Mars as a time machine to Precambrian Earth

As Mars transitioned from an early Earth-like state to the cold desert planet it is today, it preserved a near pristine record of surface environments in a world without plate tectonics and complex life. The records of Mars’ Earth-like surfaces have remained largely untouched for billions of years, enabling space exploration to provide critical insights about the early days of our own planet. Here, we first review what Mars has taught us about volcanic, tectonic, and metamorphic processes in the absence of discrete plates, drawing comparisons to the terrestrial and venusian records. Then, we summarize advances in understanding its early surface environments, including impact cratering, hydrological, sedimentary, and geochemical processes. Altogether, the martian record provides a picture of early environments that were similar to modern terrestrial ones in many respects, with sediment and geochemical cycling, hydrothermal systems capable of hosting life, but with the exception that topography, sediment, and heat sources were provided by volcanoes and impact cratering rather than plate tectonics. Mars thus offers a lens through which one might catch a glimpse of Earth's infancy, provided exploration efforts continue to refine our understanding of the similarities between Earth and Mars as well as the specificities of each planet.