Geology Reference
In-Depth Information
and pairing group
Howardite
1734.5 g
Found December 21, 1987
16.5 cm × 10 cm × 8.5 cm,
Weathering = A
because fragments of both are preserved in the brecciated achondritic
meteorites known as howardites. Howardites contain a minimum of >10%
of either eucritic or diogenitic material in order to be classified as such.
They are also polymict breccias, and sometimes contain glassy spherules
that presumably formed in the regolith process. Some howardites contain
clasts of carbonaceous chondrite material, indicating a mixture of lithol-
ogies in some asteroid regolith.
12
Cl
8
4
CM
CR
0
-4
C3
CAI
-8
-4
0
4
8
12
16
20
24
δ
18
0 (‰ rel. SMOW)
Plate 61
MiNERALogy
SigNiFiCANCE
EET 87503 displays a variety of fine- to coarse-grained
diogenite, eucrite (multiple varieties), impact melt/brec-
cia, glassy, and even carbonaceous chondrite clasts in a
light gray matrix.
EET 87503 contains a great diversity of materials that are
likely from the regolith of asteroid 4 Vesta. Among the
materials found are clasts of carbonaceous chondrites
(right, [449]). in some other howardites the portion of
carbonaceous chondrite material can be very high, as
much as 50% of some sections. Careful studies of the
clasts in howardites can lead to a detailed understanding
of the processes acting on the surface (or regolith) of an
asteroid, and also offer insight into magmatic history.
References [444-454]
