Giant impacts and the formation of terrestrial planets
by
Willy Benz(University of Bern)
→
Europe/Stockholm
FA31
FA31
Description
Once planetesimals a few kilometers in size are formed in the
proto-planetary nebula, their collisional evolution leads to the
formation of bodies of increasing sizes. As their masses grow,
gravitational scattering leads to higher random velocities and therefore
to more and more energetic collisions. Towards the end of the process,
when bodies reach planetary sizes and collide with velocities equal or
even larger than their own escape velocity, the energy involved in such
events becomes so large that they can dramatically affect the planets
themselves. It is argued that signatures of such energetic events are
still visible in the present day solar system.
The Moon, for example, is currently thought to have formed from the
debris of such an event that involved the proto-Earth and a body about
1/10 of its mass. Another compelling case for a giant impact can be made
for Mercury. In this case, the collision is invoked to blast away a
significant fraction of the mantle in order to explain the unusually
high mean density of the planet. Host: Garrelt Mellema
