Life on Mars?
Rolf
or
http://www.timesonline.co.uk/tol/news/science/space/article6934078.ece
Hope one of them works!
VoiceOfReason
Beware the sandworms. They're a bitch when they're hungry.
PG
hf1112$a4p$1...@news.albasani.net...
I'm still waiting for the promised NASA follow-up on this. The Times piece
is mostly hype, as usual. There isn't much from a recognised source on the
web as yet, although there is the following abstract on the Geochimica et
Cosmochimica Acta website - it was originally published in the November
issue of the journal of the Geochemical and Meteoritic Society. The full
article pdf has to be purchased, so only the abstract below:
"The Martian meteorite ALH84001 preserves evidence of interaction with
aqueous fluids while on Mars in the form of microscopic carbonate disks.
These carbonate disks are believed to have precipitated 3.9 Ga ago at
beginning of the Noachian epoch on Mars during which both the oldest extant
Martian surfaces were formed, and perhaps the earliest global oceans.
Intimately associated within and throughout these carbonate disks are
nanocrystal magnetites (Fe3O4) with unusual chemical and physical
properties, whose origins have become the source of considerable debate. One
group of hypotheses argues that these magnetites are the product of partial
thermal decomposition of the host carbonate. Alternatively, the origins of
magnetite and carbonate may be unrelated; that is, from the perspective of
the carbonate the magnetite is allochthonous. For example, the magnetites
might have already been present in the aqueous fluids from which the
carbonates were believed to have been deposited. We have sought to resolve
between these hypotheses through the detailed characterization of the
compositional and structural relationships of the carbonate disks and
associated magnetites with the orthopyroxene matrix in which they are
embedded. Extensive use of focused ion beam milling techniques has been
utilized for sample preparation. We then compared our observations with
those from experimental thermal decomposition studies of sideritic
carbonates under a range of plausible geological heating scenarios. We
conclude that the vast majority of the nanocrystal magnetites present in the
carbonate disks could not have formed by any of the currently proposed
thermal decomposition scenarios. Instead, we find there is considerable
evidence in support of an alternative allochthonous origin for the magnetite
unrelated to any shock or thermal processing of the carbonates."
So not quite as sensationalist as the Times Online piece, but interesting -
about as categorical as you'll find in a scientific paper with respect to
their conclusion that "the vast majority of the nanocrystal magnetites
present in the carbonate disks could not have formed by any of the currently
proposed thermal decomposition scenarios". The next step is for the
researchers to tell us what exactly they mean by an "alternative
allochthonous origin".
pg
Cory Albrecht
No problem if you have a working thumper and a pair of hooks.