Dark halos produced by current impact cratering on Mars

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Hundreds of new impact craters have been observed to form on Mars since spacecraft began imaging that planet. New impact craters produced visible ejecta deposits and many of them also have visible rays, similar to lunar and mercurian craters. However, some of the new martian impact craters have a circular feature of relatively low reflectance that we call a “halo.” This feature is distinct from the usual visible ejecta deposits or ray patterns. In this paper we present an observational study of this halo feature and we discuss the results of this study with respect to the nature of the halos: what they are and how they may have formed. To address these questions, we measured diameters of both halos and their central craters. We found a strong correlation between halo diameter and crater diameter, which indicates that the nature of the halos is fundamentally governed by the amount of impact energy available at their formation. Specifically, halo size is controlled by impact energy according to the non-linear relationship DH ∝ E2/3, where DH is the diameter of the halo and E is the impact energy. We also found that certain factors may influence the formation of the halos: a thicker dust layer and lower elevations are both correlated with larger halos. From these correlations we conclude that the local surface characteristics as well as local atmospheric pressure influence the formation of the halos. Our description and analysis of the martian halo features provide a framework upon which specific halo formation mechanisms can be developed and tested in the future.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Dark halos produced by current impact cratering on Mars
Series title Icarus
DOI 10.1016/j.icarus.2019.03.004
Volume 328
Year Published 2019
Language English
Publisher Elsevier
Contributing office(s) Astrogeology Science Center
Description 13 p.
First page 45
Last page 57
Other Geospatial Mars
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