کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
1775866 | 1021209 | 2006 | 9 صفحه PDF | دانلود رایگان |
![عکس صفحه اول مقاله: Submillimeter Wave Astronomy Satellite observations of Comet 9P/Tempel 1 and Deep Impact Submillimeter Wave Astronomy Satellite observations of Comet 9P/Tempel 1 and Deep Impact](/preview/png/1775866.png)
On 4 July 2005 at 5:52 UT the Deep Impact mission successfully completed its goal to hit the nucleus of 9P/Tempel 1 with an impactor, forming a crater on the nucleus and ejecting material into the coma of the comet. NASA's Submillimeter Wave Astronomy Satellite (SWAS) observed the 110–101110–101 ortho-water ground-state rotational transition in Comet 9P/Tempel 1 before, during, and after the impact. No excess emission from the impact was detected by SWAS and we derive an upper limit of 1.8×107 kg1.8×107 kg on the water ice evaporated by the impact. However, the water production rate of the comet showed large natural variations of more than a factor of three during the weeks before and after the impact. Episodes of increased activity with QH2O∼1028 molecules−1 alternated with periods with low outgassing (QH2O≲5×1027 molecules−1). We estimate that 9P/Tempel 1 vaporized a total of N∼4.5×1034N∼4.5×1034 water molecules (∼1.3×109 kg∼1.3×109 kg) during June–September 2005. Our observations indicate that only a small fraction of the nucleus of Tempel 1 appears to be covered with active areas. Water vapor is expected to emanate predominantly from topographic features periodically facing the Sun as the comet rotates. We calculate that appreciable asymmetries of these features could lead to a spin-down or spin-up of the nucleus at observable rates.
Journal: Icarus - Volume 184, Issue 2, October 2006, Pages 602–610