Sandstones boasting rounded grains, characteristic cross-bedding, and “ripple” structures have been discovered in Mars’s Jezero crater. On Earth, comparable formations are almost invariably identified as relics of an ancient shoreline. NASA’s Perseverance rover has unearthed the first solid evidence suggesting that the Martian lake possessed a distinct surf zone and that habitable conditions at the water-land interface might have persisted for a longer duration than previously estimated.
These rocks are rich in olivine and carbonates, minerals that materialize through reactions between water and bedrock. On our planet, these often “preserve” chemical signatures of the environment, and occasionally, organic matter. Consequently, this region was designated a primary target for Perseverance’s exploration.
An article published in the Journal of Geophysical Research: Planets detailed how Perseverance dedicated approximately 350 Sols (Martian days) to thoroughly examine this geological stratum. The researchers compiled a mosaic of data, ranging from Mastcam-Z panoramas and 3D models to readings from SuperCam and high-resolution microtexture images captured by the SHERLOC WATSON cameras. The cumulative result of these investigations confirmed: this location within the crater exhibits clear signs of both altered igneous material and sedimentary bodies redeposited within a shoreline environment.
The authors distinguished two primary subunits. The western one appears more massive and exhibits less distinct layering; its origin remains uncertain, though it could be rock formed during magma crystallization. The eastern block, conversely, is characterized by well-stratified sandstones displaying gentle inclinations of layers alternately toward the basin center or the crater rim, featuring characteristic grains, cross-bedding structures, and evidence of erosion surfaces. On Earth, features such as these are typical of nearshore flats and beach bars shaped by wave action.
It is also understood that shoreline regions necessitate relatively consistent, open bodies of water and dynamism capable of sorting and transporting sand—implying not merely a fleeting episode of increased moisture, but a more sustained history for the water body.
The chemical evolution of these rocks is also noteworthy. Olivine crystals in certain areas show significant alteration due to subsurface waters, likely carbonic acid, resulting in the formation of iron and magnesium carbonates.
On Earth, analogous water-rock systems, including hydrothermal ones, are considered potentially habitable, with carbonates acting as excellent “archivists” of environmental conditions.
The discovery in Jezero adds another piece of evidence supporting the concept of a “shoreline” Mars. Furthermore, in 2025, China’s Zhurong rover utilized its subsurface radar to map structures resembling ancient beach deposits at depths of 10–35 meters within the Utopia Planitia region—a hypothetical northern ocean.
Experts at that time suggested that the formation of such bodies required many millions of years, and their buried location had likely shielded them from destruction by wind and erosion.
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