[4] Impact site evolution: Image compilations

Attached are two montages of images showing the impact site on 20 of the 21 rotations since it was discovered, from July 19 to 27. There was no visible impact scar on the previous rotation (images from the USA by Rich Jakiel, Paul Rix, Fred Locklear, by courtesy of Anthony and the ALPO), so the impact occurred on the dark side some time between 07:40 and 14:00 on July 19.

In these montages, for each rotation, there is at least one of the best images, and a methane-band image if available, plus the professional images that have been released - but images that were in the hi-res set sent out earlier are not duplicated. Some images are included to show how the impact site remains undimmed right up to the limb, both in visible light and in the methane band, as was also observed for the SL9 impact scars.

There has only been modest development of the site in the week since the impact. On the first rotation it had a nearly-black oval core, 5000 km long, and an arc of ejecta ~9000 km in radius (smaller than some of the SL9 sites). The core has remained nearly-black, and become more elongated. The ejecta arc quickly became blurred, appearing as a small fan or patch following the core; so far it has not become more extensive. The scar of SL9 fragment Q1 was quite similar.

The infrared observations on July 20 at the NASA-IRTF by Dr. Glenn Orton and Dr. Leigh Fletcher not only confirmed the high-altitude cloud, they also detected a real 'smoking gun': "...evidence for high temperatures at the impact location, and suggestions of ammonia and aerosols that had been carried high into the atmosphere." [ http://blogs.jpl.nasa.gov/] Also on Mauna Kea on July 22, at the Gemini-North telescope, Dr. Imke de Pater and colleagues found: "The impact site is clearly much warmer than its surroundings." [ http://www.gemini.edu/node/11300 ] The heating and ammonia in the upper atmosphere could only have come from an explosion due to impact.

More fine images are coming in today, and the impact site is if anything more impressive than on its first rotation!


John Rogers, 2009 July 29.