Mars Layers Suggest Ancient Groundwater

HiRISE images of Arabia Terra show regular, coral‑reef‑like stacks of sedimentary layers whose patterning implies repeated environmental cycles — likely episodes of dust storms interacting with near‑surface groundwater — before Mars dried out. If confirmed by in‑situ sampling, these layers would mark a previously underappreciated style of climate variability and near‑surface hydrology on Mars. — This reframes where and how missions should search for traces of past habitability on Mars and influences funding, planetary‑protection decisions, and public expectations about life‑search prospects.