HR: 1330h
AN: P22A-0058    [PDF]
TI: THEMIS Observations of Domes and Associated Lineaments in Arcadia Planitia
AU: * Milam, K A
EM: kmilam@utk.edu
AF: Planetary Geosciences Institute Department of Earth and Planetary Sciences, University of Tennessee 306 EPSB, Knoxville, TN 37996-1410 United States
AU: McSween, H Y
EM: mcsween@utk.edu
AF: Planetary Geosciences Institute Department of Earth and Planetary Sciences, University of Tennessee 306 EPSB, Knoxville, TN 37996-1410 United States
AB: The northern plains of Mars contain several high concentrations (Acidalia, Utopia, Elysium, etc.) of small ($<$10 km diameter) domes, proposed to be volcanic. Recent data sets from the Mars Global Surveyor and Mars Odyssey spacecraft provide new insight into the formation of domes in Arcadia Planitia. Daytime and nighttime thermal infrared (TIR) data from the Thermal Emission Imaging System (THEMIS), visible images from THEMIS and the Mars Orbiter Camera, and elevation data from the Mars Orbiter Laser Altimeter were used to study a 390,000 km $^{2}$ area $\sim$1500 km to the northwest of Elysium Mons. Of interest is a region centered on Tyndall crater and bordered by Phlegras Montes to the west. The area is characterized by gentle, westward-sloping plains, with noticeable slope breaks along several N-S trending wrinkle ridges. Several hundred circular domes dot this area. Domes display features consistent with a volcanic origin. Most are circular to slightly elliptical at their base, with basal diameters ranging from 0.5-6 km. Summits typically rise $<$300 m above the surrounding plains. Domes have shallow slopes (lacking significant slope breaks) that range from 1-9$\deg$. Visible images and TIR-derived temperature data suggest that slopes are composed of finer-grained material (as compared to the coarser-grained summits). Less than 25% of domes appear to have summit depressions and ~ 1% show fractured summit areas. Some domes appear to be randomly distributed, but many are aligned in chains according to wrinkle ridge orientations. Using THEMIS data, we have detected over 165 domes that are aligned with and superimposed upon over 145 lineaments. Most lineaments are $<$500 m in width and range from 1-66 km in length. Many lineaments do follow N-S trends similar to those of wrinkle ridges, although other orientations are common. Several lineaments can be seen as open fractures, while others appear to be filled with fine-grained sediment. While most domes are superimposed upon lineaments, 3 domes area appear to be cross-cut by lineaments. No laterally extensive flows have been detected as emanating from lineaments, nor have similar lineaments been detected immediately outside the study area. The association of domes and lineaments is consistent with observations of volcanic constructs along open fissures in many terrestrial volcanic fields. Assuming a volcanic origin, the dome-lineament relationship suggests localized, structurally-controlled eruptions along open fissures. Initial extension caused the opening of fractures, which was followed by localized extrusions. Such localized development can provide information about eruption rates, magma compositions, or the physical properties of erupted lava. Either during or after volcanic activity, continued extension led to several domes being dissected by fissures.
DE: 6225 Mars
DE: 8414 Eruption mechanisms
DE: 8450 Planetary volcanism (5480)
SC: Planetary Sciences [P]
MN: 2003 Fall Meeting