[meteorite-list] Mercurian Meteorites - A Repost

From: Bernd Pauli HD <bernd.pauli_at_meteoritecentral.com>
Date: Thu Apr 22 10:06:18 2004
Message-ID: <3DE677FC.7C33182B_at_lehrer.uni-karlsruhe.de>

aziz habibi wrote:

> what i hope is that this stone turn to be from mercury.
> so my question for the list as i want here to open a debat,
> o-isotope anlysis can they say for sur if a stone is from
> mercury or not??

Hello All,
and best regards,

Bernd


LOVE S.G. et al. (1995) Recognizing mercurian
meteorites (MAPS 30-3, 1995, 269-278):

Summary and Conclusions

The existence of meteorites from Mars and the Moon implies that impact
launch of rocks from Mercury is likely. Orbital evolution of such
materials to Earth-crossing orbits appears possible, but its efficiency
is probably < 1% of that computed for Mars (Wetherill, 1984). Scaling to
the number of known martian meteorites, we estimate at best a ~ 10%
chance that a mercurian rock could exist in current meteorite
collections. These odds are low, but they are not zero. As meteorite
collections grow in the future, the probability can only improve. We
should recall the lesson of the unforeseen lunar and martian meteorites
and be prepared to accept Mercury as a potential meteorite parent body.
As with meteorites from other planetary bodies, identifying a mercurian
meteorite would be problematic (e.g., Lindstrom et al., 1994). Our
ignorance of the properties of Mercury complicates the process of
identifying a mercurian meteorite but at the same time increases its
potential scientific value. We believe that mercurian meteorites
originate in the stony outer layers of a differentiated planet. They may
possess an unusual isotopic composition. Rocks from Mercury are probably
low in volatiles and are derived from a planet with a bulk composition
moderately enriched in refractory oxides of Al, Ti, and Ca. Their FeO
contents are not more than ~ 5%, and possibly much lower. The ages (~3.7
to ~ 4.4 Ga) of primary mercurian rocks may overlap with those from the
Moon, Mars, and the asteroids. Mercurian regolith breccias (the easiest
type of rock to recognize as having originated on Mercury) should be
rich in micrometeorite craters, exogenic chondritic materials,
agglutinates, and impact vapor deposits. They should show a lower
solar-wind content than lunar soils of similar maturity, and the
implanted gas may be fractionated by interaction with Mercury's global
magnetic field. Mercurian surface rocks should contain a uniquely high
solar-to-galactic cosmic-ray damage track ratio.
Although some information on Mercury's magnetic history, thermal
environment, and radar properties is available, it is of questionable
utility in identifying mercurian rocks. Launch-induced shock damage in
mercurian meteorites may be comparable to or greater than that seen in
martian ones, but this constraint is very weak.
Applying the above criteria to the currently recognized meteorite
groups, we find that none match the predicted properties of mercurian
rocks. The groups in which a misclassified mercurian meteorite would be
most likely to lurk are differentiated, low-FeO objects such as the
lunar anorthosites and the aubrites. Future searches for mercurian
meteorites should focus on similar objects.
Recognizing mercurian meteorites would be greatly simplified if we had
better knowledge of the elemental and mineralogic composition of the
planet, which could be obtained with a relatively simple and inexpensive
spacecraft mission. Judging from the case of the lunar meteorites,
however, confident identification of a mercurian meteorite will probably
not become possible until we have obtained detailed analyses - either in
situ or in the laboratory - of known samples of the planet.
Received on Thu 28 Nov 2002 03:09:32 PM PST