Rosetta may have spotted comet’s primordial ingredients

SAN FRANCISCO — The dynamic, rugged terrain of comet 67P/Churyumov-Gerasimenko may be exposing the meter-wide building blocks that make up the comet, scientists reported December 17 at the American Geophysical Union’s fall meeting. If confirmed, the finding could give scientists an unprecedented look at pristine samples of the original material that bonded to form comets, asteroids and planets nearly 4.6 billion years ago.

The enticing evidence was delivered by the Rosetta spacecraft’s OSIRIS instrument, which snaps photos of the comet’s surface with a resolution as high as a few centimeters per pixel. The images quickly revealed that 67P violates the conventional wisdom of comets resembling smooth dirty snowballs, said Holger Sierks, a member of the Rosetta team. The photos, which are not yet available to the public, reveal cliffs tens or hundreds of meters tall, as well as mysterious pits, so

me about as long as two football fields and just as deep, that are venting gas into space.

But it was the components of the cliffs and pits that caught Sierks’ eye. Embedded along the edges of those features are strange spheres, most between 1 and 3 meters in diameter. He hypothesizes that the spheres are examples of the fundamental units of ice and dust that were sintered together in the infant solar system to form asteroids, planets and comets like 67P.

Editor’s note: This article was updated on January 22, 2015, to include the images in question of comet 67P’s surface.