Classification of Craters Clusters in the Expanded Catalog of Fresh Impact Sites on Mars

Recently, fresh impacts of meter-scaled cosmic objects were discovered on Mars. About half of the projectiles, which formed these impact sites, are destroyed in rarefied atmosphere of Mars and form crater clusters, unfragmented meteoroids result in single craters. Atmospheric density near the Martian surface correspond to about 30 km altitude in the terrestrial atmosphere, thus the study of clusters provides a unique opportunity to estimate meteoroid parameters independently, to investigate various fragmentation types for objects of different composition and origin. This paper considers a processed part of an expanded catalog of impact sites. Data about craters and clusters provide an opportunity to estimate the exponent in the differential and cumulative incremental size-frequency distribution of projectiles as 2.7 and 2.2. Fragmented and not fragmented meteoroids are described by the same distribution. It was suggested to classify clusters into 3 types; the first one refers to one major crater supplemented by some much smaller ones; densely populated clusters (with more than 20 craters) correspond to the second type and the final group relates to sparsely populated clusters (less than 20 craters), which have 2 or more comparable largest craters. The various proposed groups may correspond to different fragmentation scenarios and/or meteoroid properties.