European spacecraft lands on comet 300M miles from Earth

20:50 European spacecraft lands on comet 300M miles from Earth 0 Comments

A few minutes past 11 a.m. ET, engineers received word that the spaceship, which belongs to the European Space Agency, had alighted safely on the comet's crater-scarred and boulder-filled landscape.

"We are sitting on the surface. Philae is talking to us," said a jubilant Stephan Ulamec, Philae lander manager. "We are on the comet."

"We can't be happier than we are now," said Andrea Accomazzo, Rosetta flight director.

The landing was successful despite a potentially disastrous failure. Dismayed engineers discovered before the landing that a thruster to help keep Philae on the comet's surface wasn't working. In the end, it didn't matter.

Philae and its carrier spacecraft Rosetta spent a decade just getting to the comet, launching from Earth in 2004 and finally pulling up in August next to comet Churyumov-Gerasimenko, also known as comet 67P. The comet, now more than 300 million miles from Earth, is tracing a 6 1/2-year oval around the solar system.

Rosetta's arrival at 67P gave scientists a thrill: The comet wasn't potato-shaped as had been expected but a complex rubber-duck shape. For mission engineers, the comet's profile was a nasty surprise rather than an intriguing revelation. That irregular shape made it trickier for Rosetta to orbit the comet and drop the lander in exactly the right place on the mountain-sized comet.

The comet's terrain also posed challenges. It is pocked with deep depressions and dotted with building-sized boulders, and it boasts slopes so steep that they make the toughest ski resort look tame. A lander that toppled onto its side would be worthless. So would a lander that bounced off the comet's surface.

Engineers aimed Philae at a relatively gentle landing zone, but they admitted before the spacecraft set off on its own that a safe arrival was not guaranteed.

"There is no doubt we will hit the comet," Accomazzo said before the landing. "Whether we hit it safely is another matter. … We have to be a bit lucky."

And they were. After Rosetta gave Philae a gentle shove, the lander drifted gently toward the comet, touching down on its three spindly legs at walking speed. The ship fired two harpoons into the comet to anchor itself. Ice screws on its three feet bit into the surface, described by Rosetta project scientist Matt Taylor as something between packed snow and cigarette ash. In the end, it didn't matter that a thruster that was supposed to help keep the spacecraft on the surface malfunctioned.

Now begins a frenzy of data gathering. The comet is drawing closer to the sun, which will eventually bring Philae's scientific career to an end, probably next March. The lander's 10 scientific instruments will snap pictures, sample chemicals, drill into the ground and more, hoping to learn more from this object made of scraps of the stuff that went into the formation of the planets. Eventually managers may command Rosetta too to make a soft landing on the comet's surface, reuniting the two spacecraft once more.