Open AccessCombinations of processes responsible for Martian impact crater “layered ejecta structures” emplacement
Author(s) -
Komatsu Goro,
Ori Gian Gabriele,
Di Lorenzo Stefano,
Rossi Angelo Pio,
Neukum Gerhard
Publication year - 2007
Publication title -
journal of geophysical research: planets
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2006je002787
Subject(s) - ejecta , impact crater , geology , martian , hypervelocity , astrobiology , geophysics , petrology , mars exploration program , geomorphology , physics , astronomy , supernova
We utilized images and stereo‐derived topographic data acquired by the High Resolution Stereo Camera (HRSC) and Thermal Emission Imaging System (THEMIS) images together with other data in order to study the geology of “layered ejecta structures” associated with relatively pristine Martian impact craters. The geomorphology and morphometric properties indicate their origin as complex combinations of a variety of impact processes. The studied (inner) layered ejecta structures often exhibit ground‐hugging characteristics, and many of them do not have topographic profiles expected from simple ballistic emplacement. Such profiles include ones that are plateau‐shaped or thickening outward. We think that water‐rich fluidized flows driven by the momentum due to the impact and by gravity, together with ballistic emplacement and vortex produced by the atmosphere‐ejecta curtain interaction, were essential to the (inner) layered ejecta structure formation. We hypothesize that the thinner outer layered ejecta structures were formed by various combinations of shockwave‐induced liquefaction of water‐rich near‐surface sediments, ballistic emplacement of ejecta‐entraining water, and strong winds (expanding vapor, vortex, base surge) related to the impact. The contribution of each proposed layered ejecta structure formation mechanism should have been variable depending on the condition of the impact.