Morphologic and Slope Studies of Crater Gullies in the High-Northern Latitudes of Mars.

Abstract:

Gullies on Mars are usually defined by a source alcove and a channel that shallows into a debris apron. This holds true for many gullies. However, several gullies in the northern high-latitudes (>50° N) show complex forms. This study expands on previous analysis (Huang et al. 2020, LPSC) of northern high-latitude sites. Morphometric and morphologic comparison of these gully systems can provide insight to gully forming processes and past martian northern environments.

Crater 1 (63.8°N) has numerous poorly developed gullies on its E and W interior slopes. One exceptional gully displays a braided morphology in which channels incise the entire apron. This morphology may be due to unconsolidated sediment composing the crater slopes. At the deepest part of its alcove is an intriguing, elongated 12-m high mound eroded along its downslope trend. We interpret this to be a dust-covered snowpack.

Crater 2 (53.6°N) is located on Lyot Crater’s northern ejecta blanket. While all its slopes contain gullies, only two have distinct aprons. The first has several indistinct channel-like forms on its apron. Its alcove has escarpments suggesting episodic flow. The latter consists of several gullies merged into a lobate apron. Pitted features on the apron’s surface, consistent with sublimation processes, suggest high-volatile subsurface volumes.

A new site, Crater 3 (60.197° N), has a micro-environment likely due to insolation. Its NW slope is devoid of gullies, but lobate features suggest frost creep. All other slopes show gullies with somewhat deeply incised channels that form laterally extensive tributary systems. Most gullies in this crater have poor aprons, but several bright aprons on the N and E slopes exist. Gully alcoves form in the crenulated crater rim.

We have mapped these gully systems anddelineated their drainage basin areas. Preliminary results show that the Crater 1 gully has an alcove slope ~16° and apex slope ~11°, while the two Crater 2 gullies studied have higher alcove (~30° and 27°) and apex slopes (20° and 20°). Crater 1 and Crater 2 are below the repose and apex angles required for dry flow deposition (~32° , >21°; Kolb et al. 2010, Icarus). Further analysis of detailed morphologies, slopes, and morphometrics is being conducted.

Funding provided by: 2019 SETI REU (RH), 2020 NASA ARC Summer internship (RH, NG), MRO HiRISE (VG)