Lunar and Planetary Science XLVIII (2017) 1302.pdf

SHORELINE FEATURES AT THE DRAINED SYLVENSTEIN LAKE, , WITH APPLICATION TO MARS. J. W. Nußbaumer1 1Johannes Gutenberg University, Mainz, Germany.

Introduction: I investigate the surface morphology Additionally, the reservoir provides flood control for of a study area in upper , Germany, which is the river between Bad Tölz and . characterized by a variety of landforms that may resemble those of martian shoreline landscapes (Fig. 2- 5). The Mars ocean hypothesis states that nearly a third of the surface of Mars was covered by an ocean of liquid water early in the planet’s geologic history[1][2]. This primordial ocean, dubbed Paleo-Ocean and Oceanus Borealis [3], would have filled the Vastitas Borealis basin in the northern hemisphere, a region which lies 4–5 km (2.5–3 miles) below the mean planetary elevation, at a time period of approximately 4.1–3.8 billion years ago. Evidence for this ocean includes geographic features resembling ancient shorelines, and the chemical properties of the Martian soil and atmosphere [4]. Early Mars would have required a denser atmosphere and warmer climate to allow liquid water to remain at the surface. The hypothesis of an ancient (Hesperian) ocean within the northern plains of Mars is one of the most debated issues of the martian geology (e.g., [5] [6] [7] [8] [9] [10]). Such a reservoir in Vastitas Borealis could potentially represent a remnant of a more extensive standing body of water (an ocean) that possibly existed within the northern plains of Mars (e.g., [11] [12]). For how long this body of water was in the liquid form is still unknown. New evidence for a vast northern ocean was published in May 2016. A large team of scientists described how some of the surface in Ismenius Lacus Fig. 1: Image of the Sylvenstein lake quadrangle was altered by two Tsunamis. The Tsunamis were caused by asteroids striking the ocean. Both were thought to have been strong enough to create 30 Km diameter craters. The first Tsunami picked up and carried boulders the size of cars or small houses. The backwash from the wave formed channels by rearranging the boulders. The Sylvenstein lake: Sylvenstein Dam (Fig. 1) is an earthen embankment dam in the Isar valley, in the alpine part of , Germany which impounds the Sylvenstein Reservoir (German: Sylvensteinspeicher). Several hydropower plants were built in the tributary of the upper Isar river in the 1920s, for example at the Achensee and Lake Walchen Power Plant. Therefore, the river ran nearly dry during the dry season. This mainly affected the town of Bad Fig. 2: Image of a shoreline at Sylvenstein lake Tölz. A reservoir was established to ensure a minimum level of water in the river. During the dry season a volumetric flow of 4 cubic metres per second is released to prevent the Isar from running dry. Lunar and Planetary Science XLVIII (2017) 1302.pdf

References: [1] Cabrol, N. and E. Grin (eds.). 2010. Lakes on Mars. Elsevier. NY. [2] Rodriguez, A. et al. (2015) Nature. [3] Baker, V.et al. (1991) Nature, 352, 589-594. [4] Villanueva, G. et al. (2015) Science. [5] Parker, T. et al. (1989) Icarus 82, 111–145. [6] Parker, T.et al. (1993) JGR 98, 11061–11078. [7] Clifford, S.M., Parker, T.J., (2001) Icarus 154, 40–79. [8] Carr, M.H., Head, J.W. (2003). JGR 108, 5042. [9] Tanaka, K. et al. (2003) JGR 108, 8043. [10] Tanaka, K.et al. (2005) Geologic map of the Northern Plains of Mars. USGS Map. p. 2888. [11] Baker, V. et al. 1991. Nature 352, 589–594. [12] Boyce, J. et al. (2005). JGR..11003008B

Fig. 3: Image of a shoreline at Sylvenstein lake

Fig. 4: Image of a shoreline at Sylvenstein lake

Fig. 5: Image of a ripple features at Sylvenstein lake