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Posted by: BruceMoomaw Apr 30 2006, 02:55 PM

(1) From the new EGU meeting ( http://www.cosis.net/abstracts/EGU06/10208/EGU06-J-10208.pdf ):

"Melt Structures in Comets" (Wallis and Wickramasinghe) --

"Since the three comets imaged at close quarters (cometsWild-2, Borrelly and Tempel-1) differ strongly in terrain types and overall topography, their history if not their origins were different.We see evidence of the three types of melting postulated for bodies containing substantial fractions of frozen H2O: a) early central melting due to radionuclides, impact melts resulting from hypervelocity meteorites or cometesimals, and
c) subcrustal melting due to solar heating of the dark (carbonaceous) outer surface. Though Tempel-1 currently has a similar orbit to the other two comets with q ~ 1.5 AU, its refrozen lakes imply that its dynamical history included a period of earthcrossing (q < 0.9 AU). Wild-2’s lumpy nucleus with broad flat-bottomed ‘craters’ would be the remnant interior shell and partially recrystallised region resulting from central melting." (This paper, however, was withdrawn for some reaon before the conference -- and, to my mind, the very fact that Wickramasinghe co-authored it calls it into some question, given his adherence to Fred Hoyle's screwball views on cometary bacteria.)

(2) From COSPAR ( http://www.cosis.net/abstracts/COSPAR2006/01776/COSPAR2006-A-01776.pdf : A conclusion that -- even if Comet Churyumov-Gerasimenko has the same extremely fluffy, loose dry powdery surface inferred by most of the Deep Impact team from the impact on Tempel-1 (<65 Pascals, or 0.68 grams per square cm) -- the Rosetta lander should sink at most 20 cm into the surface. "Slow penetration into cometary material depends primarily on the compressive strength, which is typically at least one order of magnitude higher than the tensile strength." (And, as Holsapple and Housen noted in LPSC abstract #1068, that conclusion regarding the softness of Tempel's suface is also open to doubt.)

(3) From the Spring AGU meeting ( http://www.agu.org/cgi-bin/SFgate/SFgate?&listenv=table&multiple=1&range=1&directget=1&application=sm06&database=%2Fdata%2Fepubs%2Fwais%2Findexes%2Fsm06%2Fsm06&maxhits=200&="P23A-04" ): John F. Cooper, who's always been interested in the effect of radiation on the surface chemical composition of icy bodies (such as Europa), concludes that this may account for the reddish tinge of many Kuiper Belt Objects and Centaurs, as well as the peculiar concentration of the most reddish KBOs in the ecliptic plane noted by some surveys (though not by all of them): "The red colors of low-inclination classical Kuiper Belt Objects at 40-50 AU, and Centaur objects originating from this same population, may arise from volume radiolysis of deep ice layers below more refractory radiation crusts eroded away by surface sputtering and micrometeoroid impacts."

Posted by: The Messenger May 1 2006, 02:19 AM

QUOTE (BruceMoomaw @ Apr 30 2006, 08:55 AM)

Posted by: ljk4-1 May 1 2006, 03:51 PM

Any missions planned for the rare A and D classes?

Polarimetric survey of asteroids with the Asiago telescope

Authors: S. Fornasier, I.N. Belskaya, Yu.G. Shkuratov, C. Pernechele, C. Barbieri, E. Giro, H. Navasardyan

Comments: 8 pages, paper accepted for pubblication on A&A

http://arxiv.org/abs/astro-ph/0604614