NEAR EARTH ASTEROIDS: A CLASSIFICATION SYSTEM ACCORDING TO THEIR SHAPES.

ACEVEDO, R.D.; ROCCA, M.; RABASSA, J; PONCE, J. F.; STINCO, SERGIO

Cairns

Congreso; 75th Annual Meteoritical Society Meeting; 2012

Meteoritical Society Meeting

NEAR EARTH ASTEROIDS: A CLASSIFICATION SYSTEM ACCORDING TO THEIR SHAPES. R. D. Acevedo1, M. Rocca2, J. Rabassa1,3, J. F. Ponce1 and S. Stinco3. 1CADIC-Conicet, Ushuaia, 9410, Argentina. E-mail: acevedo@cadic-conicet.gob.ar 2CABA, Argentina. 3Universidad de Tierra del Fuego, Argentina. 4Neuquén, Argentina. Introduction: A new way to classify Near Earth Asteroids (NEAs) according to their shapes is proposed. This classification is based on the asteroid roundness and sphericity in the same way that it is used in geological sciences to describe clasts in mechan-ical sedimentary rocks. This classification system was applied to eight NEAs for which a reliable shape form is known. Results: Using the Powers? Scale of Roundness [1], illustra-tions of known asteroids can be seen in the comparative chart: Abstracting from the size, the classification of Pettijohn [2] can be easily applied to the Near Earth Asteroid?s shapes as shown the roundness index in the figure below: Conclusions: From our analysis results it may be said that, following the knowledge of rock particle evolution, the more rounded the shape of NEAs is then the larger the time it has been exposed in the interplanetary space medium. Thus, according to their shapes, angular NEAs are undoubt-edly younger sharp fragments ejected in relatively recent times from larger bodies. Likewise, rounded bodies are older fragments that have stayed for a long period of time in the interplanetary medium. References: [1] Powers M.C. 1953. Journal of Sedimentary Geology, 23: 117-119. [2] Pettijohn F. J. 1949. Sedimentary Rocks. Harper & Bros, New York. 75th Annual Meteoritical Society Meeting (2012) 5043.pdf