Crater Relaxation and Stereo Imaging of the Icy Satellites of Jupiter and Saturn

Details Crater Relaxation and Stereo Imaging of the Icy Satellites of Jupiter and Saturn Crater Relaxation and Stereo Imaging of the Icy Satellites of Jupiter and Saturn

Dec 2010

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010agufm.p21b1596p&link_type=abstract

American Geophysical Union, Fall Meeting 2010, abstract #P21B-1596

Other

[5420] Planetary Sciences: Solid Surface Planets / Impact Phenomena, Cratering, [5455] Planetary Sciences: Solid Surface Planets / Origin And Evolution, [6218] Planetary Sciences: Solar System Objects / Jovian Satellites, [6280] Planetary Sciences: Solar System Objects / Saturnian Satellites

Scientific paper

Crater relaxation has been used as a probe of subsurface temperature structure for over thirty years, both on terrestrial bodies and icy satellites. We are developing and testing two independent methods for processing stereo pairs to produce digital elevation models, to address how crater relaxation depends on crater diameter, geographic location, and stratigraphic position on the icy satellites of Jupiter and Saturn. Our topographic profiles will then serve as input into two numerical models, one viscous and one viscoelastic, to allow us to probe the subsurface thermal profiles and relaxation histories of these satellites. We are constructing stereo topography from Galileo and Cassini image pairs using the NASA Ames Stereo Pipeline (Moratto et al. 2010), an automated stereogrammetry tool designed for processing planetary imagery captured from orbiting and landed robotic explorers on other planets. We will also be using the commercial program SOCET SET from BAE Systems (Miller and Walker 1993; 1995). Qualitatively, it is clear that there are large spatial variations in the degree of crater relaxation among Jupiter’s and Saturn’s satellites. However, our use of stereo topography will allow quantitative measures of crater relaxation (e.g. depth:diameter ratio or equivalent) to be derived. Such measures are essential to derive quantitative estimates of the heat fluxes responsible for this relaxation. Estimating how surface heat flux has varied with time provides critical constraints on satellite thermal (and orbital) evolution. Craters undergo viscous relaxation over time at a rate that depends on the temperature gradient and crater scale. We are investigating how the near-surface satellite heat flux varied in time and space, based on our crater relaxation observations. Once we have crater profiles from our DEMs, we use them as input to two theoretical approaches: a relatively simple (viscous) numerical model in which time-varying heat fluxes can be included, and a more sophisticated (viscoelastic) one in which the temperature structure is fixed. The first follows the formulation of Grimm and Solomon (1988), and is a relatively simple Newtonian viscous relaxation model, in which the temperature and viscosity fields can evolve with time. The second is a more complicated spherical viscoelastic model, in which the temperature field is fixed (Zhong et al. 2003). The viscous model is suitable for rapid exploration of parameter space, while the viscoelastic will be used for more detailed investigation of selected parameter combinations. References: Grimm, R.E., and S.C. Solomon, J. Geophys. Res. 93, 11911-11929, 1988. Miller, S.B., and Walker, A.S., 1993. ACSM/ASPRS Annual Conv. 3, 256-263. Miller, S.B., and Walker, A.S., 1995. Z. Phot. Fern. 63(1), 4-16. Moratto, Z. M., et al., LPSC 41, abstract #2364, 2010. Zhong, S.J., et al., 2003. G.J.Int. 155, 679-695. Acknowledgments: This work is funded by NASA’s Outer Planets Research program.

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