Zhurong Finds 5-10 cm Selenite Layer on Mars, Pointing to Water 760 Million Years Ago
Updated
Updated · spacedaily.com · Aug 15
Zhurong Finds 5-10 cm Selenite Layer on Mars, Pointing to Water 760 Million Years Ago
1 articles · Updated · spacedaily.com · Aug 15
Summary
A Nature Astronomy study says Zhurong crossed a 5-10 centimetre platy layer in southern Utopia Planitia whose shape and chemistry best match large selenite gypsum crystals.
Infrared bands near 1.45 and 1.95 micrometres and laser detections of sulfur, calcium and hydrogen matched gypsum, while radiating clusters and fishtail-like branching patterns argue for primary evaporite growth rather than later cement or fracture fill.
That interpretation suggests concentrated briny water persisted far later than Mars's early river-and-lake era, with the host resurfacing event dated by crater counts to about 757 million years ago, not by direct crystal dating.
Mass-balance estimates imply at least 6.25-25 metres of cumulative water equivalent, likely supplied episodically to a shallow, possibly ice-covered basin by upwelling groundwater in a cold Amazonian environment.
The study stops short of proving trapped liquid: Zhurong did not observe any fluid inclusions, leaving a future microscopy or sample-return mission to test whether the crystals preserve ancient Martian brine.