Ice flow in the deepest part of Mars: the banded terrain in Hellas
basin
Supervisors: Pr. F. Schlunegger and Pr. N. Thomas
Co-supervisors: M. R. El-Maary and K. P. Norton
The Hellas basin, located in the southern hemisphere (centered at 40.8°S, 67.8°E), is one of
the oldest (~3.95 Ga) and one of the largest basin of Mars. The interior of the basin displays a
relative smooth due to the deposition of several units: Alpheus Colles plateau, smooth plain
terrains, reticulate and honeycomb terrains, and banded terrain (Fig. 1). The banded terrain
covers a large band (35–42°S, 51–60°E) of the NW of the basin. This latest unit is composed
of smooth-looking bands that display signs of viscous flow (Fig. 1) and a paucity of
superimposed impact craters indicative of an Amazonian age. The morphology of the bands
varies from linear to concentric form (Diot et al., 2014). Contacts and cross-cutting
relationships between the different units suggest a major period of deposition in the NW
Hellas between the Late Noachian and the Early Amazonian. No significant deposits seem to
cover the banded terrain. While it appears clear that the bands have eroded the Alpheus
Colles plateau, the contact between the banded terrain and the honeycomb situated to the
north is complex and seems to be a northward progressive transition. Some honeycomb cells
display internal banded deposits sharing close similarities with the banded terrain, which may
indicate that the banded terrain may have covered a larger area of the NW interior of Hellas
in the past (Diot et al., submitted to Icarus). Detailed observations carried out using very
high-resolution datasets (HiRISE) revealed the presence of multiple landforms in the banded
terrain interpreted to be periglacial landforms (Diot et al., in preparation). Such landforms
constitute geomorphologic evidences of the degradation of a permafrost through diverse
processes like thermal contraction cracking and sublimation of ice in the subsurface. The
mapping of these landforms showed that they are laterally distributed in the banded terrain,
thus indicating the presence of ground ice in the entire banded terrain. Topography and
multiple interactions between neighboring bands seem to be key parameters for the shaping
of the bands. Multiple changes in directions of bands are also linked to the interaction with
the surrounding bands. Further, in lots of areas, the bands are laterally constrained by the
occurrence of other bands. Thereby, the multiple bands observed in the banded terrain appear
to evolve together as one complex system.
Figure 1. 3 dimentional view from a DTM showing the complex spatial organization of the
banded terrain in the NW Hellas basin on Mars.
List of publications:
Diot et al., 2014 in Planetary and Space Science. The geomorphology and morphometry of
the banded terrain in Hellas basin, Mars. doi:10.1016/j.pss.2014.06.013
Diot et al., 2015, submitted to Icarus. The stratigraphy of the interior of the Hellas basin,
Mars.