Fluidization and multiphase transport of particulate cometary material as an explanation of the smooth terrains and repetitive outbursts on 9P/Tempel 1

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.icarus.2008.11.012 Byline: Michael J.S. Belton (a), Jay Melosh (b) Keywords: Comets; nucleus; Geological processes Abstract: The Deep Impact mission discovered repetitive outbursts on Comet 9P/Tempel 1 and the presence of several smooth terrains on its surface. We present new measurements of the extent of the smooth terrains, the slopes along their centerlines, and the areas of their likely source regions. Our analysis of these features indicates that they are 0.3 m in size should become fully relaxed during the emplacement time explaining the smooth texture seen in the images. In contrast, the repetitive outbursts require a gas-laden reservoir to have formed in the vicinity of the phase change boundary well below their preferred location. We visualize the outbursts to be the result of either spouting or bubble transport to the surface where the release of gas is diurnally modulated by either thermal stresses or H.sub.2O sublimation back pressure. The source region for the i2 smooth terrain is found to coincide with an H.sub.2O-ice rich area and we propose that the process of elutriation, i.e., the separation of different classes of particulates depending on their drag properties, occurs in the fluidized material as it flows up to and through the surface. In this way the material becomes enhanced in H.sub.2O crystals relative to siliceous and carbonaceous particulates. Author Affiliation: (a) Belton Space Exploration Initiatives, LLC, 430 S. Randolph Way, Tucson, AZ 85716, USA (b) Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721-0092, USA Article History: Received 6 August 2008; Revised 15 November 2008; Accepted 20 November 2008