Throughout our planet's 4.6 billion year history, asteroids and comets have been agents of change for our planet: they may have delivered the ingredients needed for life, and they have caused mass extinctions.
Today, asteroids spend most of their time harmlessly orbiting in the main belt between the orbits of Mars and Jupiter. These remnants from our solar system's formation can still make their way into the inner part of our solar system, however, sometimes impacting the Earth.
We now know that most of the very largest asteroids and comets that get close to Earth have been discovered, but many of the more numerous smaller ones (still capable of causing significant regional damage) remain to be found.
The Near-Earth Object Surveyor is designed to discover and characterize a large fraction of the asteroids and comets throughout our solar system, including those that get close to Earth. NEO Surveyor will not only find asteroids and comets, but it will teach us about their physical properties, origins, and evolution.
Our results suggest that the subset of NEOs that are most likely to cause impacts, the so-called potentially hazardous objects, are about twice as likely to occupy orbits in nearly the same plane as the Earth. This may mean that they are more likely to impact the Earth. With NEO Surveyor, we can better quantify the risks of asteroid impacts simply by going out and discovering them.
Late Heavy Bombardment This illustration depicts a period early in the history of the solar system in which Earth and the inner planets were pummeled by cometary debris filling the young solar system. Scientists think this "Late Heavy Bombardment" was triggered in our solar system by the migration of our outer planets, which jostled icy comets about, sending some of them flying inward. The incoming comets scarred our moon and pummeled our inner planets. They may have even brought materials to Earth that helped kick start life. (Image credit: NASA/JPL-Caltech/R. Hurt)