Nanoindenting the Chelyabinsk Meteorite to Learn about Impact Deflection Effects in asteroids

1Carles E. Moyano-Cambero, 2Eva Pellicer, 1Josep M. Trigo-Rodríguez, 3Iwan P. Williams, 4Jürgen Blum, 5Patrick Michel, 6Michael Küppers, 1Marina Martínez-Jiménez, 1Ivan Lloro, 7Jordi Sort
The Astrophysical Journal 835, 2 Link to Article [https://doi.org/10.3847/1538-4357/835/2/157]
1Institute of Space Sciences (IEEC-CSIC), Meteorites, Minor Bodies and Planetary Sciences Group, Campus UAB Bellaterra, c/Can Magrans s/n, 08193 Cerdanyola del Vallès (Barcelona), Spain
2Departament de Física, Universitat Autónoma de Barcelona, E-08193 Bellaterra, Spain
3School of Physics and Astronomy, Queen Mary, University of London, 317 Mile End Road, E1 4NS London, UK
4Institut für Geophysik und extraterrestrische Physik, Technische Universität Braunschweig, Mendelssohnstr. 3, D-38106 Braunschweig, Germany
5Lagrange Laboratory, University of Nice, CNRS, Côte d’Azur Observatory, France
6European Space Agency, European Space Astronomy Centre, P.O. Box 78, Villanueva de la Cañada E-28691, Spain
7Institució Catalana de Recerca i Estudis Avançats (ICREA) and Departament de Física, Universitat Autónoma de Barcelona, E-08193 Bellaterra, Spain

The Chelyabinsk meteorite is a highly shocked, low porosity, ordinary chondrite, probably similar to S- or Q-type asteroids. Therefore, nanoindentation experiments on this meteorite allow us to obtain key data to understand the physical properties of near-Earth asteroids. Tests at different length scales provide information about the local mechanical properties of the minerals forming this meteorite: reduced Young’s modulus, hardness, elastic recovery, and fracture toughness. Those tests are also useful to understand the potential to deflect threatening asteroids using a kinetic projectile. We found that the differences in mechanical properties between regions of the meteorite, which increase or reduce the efficiency of impacts, are not a result of compositional differences. A low mean particle size, attributed to repetitive shock, can increase hardness, while low porosity promotes a higher momentum multiplication. Momentum multiplication is the ratio between the change in momentum of a target due to an impact, and the momentum of the projectile, and therefore, higher values imply more efficient impacts. In the Chelyabinsk meteorite, the properties of the light-colored lithology materials facilitate obtaining higher momentum multiplication values, compared to the other regions described for this meteorite. Also, we found a low value of fracture toughness in the shock-melt veins of Chelyabinsk, which would promote the ejection of material after an impact and therefore increase the momentum multiplication. These results are relevant to the growing interest in missions to test asteroid deflection, such as the recent collaboration between the European Space Agency and NASA, known as the Asteroid Impact and Deflection Assessment mission.

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