A Creeping Soil Field on Mars

Introduction: A creeping soil field exists on Mars. It is not distinctly laid out, no erosion is visible and its channel is either not clearly defined or possibly does not exist. The movement of the soil field on slightly inclined slope is very slow (in terms of martian time measures), interrupted by periods of standstill. The character of the movement is phenomenologically close to the creep of terrestrial glaciers or to slow movements of terrestrial soil fields. Observation: The particular field dealt with is shown in Fig. 1, adjusted from [1]. Long, narrow, and relatively bright tapered stripes, resembling hair strands, are observed in the picture; the strands start at rock outcrops protruding from the soil field and get gradually tapered when following the slope down, being slightly curved in correspondence with the slope lines. In the description that accompanies the original picture, the strands have been explained as traces of wind streaks (see [1]). This, however, does not correspond to the nature of gas flows, which, contrary to the strands mentioned, would spread the dust or other volatiles in veil-wise form. The result of such wind streaking and the ensuing dust settlement can be seen on other MOC/MGS images (e.g., [2], Fig. 2). However, the tapered strands can be easily explained by movement of soil along the outcrops, where the bright rock gets abraded, and the abraded material is carried away down the slope. Further, two important forms can be observed on the surface of the soil field: – pitch-change lines indicating convexity of the slope surface (Fig. 1, white arrows), – fissures indicating concave surface (Fig. 1, two of the fissured areas are highlighted by black arrows). Both these phenomena are commonly encountered on terrestrial sand fields. Conclusion: The soil field discussed, displayed in Fig. 1, shows signs of creeping movement of the soil. Though the Author did not identify similar landforms on Mars, other soil fields of this kind are likely to exist there.