Potential Identification of Downslope Mass Movements on Mercury Driven by Volatile-Loss

Home , Berkel (crater), Nabokov (crater)

50th Lunar and Planetary Science Conference 2019 (LPI Contrib. No. 2132) 1804.pdf

POTENTIAL IDENTIFICATION OF DOWNSLOPE MASS MOVEMENTS ON MERCURY DRIVEN BY VOLATILE-LOSS. C.C. Malliband1, S.J. Conway2, D.A. Rothery1, and M.R. Balme1, 1School of Physical Scienc- es, The Open University, Milton Keynes, MK7 6AA, UK ([email protected]), 2CNRS, Laboratoire de Planétologie et Géodynamique, Université de Nantes, France

Introduction: Mass movement has been recog- of hollows on the NE crater rim. The slope features nised on many Solar System bodies. Evidence of mass start just below the crater rim, in a bright stratigraphic movement on Mercury has previously been limited to a layer (Fig. 2). This may be similar to the hollow- single documented example, found in the pyroclastic forming layer in the Nathair Facula vent. vent NE of Rachmaninoff crater (inside Nathair Facu- Possible slope features in Berkel crater. We have la). Here we describe further examples. identified a third possible set of downslope-oriented Currently Identified Examples: We have identi- high albedo slope features in Berkel crater (Fig. 3). fied a number of examples of downslope mass move- This is a complex crater and the features of interest are ment both as serendipitous discoveries during our on- going mapping of the Derain quadrangle [H-10], and during a systematic survey of all MESSENGER narrow A angle camera (NAC) imagery with resolution <20mpp in the adjacent Hokusai quadrangle. Mass movement in Nathair Facula Vent Attention was drawn to the slope features in the Nathair Facula vent on the MESSENGER web-site, but we are aware of no formal study. The features are downslope erosion-deposition systems with an alcove at the head, a chute and a fan at the base. Feature heads appear to develop in a stratigraphic layer of brighter material (Fig. 1). This brighter material is spatially related to hollows [1]. Other imagery of the vent show high albedo slope features in other parts of the vent too. Slope features in unnamed crater (≈285 km N of Nabokov). These newly identified slope features are in a ≈12 km diameter simple impact crater. The crater is surrounded by low reflectance material and has an area B

Fig. 1: The slope features in the vent in Nathair Facu- Fig. 2: Slope features in the unnamed crater (≈285 la. Red dashes indicate location of vent rim and km N of Nabokov). A: Features in high incidence downslope direction. Image resolution: 6.4m/pixel angle image (NAC: EN0252295266M). B: Features (NAC: EN1028933034M) shown in enhanced color. 50th Lunar and Planetary Science Conference 2019 (LPI Contrib. No. 2132) 1804.pdf

Fig. 3: Slope features in Berkel Crater. These features Fig. 4: Slope features on Rustaveli peak ring element. are far more ambiguous than other features presented. The source of these features is not clear. These fea- This is the highest resolution imagery available and tures are unique in the few peak ring elements in so the exact nature of these features is unlikely to be Rustaveli imaged with similar resolution. (NAC: clear until new imagery is obtained by BepiColombo EN1044173928M) (NAC: EN1034838972M) References located on the rim terraces. These features also appear [1] Blewett, D. T., Chabot, N. L., Denevi, B. W., to start in a bright layer below the crater rim. This is Ernst, C. M., Head, J. W., Izenberg, N. R., et al. the least confident identification. (2011). Hollows on Mercury: MESSENGER Evidence Peak ring Element in Rustaveli crater. A possible for Geologically Recent Volatile-Related Activity. Sci- slope feature on a peak ring element in Rustaveli crater ence, 333(6051), 1856–1859. [2] Bart, G. D. (2007). has also been identified.. This is visible only in low Comparison of small Lunar landslides and Martian altitude (<20mpp resolution) imagery (Fig. 4). gullies. Icarus, 187(2), 417–421. [3] Kokelaar B. P., Current work: We have completed a systematic Bahia R. S., Joy K. H., Viroulet S., & Gray J. M. N. T. survey of high resolution NAC imagery in the Hokusai (2017). Granular avalanches on the Moon: quadrangle. We are currently using this to examine Mass‐wasting conditions, processes, and features. slope angles and settings of the features identified in Journal of Geophysical Research: Planets, 122(9), this area. Preliminary work appears to suggest that 1893–1925. [4] Conway, S. J., Balme, M. R., Kreslav- while these slope features are all sited on young, high sky, M. A., Murray, J. B., & Towner, M. C. (2015). angle slopes, there are many more similarly young high The comparison of topographic long profiles of gullies angle slopes that show no such features. This suggests on Earth to gullies on Mars: A signal of water on Mars. that these features must have an additional control on Icarus, 253, 189–204. [5] Brusnikin, E. S., Kreslavsky, their location. We are also comparing the topography M. A., Zubarev, A. E., Patratiy, V. D., Krasilnikov, S. of these features to erosion-deposition systems on the S., Head, J. W., & Karachevtseva, I. P. (2016). Topo- Moon [2, 3], Mars [4,5], and Vesta [6]. Currently our graphic measurements of slope streaks on Mars. Icarus, working hypothesis is that these downslope movements 278, 52–61. [6] Scully, J. E. C., Russell, C. T., Yin, are triggered by sublimation or some other process of A., Jaumann, R., Carey, E., Castillo-Rogez, J., et al. volatile-loss. (2015). Geomorphological evidence for transient water Acknowledgements: CCM acknowledges project flow on Vesta. Earth and Planetary Science Letters, funding from the STFC and Open University Space 411, 151–163. Strategic Research Area. SJC is supported by the French Space Agency CNES, in preparation for BepiColombo.