HR: 1340h
AN: P23A-0177    [Abstracts]
TI: Tyrrhena Patera, Mars: Insights Into Volcanic and Erosional History From High-Resolution Images and Impact Crater Populations
AU: * Berman, D C
EM: bermandc@psi.edu
AF: Planetary Science Institute, 1700 E. Ft. Lowell Rd. Suite 106, Tucson, AZ 85719 United States
AU: Crown, D A
EM: crown@psi.edu
AF: Planetary Science Institute, 1700 E. Ft. Lowell Rd. Suite 106, Tucson, AZ 85719 United States
AU: Hartmann, W K
EM: hartmann@psi.edu
AF: Planetary Science Institute, 1700 E. Ft. Lowell Rd. Suite 106, Tucson, AZ 85719 United States
AB: Analyses of surface morphology revealed in high-resolution images coupled with size-frequency distributions of impact craters are being used to assess the volcanic and erosional history of Tyrrhena Patera, a Martian highland volcano located northeast of the Hellas Basin within Hesperia Planum. Tyrrhena Patera exhibits a complex summit caldera region, highly eroded flank materials extending for 100s of km, and a lava flow field that extends for over 1000 km to the southwest along the regional slope toward Hellas Planitia. The low, broad shape of the volcano and its erosional morphology were attributed in previous studies to explosive eruptions, perhaps due to interactions with ground water/ice, followed by dissection of the resulting sequence of pyroclastic deposits by a combination of groundwater sapping and surface runoff. Mars Odyssey THEMIS and Mars Global Surveyor MOC images allow detailed studies of the following surfaces at Tyrrhena Patera: a) summit/caldera region, b) high-standing remnants of eroded flank materials, c) floors of erosional valleys within flank materials, d) SW lava flow field, and e) floor of volcanic rille connecting caldera to flow field. Preliminary results show that age constraints for eroded flank materials from craters with diameters between ~250 m and ~1 km (counted on THEMIS images) are consistent with Viking results (i.e., Late Noachian/Early Hesperian explosive volcanism with effusive eruptions in Late Hesperian/Early Amazonian). Crater counts from MOC images also show ancient surfaces on Tyrrhena Patera's flanks, but greater variability due to local preservation and modification effects. Within the eroded flanks, valley floor surfaces exhibit fewer craters than adjacent uplands, as well as a gradual decrease in fresh craters relative to production function "isochron" shapes as diameter decreases, suggesting progressive degradation of an ancient surface rather than widespread resurfacing. The crater population on the floor of Tyrrhena Patera's volcanic rille shows a younger surface age than for flank materials at crater diameters below 500 m. Crater counts from THEMIS images for the summit region indicate slightly younger surfaces than the surrounding flanks, which can be attributed to pyroclastic deposits and/or enhanced aeolian activity.
DE: 5480 Volcanism (6063, 8148, 8450)
DE: 6022 Impact phenomena (5420, 8136)
DE: 6225 Mars
DE: 8148 Planetary volcanism (5480, 8450)
DE: 8404 Volcanoclastic deposits
SC: Planetary Sciences [P]
MN: Fall Meeting 2005