Vision and Voyages for Planetary Science in the - Solar System ...

• Which classes of asteroids participated in the late heavy bombardment of the inner planets
and the Moon, and how did the current population of asteroids evolve in time and space?
• What are the sources of asteroid groups (Trojans and Centaurs) that remain to be explored by
spacecraft?
• How are objects delivered from the Kuiper belt to the inner solar system? Specifically, by
what mechanisms are Jupiter family comets resupplied to the inner solar system?
Future Directions for Investigations and Measurements
Determining the orbits of vast numbers of KBOs presents an unprecedented opportunity to
reconstruct the early dynamic history of the solar system. Orbital surveys coupled with determination of
physical characteristics can constrain physical conditions in the nebula. Missions to Trojan or Centaur
objects could provide information on their sources, as well as basic characterization and are important
goals for the future.
INTERCONNECTIONS
To Other Parts of the Solar System
Mixtures of meteorite chemical compositions are commonly used to construct models of the bulk
compositions, volatile inventories, and oxidation states of the terrestrial planets. Radioactive isotopes in
meteorites provide the necessary foundation to construct timescales for planet formation. Differentiated
asteroids and iron meteorites provide insights into core formation in the terrestrial planets. Resolving the
debate concerning the compositions (and likely origins) of the martian moons Phobos and Deimos may be
relevant to understanding the early history of Mars. The orbital distributions of primitive bodies constrain
models for the orbital migrations of the giant planets in early solar system history. Cosmic element
abundances, determined in part from chondritic meteorites, provide a baseline for comparison with the
atmospheric compositions of Jupiter and Saturn. Prebiotic chemistry, as understood from organic matter
in primitive bodies, is a starting point for life on Earth and for the study of astrobiology.
To Extrasolar Planets
Studies of the sizes, orbital distributions, and compositions of the KBO population and of
interplanetary dust derived from KBOs, comets, and asteroids provide critical data for interpreting
accumulating data on debris disks around stars such as Beta Pictoris and Fomalhaut.
Other
The isotopic compositions of presolar grains in meteorites and interplanetary dust particles
provide tests of theoretical models of nucleosynthesis in stars and supernovae, which are of great interest
to astrophysics. The mineralogy and physical properties of presolar grains also are useful in interpreting
astronomical observations of dust in the interstellar medium. The measured abundances of short-lived
radionuclides in meteorites reflect the formation of our Sun in the vicinity of high-mass stars that injected
supernova materials into the nebula, in agreement with astronomical observations of star-forming regions.
The discovery of chondrules and refractory inclusions in comet material returned by the Stardust mission
has motivated models of large scale mixing in dust disks. The Kuiper belt offers a model for telescopic
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