A probable ancient nearshore zone in southern Utopia on Mars unveiled from observations at the Zhurong landing area

Abstract

The Chinese Mars rover Zhurong successfully landed in southern Utopia Planitia on Mars in May 2021. Previous research suggested a Hesperian ocean may have existed in the northern lowland on Mars. Recent research observed water-related features at the Zhurong landing site from in situ data. In this study, we conducted a comprehensive geomorphological analysis of the landing area using remote sensing data, supplemented by in situ observations, and unveiled features consistent with the existence of a nearshore zone in southern Utopia. Different types of water-related geomorphological features were separated by specific topographic contours, suggesting different types of marine environments. The area was subdivided into a foreshore highland-lowland transition unit, a shallow marine unit and a deep marine unit. In situ observations including sedimentary deposit rocks, water-related lamination features, and subsurface sedimentary layers, also indicate past water activities. Results suggested an evolution scenario of the nearshore zone in southern Utopia: (1) Flooding of the Utopia Planitia in Late Noachian around 3.65-3.68 Ga reached the foreshore unit; (2) formation of the shallow and deep marine units after the flooding was completed by about 3.5 Ga and 3.42 Ga in Early Hesperian, respectively; (3) gradual loss of subsurface volatiles during the Amazonian epoch.