Dust Outbursts From Comet 67P/Churyumov-Gerasimenko Observed by Rosetta-Alice

Abstract : The comet 67P/Churyumov-Gerasimenko, passed through perihelion on 13 August 2015. In the weeks surrounding the perihelion passage, several dramatic outbursts of dust have been observed by instruments aboard ESA’s Rosetta spacecraft. These outbursts are typically intense and short-lived, with timescales on the order of several tens of minutes to a few hours. We report on the two largest of these dusty outbursts observed by the Alice far-ultraviolet (700-2050Å) spectrograph, which occurred on 10 July 2015 and 22 August 2015. On 10 July 2015 02:06 UTC, Alice spectra of the sunward limb, nucleus and anti-sunward limb show typical levels of dust-scattered sunlight, with the sunward limb 3-4x brighter than the anti-sunward limb. Beginning around 02:10 UTC, the dust on the anti-sunward side of the nucleus brightened rapidly, increasing by a factor of 21 over pre-outburst levels, when integrated over a 10-minute exposure. A 40s exposure beginning at 02:20 showed an additional factor of two increase in brightness. During the outburst, the dust became significantly brighter than the sunlit nucleus. Concurrent NAVCAM images show a large dust cloud expanding out from the night side of the nucleus. Despite this forty-fold increase in dust brightness, the Alice data show no evidence of enhancements of H2O, CO, CO2, O2, O, or H in the post-outburst spectra. By 04:24 UTC, after a 2-hour data gap, the comet had returned to pre-event levels. Although complicated by the scanning motion of the spacecraft, the start of Alice observations on 22 August 2015 revealed a major dust outburst in progress, this time confined to the sunward side of the nucleus. Between 07:03 and 07:54, the brightness of dust on the sunward side faded by a factor of 7. NAVCAM images from this period also show a dramatic fan-shaped cloud of dust. Unlike the 10 July event, the 22 August event shows some evidence of increased gas emissions.
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Submitted on : Monday, November 16, 2015 - 6:56:52 PM
Last modification on : Friday, August 2, 2019 - 2:30:11 PM

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Andrew J. Steffl, Paul D. Feldman, Michael F. A'Hearn, Jean-Loup Bertaux, Lori M. Feaga, et al.. Dust Outbursts From Comet 67P/Churyumov-Gerasimenko Observed by Rosetta-Alice. 47th DPS Annual Meeting, Nov 2015, Washington, United States. pp.413.08. ⟨hal-01229544⟩

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