Several thousands of tonnes of extraterrestrial
material fall onto the surface of the Earth
every year!!!
Our Solar System
Most of this material is just clusters of dust grains weighing less than 10 grams
each, but ~4500 meteorites weighing at least a kilogram each falls every year.
Most meteorites come from the asteroid belt that orbits the Sun between
Mars and Jupiter, but there are also meteorites that come from Mars and the
Moon.
The asteroid belt
An asteroid is rocky object in space that can be a few
metres wide to several hundred kilometres wide.
But why are meteorites so hard to find?
Most meteorites land in the oceans and are therefore never found. 71% of the
Earth’s surface area is covered by oceans.
It can also be tricky to easily tell the difference between true meteorites and
normal Earth rocks: “meteowrongs”.
Earth – “the water planet”
Where are the best hunting grounds
for meteorites?
Most meteorites are found in areas that are free of
vegetation and sparsely populated, such as the Sahara
desert and in the Antarctic ice sheet.
Every year, scientific expeditions set out to search for
meteorites in Antarctica. The samples they collect are then
carefully catalogued and stored in museums and in the
NASA Antarctic meteorite collection, where they become
available for loans and further studies by meteorite
scientists all around the world.
Meteorite hunting in Antarctica - a cold desert
Hot and cold deserts are the best
places to search for meteorites
Image courtesy of Peter Jenniskens (SETI Institute/NASA Ames)
Meteorite Almahata Sita
Nubian Desert, Sudan
Fresh dark meteorites are much easier to spot against the desert
sand or in the Antarctic ice. Also, the lack of water in hot and cold
deserts slow down chemical weathering. This means that meteorites
which fall in deserts can survive for long periods, and therefore may
accumulate over time. Several hundred new meteorites have been
discovered in e.g. the Nullarbor Plain desert in Australia, by
expeditions led by Dr Phil Bland, Imperial college, London.
This event is funded by the Science & Technology Facilities Council,
the Royal Society of Edinburgh and the University of Glasgow.