Concordia
Station, a French-Italian research project run by the "Institut
français pour la recherche et la technologie polaires"
(IFRTP, French Polar Research and Technology Institute) and its Italian
counterpart, is located in one of the world's coldest, driest deserts,
in central Antarctica. Isolated from terrestrial dust and with its
snowy surface separated from the underlying rock by 4 kilometers of
ice, the station is ideal for the search of extraterrestrial dust.
According
to the Early MicroMeteorite Accretion (EMMA) scenario proposed by
Michel Maurette of the CNRS, micrometeorites played an important role
in atmospheric and oceanic formation and in the apparition of life
on Earth. Micrometeorites that landed in Antarctica are revealing
their secrets following an expedition conducted in January 2000. A
few micrometeorite grains were collected near Concordia by melting
snow and then filtering it under ultra-clean conditions using apparatus
developed in collaboration with the Chaffoteaux & Maury group.
The CNRS "Centre de Spectrométrie Nucléaire et
de Spectrométrie de Masse" (CSNSM, Center for Nuclear
Spectrometry and Mass Spectrometry) group, in association with Professor
Géro Kurat from Vienna's Natural History Museum and Dr. John
Bradley from MVA-Inc, USA, have studied their mineralogy. This first
collection of extraterrestrial dust collected at Concordia enabled
the team to establish a lower limit of 6,000 tons of micrometeorites
that reach the Earth's surface annually.
First
observed by M. Maurette in 1987, micrometeorites are interplanetary
dust particles with diameters ranging from 25 up to 500 mm. They do
not melt during atmospheric entry. The team is currently seeking to
establish the existence of refractory phases formed during the birth
of the solar system. Analysis to determine the presence of descendants
of radioactive isotopes formed at the time and "frozen"
in the refractory phases will then be undertaken. The results should
provide further insight into irradiation phenomena occurring in the
primitive solar system.
The
total amount of more recently formed radioactive isotopes in the micrometeorites
will be assessed by the accelerator mass spectrometry team at the
Gif-sur-Yvette Tandetron accelerator to determine the recent irradiation
of the dust as it travelled from its parent body (comet and/or asteroid).
