Young lava flows on the eastern flank of Ascaraeus Mons: Rheological properties derived from High Resolution Stereo Camera(HRSC) images and Mars Orbiter Laser Altimeter(MOLA) data

Abstract

We report on estimates of the rheological properties of late-stage lava flows on the eastern flank of Ascraeus Mons, Mars. From previous studies it is known that the dimensions of flows reflect rheological properties such as yield strength, effusion rates, and viscosity. Our estimates are based on new high-resolution images obtained by the High Resolution Stereo Camera (HRSC) on board the European Space Agency's Mars Express spacecraft in combination with Mars Orbiter Laser Altimeter (MOLA) data. Compared to earlier studies, the high spatial resolution of the HRSC and MOLA data allowed us to map 25 late-stage lava flows and to measure their dimensions, as well as their morphological characteristics, in greater detail. Our estimates of the yield strengths for these flows range from ∼2.0 × 102 Pa to ∼ 1.3 × 105 Pa, with an average of ∼2.1 × 104 Pa. These values are in good agreement with estimates for terrestrial basaltic lava flows and are comparable to previous estimates derived for a small number of lava flows on Ascraeus Mons. Our investigation indicates that the effusion rates for the studied Ascraeus Mons flows are on average ∼185 m3 3 s-1, ranging from ∼23 m3 s-1 to ∼404 m3 S-1. These results are higher than earlier findings that indicate effusion rates of 18-60 m3 s-1, with an average of 35 m3 s-1. However, our effusion rates are similar to terrestrial effusion rates of Kilauea and Mauna Loa and other Martian volcanoes. On the basis of our estimates of the effision rates and the measured dimensions of the flows, we calculated that the time necessary to emplace the flows is on average ∼26 days. Viscosities were estimated on the basis of yield strengths and effusion rates, yielding average values of ∼4.1 × 106 Pa-s and ranging from ∼1.8 × 104 Pa-s to ∼4.2 × 107 Pa-s. On the basis of newly available data sets (e.g., HRSC, MOLA) we are now able not only to identify possible differences in eruptive behavior between Ascraeus Mons and Elysium Mons but also to study such differences over time. Copyright 2007 by the American Geophysical Union.