Incoming asteroids could crumble before impact

摘要

Rocks that fall from space may be less than solid. It seems that many asteroids are weak and brittle -though this is not necessarily good news for us here on Earth. More than 90 per cent of asteroids and comets larger than a kilometre across in Earth's neighbourhood have already been discovered, and we think the region is mostly clear. Yet should one wander near to us, it could have devastating results. We have ideas about how to push it away with thrusters or solar sails, but the success of such schemes depends on understanding what the rocks are made of and whether they might break apart.