Ten new Rosetta images that reveal comet 67P in all its glory

In August 2014, the European Space Agency’s Rosetta spacecraft arrived at comet 67P/Churyumov-Gerasimenko. Once in orbit, it swooped as low as 10 kilometers to get unprecedented data from the comet (and to drop off its short-lived Philae lander). Today, Science is publishing a suite of new papers detailing some of the mission’s first findings, including discoveries from Rosetta’s main science camera, OSIRIS (Optical, Spectroscopic, and Infrared Remote Imaging System). Images like these reveal 67P to be a far more diverse place than anyone expected.

1. Crazy quilt, with a history

OSIRIS

Mission scientists have assigned ancient Egyptian names to the different surface regions of the duck-shaped comet. Two regions on the “wings” of the duck—Aten and Anubis—are smooth and contain depressions that may mark sites where the comet shed large chunks of material in the geologically recent past.

2. Active pits

ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

The comet spews material into space from the pits that dot the surface. Some are inactive and are partly filled with dust. Others appear to be turning on again: As 67P approaches the sun, subsurface ice deposits heat up and create jets of gas and dust.

3. Erosion from cliff faces

OSIRIS

The comet also erodes from cliff faces. As ice sublimes, chunks of material drop to 67P’s surface, exposing the next layer of the cliff face to erosion. (In pits, dust can fall back and stanch jetting activity by blocking the sun.)

4. Which way is down?

ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

Because of the comet’s lopsided shape and weak gravity, boulders and dust appear to move in strange ways. In this image, red regions show unstable slopes that sit at more than 45° angles to the local gravity field.

5. Where the action is

ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

Still far from the sun, 67P’s activity levels have been subdued. So far, most of the jetting has been seen around the neck.

6. Why the neck?

ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

Nobody knows. Oddly, calculations show that the neck region receives the least sunlight (top) of any part of the comet. Even when reflections and reradiation of this heat is accounted for (bottom), the neck is still colder than the rest of the comet.

7. Crick in the neck

ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

In any case, 67P might not keep its ducklike shape for long. Cracks around the neck suggest that the comet’s “head” and “body” flex there. Someday the two lobes could rupture and go their separate ways.

8. Goosebumps

ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

One of the most surprising features discovered by OSIRIS is nodules, a few meters across, that the team is calling “dinosaur eggs” or “goosebumps.” Seen in pits and cliff faces, the nodules could represent the fundamental building blocks of the comet.

9. Comet vomit

OSIRIS

OSIRIS has also discovered a pit that seems to have belched out a fluid material—a sign that gas pressures can build up in the subsurface and create complex, fluid mixtures of gas and dust.

10. Windlike features (ripples and tails behind boulders)

OSIRIS

The gases don’t only shoot up; they may also work sideways, creating ripples and other windlike features that look out of place on a body without an atmosphere.

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