Search NASA⌕ Search

SEARCH · Search NASA

Results for “Monticello”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

3 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1987

Monticello - A glass-rich howardite

Monticello is a new howardite similar to Malvern in that it contains abundant (15 percent) glass fragments, which show a range of compositions from olivine-normative to quartz-normative. Like Kapoeta, it contains pyroxene grains that range up to highly magnesian compositions, Fs16. Because their pyroxenes are more magnesian than those occurring in diogenites, Monticello and Kapoeta are exceptions to the simple two-component mixing model in which howardites are considered to be mechanical mixtures of fragmented eucrites and diogenites. Monticello also contains clasts of what appear to be a cumulate eucrite and a noncumulate eucrite, as well as a radiating pyroxene chondrule from a chondrite. Monticello is a regolith breccia containing more evolved components than are usually considered in eucrite-diogenite genesis models. As such, it supports those models that involve reworking of a complex parent body crust rather than straightforward partial melting of primitive chondritic parent material.

Olsen, Edward J.↗
NASA NTRS1990

Chondrule-like objects and brown glasses in howardites

Chondrulelike objects and brown glasses were analyzed in the howardites, Bununu, Malvern, Monticello, Pavlovka, and Yamato 7308. The objects are very similar to chondrules in ordinary and carbonaceous chondrites. Like the brown glasses, the chondrulelike objects could have been produced by impact melting that left some crystalline nuclei, followed by a slower cooling rate than for the glasses. Alternatively, these objects are chondrules implanted from chondrite impactors. They are, however, without rims or any adhering matrix. The brown glasses appear to represent melting of average regolithic surface material, except for Monticello and Y7308, both of which have some siliceous glasses. The siliceous glasses could not have been produced by vapor fractionation but by melting of differentiated lithologies such as fayalitic granites. Impact mechanics indicates that howardites with abundant brown glasses came from an asteroid larger than Vesta (greater than 400 km radius), upon which impacts occurred at relative velocities of up to 5 km/s. Howardites with little or no brown glasses came from a smaller parent body. It is concluded that at least two parent bodies are likely sources for the basaltic achondrites.

Olsen, Edward J.↗