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February 11, 2012
4:52 AM
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 Summary of Preliminary Mission Results
Information about the pre-impact nucleus, or solid body, of the comet
The nucleus was very different from all comets visited previously, both in large-scale shape and in small-scale topography.
The ratio of its length to its width is smaller than predicted from Earth-based data but the average diameter is in good agreement with previous conclusions, i.e. about 6 km average diameter.
The surface of Comet Tempel 1 was as black as charcoal or blacker.
Surface features as small as a few meters were seen.
There are numerous circular features on the surface of the comet, some of which may be classical impact craters.
The axis of rotation is still somewhat uncertain but appears to point in the same general direction as Earth's rotational axis. This is consistent with one of the two positions predicted as likely prior to the encounter.
There are jets in the coma, but the coma is faint compared to the nucleus.
The comet undergoes spontaneous outbursts, some of which were seen from Earth.
H2O, CO2, CO, and hydrocarbons were seen in the spectra of the outburst material *Unidentified spectral features (previously unseen in comets) in the near infrared were observed by the spacecraft during at least one of the outbursts.
The cratering event
The impactor spacecraft hit the surface of the comet at an angle, probably 20 to 45 degrees above horizontal
Most of the solid particles ejected were tiny (microscopic). The impact could not pulverize a large volume to these small particles so the preexisting material must have been very fine.
Because most of the ejected particles were very small, the cone of ejected material was very bright and opaque.
The formation of the crater was controlled primarily by the comet's very weak gravity, and therefore the material of the comet is very weak, weaker than snow.
Mission scientists infer that the crater created by the impact was larger than 100m in diameter, but they have not yet been able to tease out an image from behind the cloud of ejecta. "The crater was at the large end of our range of expectations," said Michael A'Hearn.
There was an early ejection of hot vapor that led to the crescent of material seen expanding rapidly away from the comet. As the hot vapor moved across the spectrometer slit on board the flyby spacecraft, the H2O and the CO2 were hot, between 1000K and 2000K, and the emission by hydrocarbons was strongly enhanced.
Only a few seconds of data from the spectrometer have been analyzed. There are unidentified spectral features.
Future Operational and Program Issues
NASA authorized the Deep Impact mission to carry out a maneuver to place the spacecraft on a trajectory that would enable an extended mission to comet Boethin. This maneuver was carried out in late July. NASA also authorized a small amount of additional funding to monitor the health and safety of the spacecraft. The funding is given quarter by quarter and is at an absolutely minimal level. NASA has not made a decision on an extended mission.
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 Information provided by the Office of University Communications
Email University Communications at emailum@umd.edu
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