Sterling K. Webb wrote:
Maybe it hit Planet V-for-Five. Maybe it WAS
Planet V-for-Five or a good chunk of it. Or a satellite of Planet
V-for-Five dragged along for the ride when its
orbit became unstable. Or... I look at my little chunks of mesosiderite
with new respect. I sidle up to them at the bar and buy them a drink in
the hope that they will tell me their life story...
Sterling,
It may be just another one of those O-isotope coincidences, like the
fact that E chondrites have O-isotopic values that are indistinguishable
from those of the Earth, or that brachinites have values that are
identical to the HEDs, but a new O-isotope study by Greenwood et al.
(http://www.lpi.usra.edu/meetings/lpsc2006/pdf/1768.pdf) of numerous
mesosiderites demonstrates that their oxygen isotopic values are almost
identical to those of the HED clan, which suggests that there may be a
genetic link between them. The results suggest that both HEDs and
mesosiderites may be derived from Vesta; or, if you want to speculate
like me - I think the arrival of Dawn (in Sept. 2011) will reveal that
HED and MES meteorites were derived from a separate, significantly
disrupted, Vesta-like PB. This latter possibility may leave the door
open for a possible Planet V origin for these two groups.
David
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