|
Several observations make this finding exciting news and are
an enrichment of meteoritical sciences. This meteorite is the
first Martian meteorite found in the hot desert climate of
the Sahara. It is the first one found since 1994 and also the
first since the discussion wether there is life on Mars began
two years ago. Now, the number of Martian meteorites has
increased to a total of 13, a small number if compared to the
total of more than 20,000 meteorite specimens known so far. A
fragment of the meteorite was given to the Max Planck
Institute for Chemistry in Mainz by a private finder for
scientific purposes. The rock weighs a little over 2 kg and
is shaped like a loaf of bread.
During a five-minute speech, Zipfel presented results from
inert gas, chemical and mineralogical studies. The inert gas
inventory of the atmosphere of Mars is very characteristic
and well known from the Viking mission measurements on the
surface of Mars in 1976. This is, so far, the strongest
evidence that meteorites having this inert gas fingerprint
must come from Mars. Inert gases present in this meteorite
clearly puts it in the group of Martian meteorites. Typical
elemental ratios obtained by bulk chemical analyses of a chip
of the new meteorite soon confirmed this finding. In
addition, mineral chemistry and petrographic observations,
such as the presence of feldspathic glass, rounded out the
picture. We had no doubt that this was a Martian
meteorite, said Zipfel, who made the announcement at
the MSM in Dublin.
During the meeting, Zipfel gave British scientists from the
Open University a 150 mg sample for analysis of the oxygen
isotopic composition of the meteorite. These measurements
were carried out one week after the Dublin announcement and
their results are consistent with findings obtained by the
Max Planck scientists.
Inert gas analyses show that this meteorite was ejected from
Mars about 1 million years ago, marking an ejection event
unknown from other Martian meteorites, said Zipfel in her
presentation. After that, the meteorite took its time to
travel through space before it was captured by the gravity of
the Earth and landed in Northern Africa. It was collected
there in May of this year and immediately brought to the
German Max Planck Institute for classification. The meteorite
is the first find of its group in a hot desert environment.
Clearly, it carries along with it its desert history, in that
it is penetrated throughout by veins filled with terrestrial
weathering products. The search for past evidence of
life in this meteorite will be severely impeded because it
was lying in the hot desert for probably thousands of years
and not in a relatively sterile environment such as
Antarctica, said Zipfel. However, it will give
scientists the opportunity to gain further knowledge about
geochemical processes on Mars and new insights into its
evolution as a planet.
The chemical study of Martian meteorites and their
implications for the bulk composition of Mars has a long
tradition with scientists from the Max Planck Institute for
Chemistry in Mainz. Their development of the APXS instrument
was selected by NASAs Mars "Pathfinder
Mission". Measurements with this instrument made it
possible for the first time to analyse rocks sitting on the
surface of Mars.