Asteroids are rocky bodies up to 1000 km in diameter which originated in the inner solar system. Most reside in the asteroid belt between Mars and Jupiter and represent the remnants of the population of planetesimals that were not incorporated into terrestrial planets, because of the gravitational influence of Jupiter.
Near-Earth Objects (NEOs) are small solar system bodies that have perihelia within 1.3 AU and therefore can approach the Earth within a few tenths of an astronomical unit. A subset of these, the Potentially Hazardous Asteroids (PHAs) are defined as having minimum orbit intersection distances with the Earth of 0.05 AU or less, (and diameters larger than 100 m). NEOs may be asteroidal (NEAs), or cometary (NECs). Over 1600 NEAs and 40 (periodic) NECs are currently known. The population larger than 100 m in diameter probably exceeds 100,000 objects, less than 2% of which have been discovered.
NEAs provide a link between meteorites and the interiors of their parent bodies in the main asteroid belt. Some are relatively unaltered, providing clues to conditions in the early solar nebula, whereas other have undergone a variety of aqueous, thermal and collisional processing.
NEAs are the largest Earth impactors that, historically, have profoundly affected the Earth's climate and biology.
Asteroid research in PSSRI includes ground-based observational programmes and space mission studies and is focussed on NEOs. In addition, we undertake a wide range of laboratory studies of
meteorites, from which the origin and evolution of their parent bodies is investigated and study the role of large scale impacts on terrestrial geological and biological processes.
