma, or halo, measures its temperature and gravity, and takes pictures from closer than ever before.