| Description: | It is only since the Apollo 11-17 moon sample return missions in the 1970-ies that it is fully realized that the numerous craters seen on the moon (and Mercury for that matter) are caused by impacts of minor planets (asteroids and comets) rather than by volcanism. It is only since the late 1990-ies that optical surveys allow a definitely increasing knowledge of Near-Earth Objects (NEOs) presence. In recent years data and models indicate that NEOs with sizes larger than 40 meter can be potentially hazardous for the Earth on a local scale. Both the impactors of Meteor Crater in Arizona ( a nickel-iron asteroid impact, 50,000 yr ago) and the Tunguska event in Siberia (a stony asteroid exploding in the air, 103 yr ago) probably had diameters of ~ 40 meter. The colloquium will present some of the 65 million year old history of the topic and some prospects. It emerges that, if we do not want to be bothered by NEOs, we have to do something about them.
Image Caption: Once upon an asteroid |
