Assessment of Antipodal-Impact Terrains on Mars

✍ Scribed by David A. Williams; Ronald Greeley

• Publisher: Elsevier Science
• Year: 1994
• Tongue: English
• Weight: 524 KB
• Volume: 110
• Category: Article
• ISSN: 0019-1035
• DOI: 10.1006/icar.1994.1116

✦ Synopsis

The regions antipodal to Mars' three largest impact basins, Hellas, Isidis, and Argyre, were assessed for evidence of impactinduced disrupted terrains. Photogeology and computer modeling using the Simplified Arbitrary Lagrangian Eulerian (SALE) finite element code suggest that such terrains could have been formed by the Hellas impact. Maximum antipodal pressures are (1100 \mathrm{MPa}) for Hellas, (520 \mathrm{MPa}) for Isidis, and (150 \mathrm{MPa}) for Argyre. The results suggest that if antipodal fracturing were associated with later volcanism, then Alba Patera may be related to the Hellas event, as proposed by Peterson (Lunar Planet. Sci. 9, 885-886, 1978)). Alba Patera is a unique volcano in the solar system, being a shield volcano which emitted large volume lava flows. This volcanism could be the result of the focusing of seismic energy which created a fractured region that served as a volcanic conduit for the future release of large volumes of magma. No disrupted terrain features are observed antipodal to the Isidis or Argyre basins, although some of the old fractures in Noctis Labyrinthus could have originated in response to the Isidis impact, and later been reactivated by the Tharsis tectonics assumed to have produced Noctis. If the lower calculated antipodal pressures for Argyre were capable of producing disrupted terrains, then the terrains have been covered subsequently by volcanic or aeolian material, or modified beyond recognition. O 1994 Academic Press, Inc.