Scientists discover cometary dust in Antarctic snow An EU-funded team of researchers has made the world's first ever discovery of a new group of extraterrestrial particles in central Antarctica. The work is an outcome of the ORIGINS ('Elucidating the origins of Solar System(s): anatomy of primitive meteorites') project, which h... An EU-funded team of researchers has made the world's first ever discovery of a new group of extraterrestrial particles in central Antarctica. The work is an outcome of the ORIGINS ('Elucidating the origins of Solar System(s): anatomy of primitive meteorites') project, which has received EUR 2.6 million under the Marie Curie scheme of the EU's Sixth Framework Programme (FP6). The aim of the project is to strengthen our understanding of the origins of our own planetary system as well as exo-planetary systems further afield. The findings of this latest study are published in the journal Science. The researchers from the Center for Nuclear Spectrometry and Mass Spectrometry (CSNSM) in France found the snow-bound micrometeorites. The CSNSM is part of the National Institute of Nuclear and Particles Physics (IN2P3) of the National Center for Scientific Research (CNRS). Using transmission electron microscopy, the CSNSM team discovered that the extraordinarily well preserved micrometeorites are composed of organic matter that contains tiny mineral assemblages from the most isolated and coldest regions of the Solar System. The CSNSM researchers, with logistics support from the French Paul-Émile Victor Polar Institute (IPEV) and the Italian National Antarctic Research Programme (PNRA), discovered the new particles in layers of extremely clean snow about four metres deep in the vicinity of the French-Italian scientific base Concordia, which is positioned at Dome C in central Antarctica. According to the scientists, the ultracarbonaceous micrometeorites, which are about 0.1 millimetre (mm) in size and contain between 50% to 80% carbonaceous material, are unique because no other laboratory has meteorites of this kind in its collection. Thanks to the results of this exciting research, further investigations have been initiated involving the CSNSM, the University of Lille 1, the Ecole Normale Supérieure, Paris, and the French Natural History Museum. In their analyses, the CSNSM team used an ion microprobe to show that the micrometeorites' hydrogen isotopic composition has a very high deuterium/hydrogen (D/H) ratio. 'Primitive interplanetary dust is expected to contain the earliest solar system components, including minerals and organic matter,' the authors write. 'We have recovered, from central Antarctic snow, ultracarbonaceous micrometeorites whose organic matter contains extreme deuterium excesses (10 to 30 times terrestrial values), extending over hundreds of square micrometres.' The results showed that the particles most likely stem from comets, which are relatively small bodies in the Solar System. Comets' nuclei are collections of ice, dust and tiny rocky particles. As comets draw closer to the Sun, rising temperatures trigger the massive sublimation of the icy materials. This results in an ejection of a mixture of gases and cometary grains into interplanetary space. Some dust grains may cross Earth's orbit as they move towards the Sun, and the researchers speculate that it may be some of these cometary grains that they found in central Antarctica. In their paper, the authors note that so far, only the US Stardust space mission has provided researchers worldwide with the opportunity to perform mineralogical and geochemical analyses of cometary grains. The specks of dust discovered at Concordia are similar to samples obtained from the Stardust mission. 'The masses of the particles range from a few tenths of a microgram to a few micrograms, exceeding by more than an order of magnitude those of the dust fragments from comet 81P/Wild 2 returned by the Stardust mission,' the authors write. Countries France, Italy
