Glacial Sculpture on Mars’ Ancient Megacanyons : A Presentation of Project ‘Icefloods’

Mars is a hyperarid, global cryosphere, and likely has been for over 3 Gyr. Contrastingly, during the so-called early Mars period 4-3.5 Gyr go, water flowed within thousands of valleys, in crater lakes, producing ancient deltas, building ice sheets, and possibly ponding in oceans [1]. However, this early benign climate collapsed with the continued loss of Mars’ atmosphere in the Hesperian period, ~3.5-3 Gyr ago.  Activity in most outflow channels has been dated from this period [1-3], with some channels displaying younger [2] and/or later [3] erosive episodes. Within the channels there are landforms indicative of the flow of massive amounts of fluid, including streamlined islands and longitudinal grooves and ridges, often seen diverging around obstacles. Among the outflow channels, Kasei Valles is of particular interest because of its large size, as the volume of water involved in its formation could have contributed substantially to the existence of a northern ocean [2-3] (figure 1c).

 Owing to the similar landforms carved by the Missoula megafloods observed in the Channeled Scablands on Earth [1,4] (figure 2, c and f), Kasei Valles along with other martian outflow channels is analogously interpreted to be the result of ancient massive outburst floods [1-4]. Support for this hypothesis includes the presence and morphology of streamlined islands, the presence of regularly spaced longitudinal ridges, and the presence of hanging valleys and U-shaped valleys [1,4,5]. Debate ensues, however, regarding the near surface stability and availability of liquid water during the Hesperian period required to produce repeated erosion at the scales of observed in Kasei Valles. Alternative hypotheses that could explain outflow channel formation include ice streaming [5-6] or regional construction and local erosion by turbulent lava flows [7].

Figure 1. (a) Global topography of Mars with outflow channel distribution. (b) Timeline of Earth (top) and Mars (bottom) highlighting the origin of life on Earth (green star) and the evolution of Mars’ climate and hydrology through time, and the moment of outflow channel incision coinciding the collapse of the early water-bearing climate. (c) Kasei Valles, the largest outflow channel. (d) Hesperian outflow channels, marking the landing site of ESA’s ExoMars Rosalind Franklin Rover, which will search of evidences of life (red circle on Oxia Planum).

This project aims to explore the contrasting hypothesis that Kasei Valles was eroded by an ice stream [5-7], a region of channelized, fast-flowing ice within an ice sheet, and reinvestigate the origin of other outflow channels under this perspective. Drawing from fluid dynamic simulations, analogue field work, geological mapping, and climate modelling, the objective is to test the ice sculpture hypothesis first raised by Baerbel Lucchitta (1982) [5-6], which if correct, would substantially impact our understanding of Mars’ transitional Hesperian climate, the nature of its hydrological cycle, and the possibility of a Hesperian ocean.

Our preliminary observations and results tentatively support this hypothesis [8]. In terms of geomorphology, we show that bedforms such as grooves and streamlined islands, spatial scales, cross-section geometry, and planform morphology all are consistent with terrestrial ice streams, even more so than with the classical analogue of the Channeled Scablands (figure 2, compare a&d with b&e and c&f). Moreover, Kasei Valles demonstrates a lack of significant landforms associated with turbulent flow, such as kolks, turbulent eddie marks, or labyrinthine terrain, which are well visible and reported for the Channeled Scablands as well as other megaflood-type landscapes [4].

Fig 2. Overview and comparative of Kasei Valles and analogue sites and processes. (a) Kasei Valles (MOLA elevation on hillshade). (b) Graphic outline of the northeast Greenland ice stream. (c) Outline of the Channeled Scablands (US) adapted from the USGS. (d) Longitudinal grooves in Kasei Valles (CTX mosaic). (e) Megascale glacial lineations and megagrooves, Dubawnt Lake ice stream bed (ArcticDEM hillshade). (f) Grooves carved by Missoula megaflood, Channeled Scablands (Maxar, Google Earth, contrast-stretched).

 We use fluid dynamic simulations to analyze, explain, and interpret the scale and bedforms that are observable within and around Kasei Valles, and then consider comparisons with relevant terrestrial analogues beyond the classic Channeled Scablands site as well as geomorphological characteristics of fast-flowing glacial bodies, to draw conclusions regarding the origin of Kasei Valles, and implications for other outflow channels [8]. Finally, we will contextualize its climatic implications during the time of climate collapse (figure 1) at the end of the Hesperian period, following previous work [10].

Acknowledgements. This project has received funding from the European Research Council (ERC) under the European Union’s Horizon Europe research and innovation programme (Grant agreement No. 101165197 - ICEFLOODS).

References: [1] Carr M.H. (2007) C.U.P (Vol.6). [2] Chapman M.G. et al. (2010a) EPSL, 294 (3-4). [3] Chapman M.G., et al. (2010b). [4] Baker, V.R. and Milton, D.J., (1974) Icarus, 23(1), 27-41. [5] Lucchitta B.K. (1982) JGR: Solid Earth 87(B12). [6] Lucchitta B. K. (2001) GRL, 28(3), 403-406. [7] Leverington D.W. (2011) Geomorphology 132(3-4) [8] Grau Galofre et al., 2023, LPSC. [9] Stokes C.R. and Clark, C.D. (2001) Quaternary Sci. Rev. 20(13). [10] Turbet et al., 2017 Icarus 288, 10–36.