Thermal Weathering on Airless Planetary Surfaces

Details Thermal Weathering on Airless Planetary Surfaces Thermal Weathering on Airless Planetary Surfaces

Dec 2009

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009agufm.p23c1289p&link_type=abstract

American Geophysical Union, Fall Meeting 2009, abstract #P23C-1289

Biology

[5415] Planetary Sciences: Solid Surface Planets / Erosion And Weathering

Scientific paper

All airless planetary surfaces in our Solar System appear to be covered by a regolith layer. There are several general processes that could form such a regolith layer, including the rain of impactors on the surface, mass wasting, sublimation degradation, and physical weathering by thermal changes. Several of these processes have been well studied on icy satellites [e.g. Moore et al. 1999]. Weathering of craters and regolith generation on airless bodies are presumed to result from micrometeorite impacts. For instance, one could look at examples of smooth terrain on the moon and try to explain smooth terrain on Callisto by small impacts, but the crater density is well below equilibrium. This led Moore et al. (1999) to state, “…some other process is dominating its surface layer.” The question is: what process could this be? Moore et al. (1999) argue that sublimation and deposition is a dominant weathering process occurring on Callisto, but it may not be the only regolith-generating process. Vance et al. (2007) adapted a thermal expansion anisotropy and mismatch driven fracturing model for a matrix of square grains. Recently we have been looking at the stress at grain boundaries in this model. This stress term is dependent on the grain size and rate of temperature change at the surface of the body. The question we are trying to answer is whether the stress generated at grain boundaries during diurnal heating and cooling is enough to generate and propagate fractures in the surface material. We started by developing a one dimensional finite difference thermal model for the near-surface environment on an airless body, insulated on the bottom boundary and driven by insolation and radiation to space on the surface. We also assumed that density was constant with depth. The program can take the different parameters for each body (e.g. the bolometric albedo and distance from the sun) and calculate the temperature change at any depth over a diurnal cycle at any latitude. Ice is a simple material to consider in models of thermal weathering. We have developed a thermal model for airless planetary surfaces in our Solar System. By linking this thermal model to the grain boundary stress model, we are able to place limits on the smallest grain size that permits thermal weathering, and the depth to which cracking will occur on different icy bodies in our solar system. For instance, we found that cracking can occur on the surfaces of Ganymede and Callisto for grain sizes > 0.5 microns. Thermal weathering may be an important process contributing to regolith generation on airless planetary surfaces. This near-surface process may help to speed up other processes like mass wasting and sublimation degradation. We will present maps of susceptibility to thermal cracking for airless planetary surfaces in our solar system at the meeting and compare to what is known about the regolith. References: Moore et al. (1999) Icarus 140, p. 294-312; Vance et al. (2007) Astrobiology 7, p. 987-1005.

Affiliated with

Also associated with

No associations

Rating

Thermal Weathering on Airless Planetary Surfaces does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Thermal Weathering on Airless Planetary Surfaces, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Thermal Weathering on Airless Planetary Surfaces will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-1769863