Spacecraft lands on speeding comet
Print Edition
THE European Space Agency landed a probe on a comet yesterday, a first in space exploration and the climax of a decade-long mission to get samples from what are the remnants of the birth of Earth’s solar system.
The box-shaped 100-kilogram lander, named Philae, touched down on schedule at about 1600 GMT after a seven-hour descent from spacecraft Rosetta around half a billion kilometers from Earth.
Scientists hope that samples from the surface of 67P/Churyumov-Gerasimenko will help show how planets and life are created as the rock and ice that make up the comet preserve organic molecules like a time-capsule.
Comets come from the formation of Earth’s 4.6-billion-year-old solar system. Scientists believe they may have brought much of the water in Earth’s oceans.
“We are ready to make science fiction a science fact,” ESA director of human spaceflight and operations, Thomas Reiter, said at the European Space Operations Centre in Germany before the landing.
Rosetta reached the comet, a roughly 3-by-5 kilometer rock discovered in 1969, in August after a journey of 6.4 billion kilometers that took 10 years, five months and four days — a mission that cost close to 1.4 billion euros (US$1.8 billion).
Rosetta is the first spacecraft to orbit a comet rather than just flying past to take pictures.
Yesterday’s launch went ahead despite a problem with the thruster that meant the probe had to rely mainly on its harpoons to stop it bouncing back from the comet’s surface.
The three-legged lander had to be released at exactly the right time and speed because it cannot be controlled on its descent. On its way down, Philae gathered data and images, which were relayed back to Earth.
Engineers designed the lander not knowing what type of terrain they would find on the comet’s surface. Rosetta has been taking pictures of the comet and collecting samples from its atmosphere as it approaches the sun, showing it is not as smooth as initially hoped, making landing more tricky.
The surface is also more dusty than expected, limiting light needed to charge its solar panels and power its instruments once its batteries run out after two and a half days.
Scientists have likened the trillion or so comets in our solar system to time capsules that are virtually unchanged since the earliest moments of the universe.
“By studying one in enormous detail, we can hope to unlock the puzzle of all of the others,” said Mark McCaughrean, a senior scientific adviser to the mission.
ESA had announced hours before the release that a third component — an active descent system that uses thrust to prevent the lander from bouncing off the surface of the low-gravity comet — could not be activated.
During the descent, scientists were powerless to do anything but watch, because the vast distance to Earth made it impossible to send instructions in real time. It takes more than 28 minutes for a command to reach Rosetta.
Rosetta, which was launched in 2004, had to slingshot three times around Earth and once around Mars before it could work up enough speed to chase down the comet, which it reached in August. Rosetta and the comet have been traveling in tandem ever since.
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