1Queensland University of Technology, Brisbane, Australia
Recent orbiter and rover missions to Mars have culminated in a new appreciation of the vastly difference surface conditions that prevailed in Mars’ distant past. During the Noachian (roughly corresponding to the Hadean and early Archean), Mars appears to have supported a much denser atmosphere, abundant standing bodies of liquid water, significant volcanism and a stronger magnetic field. The next few years will see the arrival of several geology-focused, multi-billion-dollar, lander and rover missions supported by the USA, the European Union, and China.
Astrobiologists interested in the possibility of a Martian biosphere are focusing their attention on rocks dating from the Noachian, which, compared to the Earth, appear to be well-preserved and exposed in relatively extensive outcrop. NASA has chosen an extensive package of sedimentary rocks dating from this time period for it’s next flagship mission: the Perseverance Rover. Perseverance will study clay-rich deltaic units and chemical sedimentary rocks deposited at the margin of a paleolake in Jezero Crater, hoping that they will yield informative evidence for past environmental conditions, and evidence for life itself. Fluvial and lacustrine rocks in Earth’s geological record are driving the exploration of these exciting Martian deposits. Well-preserved Archean river and lake systems in Western Australia are providing a valuable depositional analogue for a closed basin that may also have developed on a microbially-dominated planet, several billion years ago.
Along with modern and other ancient analogues, Australian fluvio-lacustrine systems preserved in the Neoarchean Fortescue Group have been used to develop an exploration model for microbial biosignatures sought by upcoming Mars missions. In the Fortescue Group, the greatest abundance and diversity of macroscopic biosignatures is found at the upper contacts of regressive lithostratigraphic cycles and at lake peripheries. Macroscopic biosignatures such as stromatolites can in turn be used to target fine-scale lithochemistry instruments, for example those carried on the robotic arm of Perseverance, and the drilling/caching of samples that will be returned to Earth for study in laboratories.
David is an astrobiologist focused on palaeoenvironments of the early Earth and Mars. He completed a postdoc at Caltech before joining NASA’s Jet Propulsion Laboratory in 2015. He’s a Long Term Planner for NASA’s upcoming Perseverance Rover mission, and a Co-Investigator for an instrument on the rover’s robotic arm.