Active Boulder Movement at High Martian Latitudes

Abstract

Lobate stony landforms occur on steep slopes at high latitudes on Mars. We demonstrate active boulder movement at seven such sites. Submeter-scale boulders frequently move distances of a few meters. The movement is concentrated in the vicinity of the lobate landforms but also occurs on other slopes. This provides evidence for a newly discovered, common style of activity on Mars, which may play an important role in slope degradation. It also opens the possibility that the lobate features are currently forming in the absence of significant volumes of liquid water.

Keywords: Boulders; Ice; Mars; Mass wasting; Periglacial processes; Surface activity.

Figure 1

Overview of Site 1. (a) Lobate features are concentrated on the north‐facing wall. A bright deposit is associated with a gully at upper right. (b) Enlargement showing lobate features in more detail. Box shows the location of Figures 2a and 2b. The regular texture between many of the boulder lobes could be aeolian bedforms or due to ground ice processes. (HiRISE image ESP_026564_2405).

Figure 2

Examples of boulder changes. (a, b) A boulder detach from a lobate structure and advance several meters. (c, d) A boulder rotate down slope (upper right arrow) and additional shadows that disappear (lower left arrows). Possible corresponding boulders appear downslope. (HiRISE images ESP_026564_2405 [a], ESP_035346_2405 [b and c], and ESP_042889_2405 [d]. See the supporting information for blink comparisons).

Figure 3

Locations of boulder shifts at Sites 1 and 7. Shifts are concentrated near the lobate features. (HiRISE images ESP_035346_2405 [a] and ESP_053669_2395 [b]). Note that movement only occurs on the crater walls, not on the shallowly sloping floor.

Figure 4

Rockfalls in a crater in Meridiani Planum. Tracks and bounce marks in (b) show the paths of individual fragments. Arrow indicates one fragment that is resolved by HiRISE. (HiRISE images ESP_039760_1775 [a] and ESP_040327_1775 [b]).