Ancient Shoreline Traces in Jezero Crater Expand Mars's Habitability Timeline

Researchers from Imperial College London have found that the ‘Margin unit’ in Mars’s Jezero crater preserves definitive traces of an ancient shoreline. The findings come in the background of data obtained by NASA’s Perseverance rover that revealed evidence of wave-formed beaches and rocks, altered by subsurface water in a Martian crater that once held a vast lake – considerably expanding the timeline for potential habitability at this ancient site.

“Our findings have exciting implications for Mars’s past climate and habitability, while providing new insights into a geologic unit which has long had a debated origin," said lead author Alex Jones, a PhD researcher in the Department of Earth Science and Engineering (ESE) at Imperial.

“Shorelines are habitable environments on Earth, and the carbonate minerals that form here can naturally seal in and preserve information about the ancient environment,” he added.

According to a report put out by the institution, these are compelling indicators that habitable, surface water conditions persisted in the crater (home to a large lake around 3.5 billion years ago) further back in time than previously thought.

Since deployment in 2021, NASA’s Perseverance rover had spent nearly a year extensively exploring the ‘Margin unit’, a geologic unit lining the inner rim of Jezero crater between 2023 and 2024. The unit was a critical target for exploration owing to it being rich in carbonate minerals; these precipitate from liquid water and often trap organic molecules on Earth, making them excellent at preserving any potential biosignatures that are present in the environment.

Before Perseverance’s arrival, the origin of the unit had been contested. Some scientists proposed that it formed as a sedimentary deposit along the edge of the ancient Jezero lake, while others argued it was an igneous rock later altered by water.

In February last year, China's Zhurong rover had found evidence of what looked like sandy beaches from the shoreline of a large ocean that may have existed long ago on the northern plains of Mars.

The findings are the latest evidence indicating the existence of this hypothesized ocean, called Deuteronilus, roughly 3.5 to 4 billion years ago, a time when Mars - now cold and desolate - possessed a thicker atmosphere and warmer climate. An ocean of liquid water on the Martian surface, according to scientists, potentially could have harbored living organisms, much like the primordial seas of early Earth.