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Recovery of the fragments of a falling asteroid

1er mars 2009

On October the 6th, asteroid 2008TC3 was detected 20hrs before it hit the Earth. Sky surveys operated by astronomers in the entire world enable them to compute the orbit and accurately predict the fall of the object in the Nubian desert in Northern Sudan. In an articles published in Nature this week, an international team composed of astronomers from NASA and Paris observatory describe the fall and recovery of several fragments of the asteroid an dit possible linkage to another larger parent body.

It is the very first time such an event occurs. It is not uncommon that small asteroids fall on the Earth, but most of the time they remain unnoticed. Thanks to several programs of observation of meteors, astronomers can detect the very last seconds of its fall, when it is desintegrating in the atmosphere and create a streak of light in the sky. The determination of its orbit is possible but complicated. The case of 2008TC3 is different since it was observed before its fall, while still in space. Following the same idea, it is possible to determine the astronomical origin of meteorites found on the ground, by comparing how they reflect the light of the Sun to the telescope observations of asteroids. The case of 2008TC3 is unique since the mineraolgical and astronomical data are together for the first time.

Figure 1 : Quleques fragments retrouvés de la météorite Almahata Sitta. D’après Jenniskens et al (2009) Nature 458, 485

2008TC3 was 4.1m in diameter, i.e. small enough that is was not a threat for life. It desintegrated igh in the atmosphere (37km), showing its fragile nature and giving little hope to recover any fragment. However Peter Jenniskens (SETI Institute) and Muawia Shaddad went hunting the meteorites in the wilderness with a team of researchers and student from the university of Khartoum. 47 meteorites were recovered, for a total weight of 3.95kg. The analysis of the rock showed it is an atypical ureilite never observed in our collections of meteorites. So far it was associated with asteroids of class S, when 2008TC3 is of class F. Its fragile nature was a big surprise for everybody. The works of Jeremie Vaubaillon (IMCCE, Paris Observatory) based on the dynamical evolution of 2008TC3 showed that it could be linked to another larger F-type asteroid (1998 KU2, 2.6 km in diameter). The determination of the composition of extra-Terrestrial rocks fallen on the ground enables the scientists to study the origin of the Solar System. Moreover sky survey programs allows us topredict the fall of near earth asteroids. Such objects like 2008TC3 (4,1m, 80 tons) are usually harmless but the risk of seing a much larger rock falling a densily populated area is not negligeable and is taken seriously by astronomers. Paris Observatory is taking part of such an international effort.

Reference

  • Nature, 26 Mars 2009

Contact

  • Jérémie Vaubaillon
    Observatoire de Paris, IMCCE
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