Here is a view of the Barringer Crater from space. The Crater was originally called Diablo Canyon Crater, then re-named the Barringer Crater after the man who first proposed that this was an impact crater, not a volcanic one.
It was not until Eugene Merle Shoemaker and his research came along in 1963 that it was conclusively shown to be an asteroid impact crater.
Scientists at the University of Arizona's Spacewatch Project are using the telescope at Kitt Peak, outfitted with modern anti-blur video sensors, to scan the skies and track as many asteroids as possible. Here is a video describing their efforts, from Space.com . There are many other such impact craters on the Earth, and it is very likely that there are many asteroids out in our Solar System that could easily strike the Earth. After all, our planet is upwards of 5 Billion years old. Our Sun has at least 10 Billion more years of nuclear fuel left. We humans could be very lucky to have evolved into our modern civilization in the relatively short time span between asteroid impacts. There are many catastrophes that we can do nearly nothing about. Earthquakes are unpredictable and uncontrollable. The same goes for massive volcanic eruptions. Asteroid impact, no matter how far-fetched it may sound, is not just possible, it is probable, and it is the one thing that we can have advance warning of in time to actually do something about it. These things are HAULING MAJOR ASS through the Solar System, and an impact would wipe out almost all life as we know it.
Based on crater formation rates determined from the Earth's closest celestial partner, the Moon, astrogeologists have determined that during the last 600 million years, the Earth has been struck by 60 objects of a diameter of five kilometers or more. The smallest of these impactors would release the equivalent of ten million megatons of TNT and leave a crater 95 kilometers across. For comparison, the largest nuclear weapon ever detonated, the Tsar Bomba, had a yield of 50 megatons.