Asteroids have the ability to tell us a lot about how our Solar system formed. Because they lack atmospheres and weather, they remain largely unchanged since the time of their formation, altered only by impacts with other bodies. Another aspect of asteroid study is that of planetary defense. There are a fair number of asteroids, particularly Apollos, that pose a potential threat to the Earth. Most scientists consider any asteroid larger than 1 km in diameter with an Earth crossing orbit a potential global killer. The last time that the earth was struck by an asteroid of this size was at the site of the Chicxulub crater, and resulted in the destruction of 75% of the species on the planet. It behooves us, therefore, to keep an eye to the sky as earlier detection of an impact will give us more time to attempt to avert it.
