Rosetta Finds Out About Comet 67P/Churyumov-Gerasimenko

A November image of Comet 67P/Churyumov-Gerasimenko shows faint jets of gas and dust. (PHOTO CREDIT: European Space Agency)
A November image of Comet 67P/Churyumov-Gerasimenko shows faint jets of gas and dust. (PHOTO CREDIT: European Space Agency)

Photographs and data from the European Space Agency’s Rosetta spacecraft have provided an unprecedented close-up examination of a comet, but there is one thing that has not shown up yet: the small lander that bounded to the surface in November.

Scientists working on the mission described their initial observations of Comet 67P/Churyumov-Gerasimenko in seven articles published Thursday in the journal Science. “This sets the baseline for the rest of the mission,” said Matt Taylor, the project scientist.

Rosetta arrived at the comet in August after a trip of 10 years and four billion miles. For the first time, scientists are having an extended look at a comet as the spacecraft accompanies it for at least a year as it swings around the sun. As the comet heats up, it will spew greater amounts of gas and dust.

In November, a washing-machine-size lander named Philae made it to the surface, but systems designed to anchor it failed, and the lander bounced, ending far from the intended site in a position that greatly reduced the amount of sunlight hitting its solar panels. Instruments on the lander operated for two days until the batteries drained.

In mid-December, the orbiter’s high-resolution camera took pictures of the spot where the scientists think the lander ended up, but the scientists were not able to find it — a few pixels in a four-million-pixel image.

Holger Sierks, the principal investigator for Rosetta’s main camera, said that Philae, which photographed its surroundings and performed various measurements after landing, was still expected to awake in the spring when increasing sunlight recharged the batteries. Even if Philae does not wake up, Rosetta should be able to spot it after the comet has made its closest approach to the sun, in August.

The high-resolution camera has taken photographs with a resolution as fine as two and a half feet per pixel. The comet, just two and a half miles wide with a two-lobe shape that resembles a rubber duck toy, has a remarkably wide variety of terrain. That includes smooth dust-covered regions, fields of boulders, steep cliffs and large depressions that may have been blown out by underground melting of carbon dioxide. The variety is surprising because many think the comet is, by and large, made of the same material throughout. Scientists are not sure if the shape comes from two smaller comets that bumped and stuck together or one large comet that eroded in an unusual manner.

On the surface of Comet 67P, there are even what look like ripples of sand dunes like those seen on Earth and Mars. That appears befuddling, as a comet has no atmosphere — and so no wind — and only a wisp of gravity.

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SOURCE: NY Times | Kenneth Chang

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