Collisional History of Gaspra

Submillimeter Wave Astronomy Satellite observations of Comet 9P/Tempel 1 and Deep Impact

“…The non-detection of water vapor due to the Deep Impact event argues against the impact of meteoritic material as the origin of the natural outbursts observed in 9P/Tempel 1. This is suggested by the small amount of water released by the impact when compared to the natural outbursts, and by the fact that this would require an abundance of meteorites in interplanetary space far higher than all other observations permit in order to explain the number of outbursts observed in 9P/Tempel 1 (eg., Lang, 1992;Ceplecha, 1992;Greenberg et al, 1994, and references therein). Another argument against exogenic processes, by Earth-based instruments are summarized by Meech et al (2005a), but it is not always possible to exactly constrain the timing of these outbursts because of the limited time coverage of these observations and because tracers other than water were observed in most cases.…”

The Monahans chondrite and halite: Argon‐39/argon‐40 age, solar gases, cosmic‐ray exposure ages, and parent body regolith neutron flux and thickness

“…Regoliths are developed from impacts into underlying bedrock, and a deep mature regolith is expected to exhibit characteristics of long irradiation times and extensive mixing, as is the case for regoliths developed on lunar mare. Some early theoretical models of asteroid regoliths predicted thin regoliths (Chapman, 1976), but recent flybys of a few asteroids suggest the likely presence of substantial regoliths (Greenberg et al, 1994). We envision that a regolith developed on a fresh rock surface for -18 Ma on the early H-chondrite parent asteroid, then was deeply covered by ejecta from a very large impact and protected from cosmic rays and major impacts until Monahans was ejected into space as a meteorite -6 Ma ago.…”

Tidal Distortion and Disruption of Earth-Crossing Asteroids

“…Phobos lend credence to this theory: Ida, with dimensions Without question, the most famous disrupted comet is of 60 ϫ 26 ϫ 18 km, has one ȁ23-km crater and five D/Shoemaker-Levy 9 (SL9), which broke into more than ȁ10-km craters (Belton et al 1994b, Thomas et al 1996; 20 similar-sized fragments during its penultimate encounGaspra, with dimensions of 18 ϫ 11 ϫ 9 km, could have ter with Jupiter in 1992, when it passed within 1.6 jovian as many as eight craters larger than 4 km in diameter radii of the planet center (Sekanina et al 1994). Asphaug (Belton et al 1994a, Greenberg et al 1994; Phobos (dimen-and Benz (1996) found that SL9's disruption into a ''string sions 27 ϫ 22 ϫ 19 km) is dominated by the large 11-km of pearls'' could have occurred only if the comet were crater Stickney (Asphaug and Melosh 1993). Numerical virtually strengthless (cf.…”

“…Another tidally dishydrocode simulations of these crater-forming events indi-rupted comet (of less renown) is P/Brooks 2, which broke cate the target, in each case, is left with a highly damaged into at least 8 fragments when it approached within 2 jovian and fragmented structure (Asphaug and Melosh 1993, radii of Jupiter in 1886 (Sekanina and Yeomans 1985). Greenberg et al 1994Greenberg et al , 1996.…”

“…The size and orbital distribution of the ejecta are discussed, a crater is controlled by the target's gravity rather than by along with the applications of this technique towards an underphysical strength (Greenberg et al 1994, 1996, Love and Ahrens 1996. Craters formed in the gravity regime require a weak or fragmented target much ''strength'' regime; instead such an impact would have its gravitational acceleration, at which point it begins to shed mass along its equator, disrupted the target if it were a monolithic body of unshattered rock.…”