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