Geology Reference
In-Depth Information
you stand there looking up, the further back in time you can
see as your eyes adjust to the darkness and more distant stars
are revealed. If you stand there long enough you might be lucky
and see a shooting star, an extraterrestrial body burning its way
through our atmosphere which, if it is big enough, may survive
to land here on Earth.
Meteorites hold a special place in the heart of many geolo-
gists - the only chance we shall ever have of touching some-
thing o¬-world, something alien and ancient, perhaps from
another planet - so over the years many people have analysed
meteorites and studied their chemical composition. Fritz
Paneth, whom we last encountered working in Berlin on minute
amounts of helium, at first had considerable success dating
meteorites by the helium method. Unlike terrestrial samples,
meteorites did not appear to loose helium, and some very
ancient dates were obtained. Eventually however, it was realised
that as these bodies cruised the heavens they were bombarded
with cosmic radiation that
increased
the amount of helium
present, resulting in ages that were anomalously
high
- some-
what ironic after all the problems helium had previously caused
with values being too low. Paneth and others also analysed the
chemical composition of meteorites and wondered, as Holmes
had done, about their genetic relationship to the Earth, but it
was not until 1947, just after Holmes had finished his work on
the age of the Earth using the Ivigtut galena to represent
primeval lead, that someone else suggested a better place to look
for primeval lead might be in iron meteorites.
It is sad to discover how much the final stage of dating the age
of the Earth owes to people involved in the Manhattan Project
and development of the atom bomb that killed so many thou-
sands. In the immediate aftermath of dropping the bomb on
Hiroshima, while the world waited for Japan's response to the
