Howardites, eucrites, and diogenites

Oxygen isotope variations in differentiated bodies—such as Earth, Moon, Mars—and the parent body of the HED group (for howardites, eucrites, and diogenites) show characteristic mass-dependent fractionation lines, with a slope of 0.52 on the three-isotope plot... 

Ruzicka A., Snyder G. A., and Taylor L. A. (1997) Vesta as the howardite, eucrite and diogenite parent body impfications for the size of a core and for large-scale differentiation. Meteorit. Planet. Sci. 32, 825—840. 

Welten K. C., Lindner L., van der Borg K., Loeken T., Scherer P., and Schultz L. (1997) Cosmic-ray exposure ages of diogenites and the recent collisional history of the howardite, eucrite, and diogenite parent body/bodies. Meteorit. Planet. Sci. 32, 891-902. 

HED The meteorite association comprising howardite, eucrite, and diogenite types of meteorites thought to be derived from the asteroid 4-Vesta. 

Mittlefehldt D. W. (1979) Petrographic and chemical characterization of igneous lithic clasts from mesosiderites and howardites and comparison with eucrites and diogenites. Geochim. Cosmochim. Acta 3, 1917-1935. 

In most respects, asteroid 4 Vesta is geochemically similar to the Moon. As judged from howardite-eucrite-diogenite (HED) meteorites (see Chapter 6), Vesta is an ancient, basalt-covered world (Keil, 2002). Its rocks are highly reduced, and its depletions in volatile and siderophile element abundances resemble those of lunar basalts. And like the Moon, Vesta is hypothesized to have had an early magma ocean. The exploration of Vesta is now in progress, and within a few years we may have enough data to discuss it in a similar way that we have considered the Moon. 

Goodrich C. A. and Righter K. (2000) Petrology of unique achondrite Queen Alexandra Range 93148 a piece of the pallasite (howardite-eucrite-diogenite ) parent body Meteorit. Planet. Sci. 35, 521—535. 

Pun A., Keil K., Taylor G. J., and Wider R. (1998) The Kapoeta howardite implications for the regolith evolution of the howardite-eucrite-diogenite parent body. Meteorit. Planet. Sci. 33, 835-851. 

Just two major impact events, one at —20 Myr and the other at —40 Myr, on one body could account for the great majority of the eucrites, howardites, and diogenites reaching Earth today. One or more events at earlier times also seem likely. 

Figure 9. Exposure age distributions of HED meteorites (howardites, eucrites, diogenites) and aubrites or enstatite achondrites. The HED data are from the compilation by Welten et al. (1997), with only the (shielding corrected) Kr-Kr ages being displayed for the eucrites. Included are 4 new diogenite ages from Welten et al. (2001b). In addition, the -3 Myr age of the howardite Kapoeta has been added (Caffee and Nishiizumi 2001). For data sources of aubrites see text. Note the different abscissa scales between the lowermost panel and the others.

Fig. 18.25 Lunar basalt (open circles) collected by the Apollo astronauts and lunar meteorites (solid circles) collected in Antarctica occupy a well-defined area in coordinates of their Fe/ Mn, K/La, and (Fe/Sc) x 0.01 ratios. The achondrites of the HED (Howardite, Eucrite, Diogenite) groups (crosses) lie in a separate field. The SNC (solid triangles) meteorites (Shergottites, Nakhlites, Chassignites) originated from Mars. The sample numbered 1 is ALHA 81005 and 2 is Calkalong which was recovered in the Australian desert. The Fe/Sc ratio was reduced by a factor or 0.01 in order to prevent the data points from crowding into the Fe/Sc corner of the triangle (Data for ALHA 81005 from Korotev et al. 1983 and for the other samples from Hill et al. 1991)...

Eugster O. and Michel T. (1995) Common asteroid break-up events of eucrites, diogenites and howardites, and cosmic-ray production rates for noble gases in achondrites. Geochim. Cosmochim. Acta 59, 177-199. 

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