New Rosetta pix show comet craters – only 6 days to go!

The nucleus of comet 67P/Churyumov-Gerasimernko as seen from a distance of 1,200 miles (1,950 km) on July 29th, 2014. One pixel corresponds to approximately 121 feet (37 m). The bright neck region between the comet’s head and body is becoming more and more distinct. Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

Closer, closer, closer. Rosetta sent back more detailed images taken on July 30 that confirm the comet’s bright neck collar and show much more surface texture than earlier photos – including two craters! The collar’s light tone hints of fresh ice vaporizing in sunlight but could also be caused by different materials on that part of the comet’s surface. Maybe the next round of photos will offer a clue.

Two distinct craters stand out in this lower resolution navigation camera photo. What started out looking like a rubber ducky now reminds me of a primitive bird. The bright collar is also seen from this point of view. In 6 days, Rosetta will enter orbit around the comet. Credit: ESA/Rosetta/Navcam

The wider-view navigational camera sent back an even more fascinating image showing dual craters, one on each lobe, with hints of other crater or depressions in the ice. Comets, including 67P C-G, are made of mostly water ice and dry ice or frozen carbon dioxide. The ices act as glue to hold the dust, sand-sized grains and pebbly pieces of the comet together.

The inner coma of comet 67P/Churyumov-Gerasimenko is about 93 miles (150 km) across.  This image was taken on July 25th, 2014. The hazy circular structure on the right and the center of the coma are artifacts due to overexposure of the nucleus. Credit: ESA

When a comet’s orbit takes it into the inner solar system, some of the ice vaporizes, releasing dust and grit, along with a variety of gases like carbon monoxide, methanol, ethane and ammonia. The melange forms the comet’s coma or temporary atmosphere.

Next, the pressure of sunlight pushes back coma gases and dust to form tails – one of dust and the other of gas.

As Rosetta’s camera tried to record the coma, which is much fainter than the nucleus, the brighter nucleus was overexposed, creating an artifact. Taking pictures of comets is challenging enough, but evidently even more so when you’re standing right next to one!

* UPDATE 8/1: The ‘craters’ are more likely artifacts in processing of the image according to other sources.

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About astrobob

My name is Bob King and I work at the Duluth News Tribune in Duluth, Minn. as a photographer and photo editor. I'm also an amateur astronomer and have been keen on the sky since age 11. My modest credentials include membership in the American Association of Variable Star Observers (AAVSO) where I'm a regular contributor, International Meteorite Collectors Assn. and Arrowhead Astronomical Society. I also teach community education astronomy classes at our local planetarium.

One thought on “New Rosetta pix show comet craters – only 6 days to go!

  1. The photos are nice. Philae module will reveal that the comet 67P nucleus is the D-type asteroid (from Trojans or Hilda populations).

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