Mars as a compelling target in the continuing search for signs of ancient extraterrestrial life

Abstract

The purpose of this white paper is to document the need to continue our search for ancient life on Mars.Upcoming missions are taking the first steps by directly seeking signs of ancient life with in situ exploration (Mars 2020 and ExoMars) and Mars Sample Return (MSR). However, these missions will not explore the full suite of habitable paleoenvironments on Mars and only a limited geographic region. Whereas a positive result would be a watershed moment for humanity and would compel us to explore the full extent of Mars' biosphere, a negative result would not indicate life never existed on Mars, and additional investigations will be needed. So in either case, as we go forward into the next decade, we will need to target a broader range and distribution of habitable paleoenvironments on Mars, constrain the history of water on Mars, and define a more complete catalog of possible biosignatures, as well as their ubiquity and stability under Mars' preservational conditions. This will also require instrumentation developments that could improve the detection of ancient biosignatures during future robotic and human missions.

A predictive model for the ichnological suitability of the Jezero crater, Mars: searching for fossilized traces of life-substrate interactions in the 2020 Rover Mission Landing Site

“…Bioerosion, the mechanical or biochemical drilling of a rigid substrate (Fig. 2C) (Frey & Pemberton, 1985;Bromley, 1996;Pemberton et al, 2001), is rarely mentioned in research related to Mars 2020 (e.g., Czaja et al, 2020;Ivarsson, Sallstedt & Carlsson, 2020). Biostratification, i.e., the process by which organisms impart stratification features to the substrate (Fig.…”

“…According to the Landing Site Data Sheets (NASA, 2020b), microbial-induced sedimentary structures may have been preserved in the quiet deltaic or lacustrine deposits of the Jezero Crater. This lack of attention is surprising because plausible ancient Martian biosignatures are considered to be similar to the types of biosignatures characterizing the Precambrian rock record of Earth (McMahon et al, 2018;Czaja et al, 2020), which is indeed rich in fossilized products of life-substrate interactions (ichnofossils). The Precambrian rock record comprises 1.7 Ga (billion years) microborings (Zhang & Golubic, 1987), 2.1 Ga macroscopic burrows (El Albani et al, 2019), 3.2 Ga MISS (Noffke et al, 2006;Heubeck, 2009;Noffke, 2009) and 3.49 Ga stromatolites (Allwood et al, 2007).…”