Extraterrestrial Dust Found in Remote Antarctic Region

May 11, 2010

A new family of extraterrestrial particles, probably of cometary origin, has been identified for the first time in Central Antarctica. Discovered by researchers from the Center for Nuclear Spectrometry and Mass Spectrometry (CSNSM), attached to the Institut national de physique nucléaire et de physique des particules, the micrometeorites, which are remarkably well preserved, are made up of organic matter containing small assemblages of minerals from the coldest and most remote regions of the Solar System.

Melting and sieving 106 cubic feet of "ultraclean" snow that fell near a French-Italian Antarctic camp from 1955 to 1970 (before people moved in), the team discovered two micrometeorites measuring no more than .003 inches and .01 inches across, "exhibiting a fine-grained, fluffy texture with no evidence for substantial heating during atmospheric entry." 

The larger object is 85% carbon -the essential ingredient for the organic chemistry needed for life, and the smaller one is 48% carbon. Both contain higher-than-expected amounts of deuterium, a rare form of hydrogen, in a concentration 30 times higher than is usually found mixed with hydrogen on Earth -all elements common in interstellar clouds of dust in deep space, far more ancient than the sun. When the team used a microscope to examine the dust particles, says the study, they also found tiny crystals which could only have been "condensed or processed at close distances from the young sun."

The French-Italian scientific base Concordia is located at Dome C in the central region of the Antarctic continent. This is one of the most remote places in the world, where the amount of dust of terrestrial origin is extremely small.

Thanks to logistic support from the French Paul-Émile Victor Polar Institute (IPEV) and its Italian counterpart PNRA (Programma Nazionale Ricerche in Antartidea), CSNSM (Centre de spectrométrie nucléaire et spectrométrie de masse) researchers have discovered a new family of extraterrestrial particles in layers of ultra-clean snow located at a depth of four meters in the vicinity of the base.

Comets are made up of a mixture of icy materials and dust. Occasionally, some of them enter the inner Solar System. When they pass near the Sun, the rise in temperature causes massive sublimation of the icy materials, leading to an ejection of a mixture of gases and cometary grains into interplanetary space. Some dust grains may cross Earth's orbit as they drift towards the Sun, where most of them finish their journey. It is probably some of these cometary grains that the CSNS scientists discovered in Antarctica.

Until now, only the US Stardust space mission had enabled international teams to carry out mineralogical and geochemical analysis of cometary grains. The micrometeorites discovered at Concordia show numerous similarities to the samples from the Stardust mission.

For the first time, they allow scientists to study extremely well preserved assemblages of minerals and organic material that were present beyond Jupiter's current orbit at the time when the Sun and the planets were being formed. Their chemical and isotopic composition should make it possible to comprehend the physical and chemical processes at work inside the disk of gas and dust that surrounded the early Sun 4.5 billion years ago.

Casey Kazan via materials provided by CNRS published in the Journal of Science.