Craters on the surface of the asteroid 21 Lutetia. Credit: ESA
An international study reveals that asteroids have endured a multitude of impact strikes since their formation 4,565 million years ago. Scientists have reconstructed a timeline of these collisions using a physics-based model which reproduces the process through time, comparing its results with present-day information about chondrite meteorites.
The size distribution of the objects which make up the asteroid belt between Mars and Jupiter indicates that these asteroids have been struck by projectiles >20cm in size at least 100 million times. The resultant craters from these strikes are proportional to both the diameters and the velocities of these projectiles.
The information compiled on ordinary chondrites indicates that these meteorites originate from small asteroids which, with a diameter of less than a few hundred kilometres, collided, giving rise to these rocks millions of years ago. “Our work allows us to make fundamental predictions on the extent of breaking up from collisions, or the level of alteration by strikes due to impacts, which the huge majority of asteroids have experienced. It also explains the observations of the degree of alteration by strikes which appear in those chondrites which reach Earth,” notes Josep Maria Trigo, CSIC.
In Germany’s University of Braunschweig’s labs, Eike Beitz and Jürgen Blum have carried out the impact simulation experiments. Gabriela Parisi has been utilizing algorithms which reproduce the series of impacts between asteroids previously outlined, and has replicated the collisions timeline.
The model replicates external features of the asteroid, 21 Lutetia, established during the visit by the Rosetta Mission probe. This is an irregular-shaped asteroid with a major axis of 121 km. 21 Lutetia heavily cratered – one crater reaching 55km diameter- which shows clear evidence of the numerous collisions which have occurred ever since the beginnings of the planetary system. The model predicts that, as a result of fragmentation caused by large-sized projectile collisions, asteroids have huge slabs on their surfaces. The deposits of loose dust and rubble caused by this process, ie regolith, forms a surface layer a few kilometres deep. It is possible a large number of the non-differentiated meteorites, or chondrites, which have reached Earth come from these layers of regolith.
The Japanese Space Exploration Agency’s Hayabusa 2 and NASA’s OSIRIS Rex will visit 2 primitive asteroids to collect samples which they will bring back to Earth. http://www.eurekalert.org/pub_releases/2016-06/snrc-srt060216.php
Recent Comments