The number of asteroids and comets which pass close to our planet has now passed the 10,000 mark, after the Pan-STARRS-1 telescope on the Hawaiian Island of Maui added asteroid 2013 MZ5 to the list on June 18, 2013.
Near-Earth objects (NEO) can approach within 28 million miles (45 million kms) of Earth and range from being just a few feet long up to the size of the 25 miles (40km) long 1036 Ganymed. At least 98% of the NEO’s discovered so far have been by NASA-supported surveys, and as NASA’s Near-Earth Object Program Office’s longtime manager, Don Yeomans, explains:
“The first near-Earth object was discovered in 1898. Over the next hundred years, only about 500 had been found. But then, with the advent of NASA’s NEO Observations program in 1998, we’ve been racking them up ever since. And with new more capable systems coming online, we are learning even more about where the NEOs are currently in our solar system and where they will be in the future.”
On average the NASA-instituted Near-Earth Object Observations Program discovers around three NEO’s each day, although just 10% of the NEO’s found are bigger than 0.6 miles (1 km) and thus capable of posing a global danger to our planet should one strike the Earth. Aware of the hazards, however, in 2005 NASA was tasked by Congress with cataloging 90% of NEO’s bigger than 500 feet (140m), which would subsequently help reduce the risk of an unwarned future Earth impact to just 1%. Once an NEO threat is detected in advance, the object could be then deflected using current space technologies.
As Lindley Johnson from NASA Headquarters in Washington, D.C, explains: “Finding 10,000 near-Earth objects is a significant milestone. But there are at least 10 times that many more to be found before we can be assured we will have found any and all that could impact and do significant harm to the citizens of Earth.”