Small Bodies

Small bodies are believed to be the primordial building blocks of the planets. The principal reservoirs of the small bodies are the asteroids (main-belt and near-Earth), the comets, the Centaurs, the Kuiper belt objects and the comets of the Oort Cloud. Small bodies are especially important in planetary science for two reasons. First, most small bodies have escaped wholesale melting or other severe forms of thermal processing and thus preserve chemical compositions closer to the initial ones. [In fact, many small bodies (e.g. the comets) formed and remained so cold over cosmic time that they retain the volatile ices from which they formed]. Second, the small bodies are very numerous compared to the major planets. They make excellent dynamical tracers and allow detailed models of the origin and evolution of the solar system to be tested.

 

Main Asteroid Belt and Trojan Asteroids

Oort Cloud and Kuiper Belt

Studies

Near-Earth asteroids represent an impact threat but also an opportunity to conduct investigations from the Earth that are impossible on more distant targets.  Radar studies and optical lightcurves show that many near-Earth asteroids are binaries, raising interesting questions about their origin and survival. (Jean-Luc Margot, Michael Busch, Julia Fang, Shantanu Naidu)
Some asteroids in the main-belt between Mars and Jupiter have recently been found to show comet-like behavior, ejecting dust from their surfaces and sporting cometary comae and tails.  Some of these appear to be activated by the sublimation of water ice (i.e. they are compositionally comets).  These objects were either formed in-place or, perhaps, captured from the Kuiper belt long ago.  They may represent survivors of a now-depleted population that could have supplied some of the Earth’s water. (David Jewitt)
Other active asteroids are produced by collisions which, in the main-belt, occur with relative speeds of several kilometers per second and are therefore explosive (NASA movie)  Being able to observe on-going collisions opens the door to the study of hypervelocity impact in the real world, and should have important ramifications for dust production in the solar system and in the debris disks of other stars. (David Jewitt, Michal Drahus)
Although quite large, asteroid 4 Vesta is another “small body” asteroid, made special by the visit of the ion-powered DAWN spacecraft.  A UCLA investigator leads the mission, while others explore the nature of the surface from high resolution images. (Chris Russell, Jennifer Scully)
Beyond Neptune lies the Kuiper belt, a repository of primordial solar system matter that feeds a steady stream of comets into the inner solar system.  On-going investigations study the comets and the Kuiper belt objects themselves. (David Jewitt, Aurelie Guilbert-Lepoutre, Michal Drahus, Hilke Schlichting, Rachel Stevenson)

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