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 © 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