37th DPS Meeting, 4-9 September 2005
Session 32 Mars' Surface
Poster, Tuesday, September 6, 2005, 6:00-7:15pm, Music Recital Room

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[32.25] The Martian Crater Size-Frequency Distribution and the Evolutionary History of Mars

S. C. Werner (Freie Universitaet Berlin), B. A. Ivanov (RAS - Institute for Dynamics of Geospheres, Moscow), G. Neukum (Freie Universitaet Berlin)

In order to gain an understanding of the geologic evolution of a terrestrial planet it is vital to place the different geological processes involved in shaping the planetary surface into chronological order. Global stratigraphic schemes for planetary bodies are usually based on the impacts of planetesimals that remain as craters or crater-related features on planetary surfaces. The cratering record shows the bombardment integrated through the morphologically recorded geological lifetime of a certain body. The record also reveals the geological history of a specific surface unit due to spacial variations of the crater frequencies and temporal variations of the crater-forming projectile flux. Prerequisite to the interpretation of crater size-frequency data for various geologic units of different ages is the determination of the shape of the crater-production function, implying the primary source of projectiles which impacted the planetary surface, and the application of a cratering-chronology model. The lunar production function is the best investigated among terrestrial planet surfaces, as based on a large image data base at all resolutions and is described as a polynomial function of 11th degree (Neukum, 1983, Neukum and Ivanov, 1994). Since the same projectile population (bodies derived from the asteroid belt, Ivanov et al., 2001) impacted all inner solar system bodies, the lunar production function can be scaled to impact conditions on these bodies, taking into account parameters such as impact velocity and angle of the projectile, surface gravity, atmospheric effects, and density and rheologic properties of the target surfaces. The latest Martian production--function polynomial has been constructed from the refined lunar production function, based on an estimation of crater scaling parameters (Ivanov, 2001). Here we present the first measured Martian Crater Size-Frequency Distribution over the whole diameter-size range, based on Viking, HRSC, THEMIS and MOC data. Aspects of secondary cratering, resurfacing and exhumation and their influence on the cratering record will be highlighted and insights to the evolutionary history of Mars will be given. The authors acknowledge the funding of the Deutsche Forschungsgemeinschaft (DFG).

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Bulletin of the American Astronomical Society, 37 #3
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