The latest calculations from NASA say that they have identified 90% of the “near-Earth asteroids”, those whose orbits bring them to within 28 million miles of earth (45 million km), that could be capable of producing planet-wide catastrophes. In 1998, Congress mandated that NASA find 90 per cent of asteroids in this category.
Calculations using observations made by the recently retired WISE (Wide-field Infrared Survey Explorer) telescope, shows that 911 of an estimated 981 near-Earth objects over one kilometre in size have been discovered. None are thought likely to hit Earth.
And these are only the really big asteroids. If we include the medium-sized objects, the estimated number jumps up 19,500. This sounds like a lot, and it is, but it actually is significantly less than we previously estimated. In an analysis to appear in the Astrophysical Journal, there must be roughly 19,500 midsize NEAs (with diameters between 100 m and 1 km), far fewer than the pre-WISE estimate of 35,000.
Though our progress sounds pretty good up to now, in 2005, that 90% goal was extended to include 90% of asteroids down to 140 meters in size — and NASA is nowhere near there yet.
And don’t for a second think that this is a waste of money, we are preventing a Deep Impact style situation here! There is even a planetary defense agency, showing that there is at least someone looking up and taking these threats seriously.
In fact, asteroid exploration has been a priority of US president Barack Obama and has boosted efforts on planetary defense and near-Earth asteroid discovery. In October 2010, the White House Office of Science and Technology Policy assigned NASA as the lead agency on planetary defense. Someone’s got to do it, right?