Christian Koeberl is a professor of Impact Research and Planetary Geology at the University of Vienna and an Asteroid Day Expert. In this post, he answers a user-submitted question. Do you have an asteroid related question? Submit it here.
Many countries have asteroid/comet impact craters, but it seems there is no crater known in Spain. Is Spain a safe place? Or did people not yet look for craters? Or is the erosion faster than in other countries?
Christian Koeberl answers:
There are many countries on Earth – and huge parts of the surface of our planet – that do not “have” an impact structure. On a map of the distribution of impact craters on Earth one clearly sees that the CONFIRMED impact structures are not homogeneously distributed on our planet. This is the result of a complex interplay of geological and also human factors that affect the preservation and discovery of impact craters on Earth, even though they form randomly across the Earth. The are are several issues that need to be considered:
a) the age of the continental crust (the older the more likely that it contains evidence of an impact event);
b) geological processes can lead ...