Asteroid 2005 YU55, (for the year and month when it was discovered) passed near the Earth- closer than the moon- on November 8, 2011, as reported at http://www.cnn.com/2011/11/08/opinion/urry-asteroid-earth-risk/?hpt=hp_bn9. This asteroid posed no threat this time. However, a large asteroid hitting the Earth could cause global catastrophe. So, as Meg Urry, Israel Munson professor of physics and astronomy and chairwoman of the department of physics at Yale University, points out NASA has a Near Earth Object Program to track potential collisions.
Vesta is much smaller than the asteroid that created Chicxulub- the crater near the Yucatan that is reported to have caused the mass extinction of the dinosaurs- but it could damage a city or cause a tsunami. Scientists are studying how to prevent a collision if an asteroid were found to be on course with the earth; they would need to alter its trajectory somehow.
NASA's WISE infrared satellite suggest there are roughly 500,000 near-Earth objects with diameters of 50 to 100 meters with an estimated impact frequency of one every thousand years. “Scientists think the famous Tunguska event of 1908, an enormous explosion that flattened 80 million trees over 830 square miles (2/3 the size of Rhode Island) in Russia, was caused by an impact from an asteroid or meteorite about 50 to 100 meters in diameter. The force of this explosion was roughly 1,000 times larger than the nuclear bomb dropped on Hiroshima.”
In severe budget cutting times, how much money will be reserved to continue studying asteroids? How big of an issue is it to protect the planet? Can we afford to not pay attention or are other problems more pressing- like will our population increase sooner doom human life on earth? As someone who studies natural hazards, I find it interesting that impacts with extraterrestrial objects can strike the earth anywhere- there are no regions at higher or lower risk than others and the potential impacts will be global, when a big one eventually hits. The pitted moon is our visual reminder that it is only a matter of time. Meanwhile we’ll continue to cope with the impacts of all the other natural hazards affecting our dynamic earth. Vesta is another reminder of what is to come eventually.