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Space Weathering on Mercury
By Jake Turner PTYS 395
OVERVIEW
• What is Space Weathering?• Types of Space Weathering• Effects of Space Weathering• Evidence for Space Weathering on Mercury• Future Results from MESSENGER
What is Space Weathering?
• Space weathering is a term used to describe several different processes that act on a body exposed to the space environment
• What types of objects are space weathered?
Types of Space Weathering
Sputtering
• A process where atoms are ejected from material due to the bombardment of ions.
• Believed to be the biggest factor to space weathering on Mercury
Cosmic and Solar Rays
• Nuclear effects change the isotopes.
Micrometeorite Bombardment
• Breaking up of particles (commune). – Contributes to the
amount of regolith
• Vaporization – Nanophase-Fe
• Agglutination grains get fused together.
Effect of Space Weathering
• Objects get redder with time
• Changes the depth of the absorption lines in the optical spectra.– Nanophase-iron particles
• Iron deficiently • Darkening of overall
reflectance
Evidence for Space Weathering on Mercury
• Ground observations / Kuiper Airborne Observatory– Reddened spectrum and 1 um
absorption band.– surface reflectance contrast of
Mercury is 25–35%• Mercury has more bright rays
and ejecta then the moon. – It is believed that surface mixing
weakens weathering.
Mariner 10 Evidence
• Mariner 10 confirmed the spectral differences exist on a large scare
• Less optical change at lower latitudes where the surface. temperature in daytime is higher. (confirm?)
• Maturity differences of craters
Evidence from Galileo• Colors indicate the
relative freshness of surface materials.
• Recent craters are observed in blue.
Taken by Galileo 1992 U.S. Geological Survey, Flagstaff, Ariz
Future Studies
• MESSENGER– Multi-spectral observation of the surface– X-ray spectrometer will confirm chemical
compositions including iron contents of the surface
– Determine how the change in altitude affects the amount of space weathering
– Investigate surface mixing
References
• Images are courtesy of NASA/JPL• Clark, Beth. Astronomy Department, Cornell University,
Ithaca, New York. April 9, 1996, p. 141. © 1996 American Geophysical Union
• Bryne, Shane. PTYS 411/511 Geology and Geophysics of the Solar System.
• S. Sasaki. Space weathering on Mercury. Department of Earth and Planetary Science, The University of Tokyo
• Noble and C. M. Pieters. Space Weathering on Mercury: Implications for Remote Sensing. Brown University, Dept. of Geological Sciences