Space weathering of planetary regoliths.

摘要

This dissertation is an experimental study on how radiation processes affect the surfaces of bodies in the solar system. The analytical techniques are visible/infrared spectroscopy, mass spectrometry, x-ray photoelectron spectroscopy, microgravimetry, and scanning electron microscopy. The irradiation techniques are ion irradiation, laser irradiation and UV photolysis.; In the Interstellar Medium, the solid CO2/CO ratio is ∼10 4-5 times higher than expected suggesting that solid CO2 is formed on the grain surface. We find that irradiation of solid CO cannot produce enough CO2 to explain this discrepancy.; The Galileo Near Infrared Mapping Spectrometer detected H2O 2 on Europa. Using 100 keV protons, we show that H2O 2 can be produced from H2O in the same abundance as has been detected.; The thermal evolution of comets is likely heavily dependent on their irradiation history. We investigated this problem by following the thermal evolution of a H2O, H2O2, O2, and O3 mixture created by irradiating solid H2O 2 with 50 keV H+. We find that most of the radiolytically produced O2 remains trapped until ∼155 K, unlike previous experiments on unirradiated mixtures.; Recently the Cassini spacecraft detected plume of water vapor, nitrogen and icy particles emitting from the south polar region of Enceladus, reinforcing its putative geologic activity. We show that similar behavior results when we warm ion irradiated ammonia-water ices to temperatures found on the South Pole (∼130 K).; The Near Earth Asteroid Rendezvous spacecraft landed on the surface of asteroid 433 Eros. Compositional measurements reveal that its surface is depleted in sulfur, which is believed to be a result of solar wind and micrometeorite bombardment. Our results of ion irradiation and ns pulsed laser irradiation (simulating micrometeorite impacts) on FeS indicate that these two processes together may be responsible for this depletion.; Ordinary chondrite meteorites are believed to originate from S-type asteroids, even though there is a significant spectral difference between the two. We have studied the effects of ion bombardment and ns pulsed laser irradiation on minerals found on these objects.{09}We show that ion and laser irradiation of olivine as well as impact induced vapor redeposition are effective mechanisms for space weathering.