Physics
Scientific paper
May 2002
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2002agusmsh22b..03c&link_type=abstract
American Geophysical Union, Spring Meeting 2002, abstract #SH22B-03
Physics
6025 Interactions With Solar Wind Plasma And Fields, 6045 Physics And Chemistry Of Materials, 2104 Cosmic Rays, 2114 Energetic Particles, Heliospheric (7514), 2124 Heliopause And Solar Wind Termination
Scientific paper
Cometary bodies with perihelia beyond the orbit of Jupiter accumulate dark mantles from cosmic ray irradiation faster than such material can be lost by ice sublimation from solar heating. Impacts by interplanetary grains mix irradiated material on surfaces of these bodies to meter depths, while impacts of larger bodies can produce major resurfacing with coverage by brighter ices from deeper layers. Due to solar modulation of galactic cosmic rays the irradiation environment is likely very different outside the known heliosphere now probed by Voyager 1 measurements out to 85 AU. The more equatorial population of Kuiper Belt Objects (KBOs) extends from Neptune's orbit at 30 AU out to thousands of AU, beyond which lies the spherically symmetric population of Oort Cloud comets at 10,000 to 100,000 AU. Thus the KBO and Oort Cloud comets span the full range of irradiation environments inwards from and beyond the solar wind termination shock, within the heliosheath, near the heliopause, and in the local interstellar medium (VLISM). Scattered KBOs on highly eccentric orbits extending out to 1000 AU traverse multiple environments. Only models suggest where these outer boundaries and regions are, since Voyager 1 has not yet encountered them. An expected increase in pickup and accelerated ions at keV to MeV energies, at and beyond the termination shock (somewhere beyond 85 AU), would increase irradiation rates, as would the unmodulated cosmic ray fluxes of the local interstellar medium. Pioneer measurements first showed that interplanetary dust extends far beyond the asteroid belt and the orbit of Jupiter, and a more recent report from Ulysses indicates that KBOs are the likely sources of this extended dust cloud. Combinations of irradiation and dust impact processes in different regions may variously drive the evolution of surface chemistry on comets of the outer solar system over time scales of millions to billions of years as estimated from available models for fluxes of cosmic rays and interplanetary dust. Expanding spectroscopic surveys of surface composition for KBO's from Earth, the ongoing Voyager measurements, and proposed future missions to the outer heliosphere and beyond (e.g., New Horizons, Interstellar Probe) should be planned for improved understanding of these complex and spatially variable interactions between KBOs and the local environments.
Christian Eric R.
Cooper John F.
Johnson Robert E.
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