
Green: Known asteroid locations in inner solar system. Yellow: Near Earth Asteroids nearing earth. Red: Potentially Hazardous Asteroids that cross earth's orbit.
NEAs and PHAs
Space photography has recent advances showing shocking information. "Our team was surprised to find the overabundance of low-inclination PHAs," (Amy Mainzer/NASA/Jet Propulsion Lab). In other words, some asteroids are making closer approaches to earth than once thought. Mainzer, leader of the WISE asteroid-hunting mission, has used the NEOWISE project for all asteroid predictions.
Near-Earth Asteroid (NEA) orbits are closest to earth's orbit. Some NEAs' orbits intersect earth's, and a future collision with earth may exist. Thousands of NEAs exist. Estimates of kilometer-size asteroids are (+/-) 2000. [largest: 1036 Ganymed, at 32km.]