Mechanical properties of particles from the surface of asteroid 25143 Itokawa

¹ Institute of Space Sciences (ICE-CSIC), Campus UAB, C/Can Magrans s/n, 08193 Bellaterra (Barcelona), Catalonia, Spain
e-mail: tanbakouei@ice.csic.es
² Institut d’Estudis Espacials de Catalunya (IEEC), C/Gran Capità, 2-4, Ed. Nexus, desp. 201, 08034 Barcelona, Catalonia, Spain
³ Departament de Fisica, Universitat Autònoma de Barcelona, 08193 Bellaterra, Catalonia, Spain
⁴ Institució Catalana de Recerca i Estudis Avançats, Passeig Lluís Companys 23, 08010 Barcelona, Catalonia, Spain
⁵ Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Lagrange Laboratory, France
⁶ Institut für Geophysik und extraterrestrische Physik, Technische Universität Braunschweig, Mendelssohnstr. 3, 38106 Braunschweig, Germany
⁷ Department of Earth Science, Graduate School of Science, Tohoku University, Japan
⁸ School of Physics and Astronomy, Queen Mary, University of London, Mile End Rd. London E1 4NS, UK

Received: 28 February 2019
Accepted: 10 July 2019

Abstract

Aims. Asteroids have been exposed to impacts since their formation, and as a consequence their surfaces are covered by small particles, pebbles, and boulders. The Japanese JAXA/ISAS Hayabusa mission collected micron-sized particles from the regolith of asteroid 25143 Itokawa. The study in terrestrial laboratories of these particles provides a scientific opportunity as their physical properties can be compared with those characteristic of chondritic meteorites that are often considered proxies of the building materials of potentially hazardous asteroids (PHAs).

Methods. Here we present the results from a study of the mechanical properties of three of these particles using a precise technique called nanoindentation. The derived results are compared with those obtained via a methodology similar to that used for the Chelyabinsk meteorite.

Results. The reduced Young’s modulus values obtained for the Itokawa samples are higher than those measured for the Chelyabinsk chondrite, so these specific particles of asteroid regolith are more compacted than the minerals forming the particular LL chondrite associated with PHAs. This might be a natural consequence of particles surviving long exposure times on the surface of a (near-Earth asteroid) NEA. The Double Asteroid Redirection Test (DART) mission plans to excavate a crater in the surface of the (65803) Didymos satellite. Our results suggest that excavating a crater with a kinetic impactor in an area of significant fine-grained regolith will increase the momentum transfer. As this will facilitate the release of particles carrying target mass in the opposite direction to the movement of the projectile, there is no need to grind up the target during the mechanical excavation phase.