Ettore Perozzi is a planetary scientist working on celestial mechanics and space mission design. He is presently involved in Asteroid hazard monitoring at the ESA Near-Earth Object Coordination Centre (ESRIN, Frascati, Italy). Throughout his career education and public outreach has always represented a major interest leading to the publication of articles and books on popular astronomy. The Italian edition of the book “Celestial Mechanics – Waltz of the Planets” (co-authored with Alessandra Celletti, Springer-Praxis 2007) has been awarded the Galileo Prize for scientific literature in 2008; his illustrated books for kids “Il Cielo Sotto la Terra” (Lapis 2005, 2011) has been translated into several languages. Many public conferences have been delivered on subjects ranging from the human exploration of the solar system to updating the link between astronomy and music (Rock Around the Planets). He is a founder member of the “asSaggi Science Bookshop” (Via degli Etruschi 4, Roma, Italy – www.libreriaassaggi.it). Asteroid number 10027 bears his name.
AVOIDING THE FATE OF THE DINOSAURS
The asteroid hazard after Chelyabinsk: new solutions for an old problem
In the comic strip series “Asterix the Gaul”, the occupants of the little village on the Armorican coast who are used to drink a potion giving superhuman strength, are scared of nothing except of the sky falling on their heads. Long before, the dinosaurs, which were ruling life on our planet since almost two hundred million years, had no anticipation that they were soon to be wiped out by a celestial body fallen from the sky. This gives a good representation of the human perception of the asteroid hazard, oscillating between panic and underestimation. Yet what happened on 15 February 2013 early morning over the Russian city of Chelyabinsk, when a space rock about 18m in diameter entered the Earth atmosphere exploding at some 20 km of altitude represented a challenge for both scientific research and science communication. Reality was broadcasted worldwide almost in real time through the social media calling for new answers to the old questions. How come that no-one saw it coming? Not even when the present Near Earth Asteroids discovery rate has reached an astounding 1000 objects per year (that is as many as during the whole century after the discovery of Eros, the first Earth crossing asteroid)? What about if the Chelyabinsk superbolide were of a larger size? Are we at risk of sharing the fate of the dinosaurs? Were the Gauls quite right, after all? Answering these questions means to enter the subtleties of asteroid hazard, tackling probabilistic issues and learn from statistics that unusual events do indeed happen.