Lunar and Planetary Science XXXV (2004) 1736.pdf

MORPHOMETRIC LIDAR ANALYSIS OF AMBOY CRATER, CALIFORNIA: APPLICATION TO MOLA ANALYSIS OF ANALOG FEATURES ON MARS. D. C. Finnegan1, R. R. Ghent2, J. M. Byrnes3 and M. Bourke4, 1Cold Regions Research & Engineering Laboratory, Hanover NH 03755 [email protected], 2Smithsonian Institution, Washington D.C. 20560-0315 [email protected], 3Department of Geology and Planetary Science, University of Pittsburgh, Pittsburgh, PA 15260-3332, [email protected] 4Planetary Science Institute, Tucson, Arizona 85719-2395, [email protected].

Introduction: Terrestrial analogs are of great Mountains to the southwest and the Bristol importance to our understanding of process Mountains to the northeast. The flow field marks the geomorphology on Mars. The quantitative southeast extent of a Pliocene-Pleistocene northwest- description of forms (geomorphometry) is an trending belt of alkali-basalt volcanics that extends important tool for understanding the evolution of through Pisgah Crater and to Black Mountain analogous landscapes. It demonstrates how aspects of (northwest of Barstow) [9]. the land surface are interrelated and, importantly, The Amboy crater flow field covers about 70 km2 provides parameters that can be related to specific and is primarily characterized by hummocky, geologic processes. This is particularly valuable in vesicular pahoehoe, displaying surface relief of 2-5 planetary geology, where geomorphometry may be m. Surface irregularities have been attributed to both the only means by which these processes can be inflation (tumuli) and deflation (collapse) processes, estimated. Specific geomorphometric techniques though lava tubes have not been identified within the have already been employed in studies on Mars [e.g., flow field [12, 13]. Lava flows emanate from the 1-6]. However, caution must be exercised as issues of vent at Amboy Crater, having been most recently landscape scale and data resolution can be crucial to active 74–85 ka [10, 11]. Other vents within the flow interpretation. Terrestrial analogs can be effectively field are difficult to identify due to the irregular used to test the limitations that MOLA-resolution nature of the flow surface and the partial cover of data impose when modeling geomorphometric sand; however, a probable vent is located ~3 km parameters of landforms on Mars. southeast of Amboy Crater and additional vents have We have recently acquired a high-resolution been proposed to account for local lava drainback LIDAR data set collected over a range of geomorphic features [13]. The sand, where present, varies in environments applicable to Mars. These include thickness from a few centimeters to >1 m. A large, volcanic edifices, fluvial channels and outwash distinctive wind streak extends from Amboy Crater plains, playas, and aeolian deposits (including sand toward the southeast. dunes and wind streaks). We intend to undertake a Amboy Crater proper is ~75 m-high and 460 m- geomorphometric analysis of the LIDAR data using wide. It is a complex cinder cone located in the established approaches that require measurement of northeast portion of the flow field [13] and five fundamental attributes [7, 8]: elevation, slope, constructed of at least four nested and nearly coaxial aspect, profile and plan convexity. This analysis will cinder cones formed during at least six eruptive be followed by an examination of the statistical periods [12]. The eruptive history, though short in properties of the landforms represented in the dataset. total duration records both explosive and effusive Our general aim is to identify optimal LIDAR activity punctuated by quiescent periods and gully parameters for the geological analysis of terrain and formation on the cone flanks. to derive discrete geomorphic signatures of different LIDAR Data: NASA’s Airborne Topographic landscape settings. This paper presents an Mapper LIDAR instrument (ATM-III) is an aircraft- introduction to our data and one of our study sites based scanning laser altimeter flown on NASA’s P3b Amboy Crater, a cinder cone in Southern California. or a twin-engine light aircraft based from NASA’s Study Area: The Amboy Crater volcanic flow Wallops Flight Facility in Virginia. The ATM-III field resides in the Mojave Desert, an internally sensor operates at 2,000 to 10,000 pulses per second drained, landlocked area dominated by broad alluvial at a frequency-doubled wavelength of 532 nm in the deposits and bounded by the San Andreas and blue-green spectral region. For each laser pulse Garlock faults and the southeastern extension of the emitted, a returned spatial vector from the platform to Death Valley fault zone [9]. The flow field erupted the point of reflection is established, providing an onto a flat alluvial plain and divided it into two extremely precise XYZ coordinate of the laser playas, Bristol Dry Lake to the east and Bagdad Dry footprint. Using a conical scanning mirror rotated at Lake to the west. The basin (part of the Basin and 10-20 Hz at an off-nadir angle of 10o, the beam of the Range province) is bounded by the Bullion ATM is directed along an elliptical scanning pattern Lunar and Planetary Science XXXV (2004) 1736.pdf

beneath the aircraft. Swath widths directly of Pavonis Mons [16, 17]). Others, e.g. in Ulysses correspond to flight altitude and rotation rates of the Patera [15] are larger and more numerous. None of scanning mirror and are normally on the order of 500 these features are well imaged using MOLA, even m. with repeat data acquisition, because of the 300 m The Amboy Crater survey in late September 2003 shot spacing of those data. Accurately mapping the utilized a Twin Otter International twin-engine light distribution of cinder cones on Mars is important for aircraft equipped with the ATM-III instrument, a understanding the planet’s geologic evolution. In laser Ring-Gyro Inertial Navigation Unit (INU) and addition to the insights into magmatic and volcanic two survey grade GPS receivers flown at an altitude processes on Mars, the style of ejection and of ~1500 m. Aircraft position was determined by fragmentation can be related to volatile abundance combining the aircraft GPS data with signals and atmospheric pressure throughout the portion of collected concurrently at a nearby base station using Martian history during which these features formed. differential kinematic GPS techniques [14]. The INU An understanding of Amboy-scale features on Earth is used to provide the aircraft pitch, roll and heading will provide a framework within which to examine which are embedded in the ATM telemetry. By similar-scale features on Mars as global 10m integrating individual measurements from the laser resolution data from the Mars Express HRSC become altimeter and kinematic GPS receivers, the ATM available. achieves measurements of surface topography to ~5 References: [1] Aharonson, O., Zuber, M.T., cm. Additional reflectance data collected Rothman, D.H., Schorghofer, N., and Whipple, K.X., simultaneously may also provide independent 2002, Proc. Nat. Acad. Sci. 99, 1780-1783, estimates of relative surface roughness or doi:10.1073/pnas.261704198. [2] Williams, R.M.E. topographic characteristics associated with and Phillips, R.J., 2001, J. Geophys. Res. 106, weathering. The data collected for the Amboy Crater 23,737-23,751. [3] Luo, W, 2002, J. Geophys. Res. site comprises ~300 k data points derived from 15 107, doi:10.1029/2001JE001500. [4] Stepinski T.F., passes over the site with a horizontal shot spacing of Marinova, M.M., McGovern, P.J., and Clifford, S.M., ~25-50 cm. 2002, Geophys. Res. Lett. 29, Application to Mars: The current study will doi:10.1029/2002GL014666. [5] Orosei, R., Bianchi, provide insight into how higher resolution R., Coradini, A., Espinasse, S., Federico, C., topographic data may increase our understanding of Ferriccioni, A., and Gavrishin, A.I., 2003, J. the nature of geomorphic features and associated Geophys. Res. 108, doi:10.1029/2002JE001883. [6] geologic processes on Mars in three ways. 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