Comet-chasing Rosetta spacecraft sends lander down


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This scene features the boulder named Cheops, the largest and brightest boulder towards the top left of the image. It measures about 45 m across and 25 m high. Cheops and the surrounding cluster of boulders reminded scientists of the famous pyramids at Giza near Cairo in Egypt, and so it was named for the largest of those pyramids, the Great Pyramid, which was built as a tomb for the pharaoh Cheops around 2550 BC. Another large boulder lies towards the bottom of this frame and is surrounded by many smaller boulders that seem to be appearing from beneath the smooth, dusty material that dominates this scene. The smooth region extends to the top right of this frame, where rougher terrain appears to be exposed beneath it. 

Europe’s Rosetta spacecraft today sent a probe down to land on a comet between the orbits of Mars and Jupiter, the culmination of a decade-long mission.
Rosetta’s landing craft, Philae, separated from its mothership about 9:35 a.m. Paris time, embarking on a seven-hour descent to the comet, according to a webcast on the European Space Agency’s website. The success of the maneuver was known 28 minutes later, and mission staff cheered and hugged each other at ESA’s operations center in Dartmstadt, Germany.
“Now Philae has gone and is on its path down to the comet,” Spacecraft Operations Manager Andrea Accomazzo said on the webcast. “It worked flawlessly in the last minutes.”
Scientists hope to glean information about the early evolution of the solar system by studying the comet named Churyumov-Gerasimenko. Comets date back 4.6 billion years to when the planets were forming, and the icy bodies may have seeded Earth with the organic molecules that became the building blocks for life.

In this scene from the large lobe of Comet 67P/Churyumov–Gerasimenko, sets of long, parallel grooves and ridges in the foreground draw the eye up to a block of layered material (appearing as vertically stacked layers in this orientation) in the centre of the frame. This ridge traces up to a peak in the distance, through a cascade of boulders. To the left, flat-topped steps contrast against a ‘pinnacle’ seen against the horizon. To the right, a patch of brighter material lies crumbled at the base of a steep wall – perhaps signalling material that has been freshly exposed.
“This is the first mission that puts a lander down on a comet, so there are a lot of new opportunities to do science,” said Gerhard Schwehm, a consultant and manager of the mission from its liftoff until he retired from the space agency last year. “We will not find life, and we won’t be able to answer the question tomorrow how did life emerge on Earth. But if we see organic molecules, we can say ‘Oh, the comets could have brought very complex molecules to the early Earth.’”
August orbit
Rosetta, launched in March 2004, has been orbiting the comet since Aug. 6, gleaning information about the mass of dirty ice, dust and gas, and scoping out a suitable site to place Philae. Researchers selected a site based on the perceived ease of landing, the exposure to sunlight to fuel Philae’s solar cells, and hints of interesting nearby activity that the lander could observe.
Rosetta’s 11 instruments have been monitoring the comet and gas and particles thrown off it. It’s scheduled to orbit the comet until the end of 2015. Philae, which has 10 instruments, will take pictures of the comet, as well as drill 23 centimeters below the surface to retrieve samples that can be taken up into the craft and heated. The molecules that are released will then be analyzed, said Schwehm.
‘The Cherry’
“If you want to see what the comet is really made of, you have to go there, you have to land and study it,” he said. “It’s the cherry on the cake that gives the Rosetta mission extra taste.”
The 6.5 billion-kilometer journey has taken Rosetta as far as 1 billion kilometers from Earth. It’s now orbiting about 22.5 kilometers above the comet, more than 500 million kilometers from Earth and about 450 million kilometers from the Sun, between the orbits of Mars and Jupiter, according to the ESA website.
Astrium, now part of Airbus Defence and Space, was the main contractor for the spacecraft launched on March 2, 2004. The European Space Agency was formed in 1973 and has 20 member countries, including the U.K., Germany and France.

This view focuses on the boulder-strewn neck region of Comet 67P/Churyumov–Gerasimenko, with the smaller lobe on the left and the larger lobe on the right. Much of the comet’s activity originates from the neck. The scene also shows the contrast between the rugged material in the cliff walls rising up to the smaller lobe and the soft, more ‘textured’ material that characterises the neck and that is also coating the larger lobe in this region.

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