The universe still has much to teach us
Fresh evidence indicates that liquid water remained on the Martian surface hundreds of millions of years longer than scientists had previously assumed. The conclusion comes from an analysis of data gathered by China's Zhurong rover, carried out by a team led by Jiachen Liu of the University of Hong Kong. They found selenite formations in Utopia Planitia and published their findings in Nature Astronomy, dating the surface in that area to roughly 757 million years old. For the minerals preserved in the rocks to have formed, the researchers say, a water reservoir between 6.25 and 25 meters deep must have existed.
Older theories held that Mars's surface froze solid around 3 billion years ago. Zhurong landed in Utopia Planitia in May 2021 and collected observations for 93 days before a dust storm forced an end to its mission in 2022. Along the way, the rover detected bright, flat rocks heavily enriched in water-bearing minerals.
What this means for science
The structures in these stones are made of selenite, a coarse crystalline form of gypsum, and their formation would have required crystallization from highly concentrated salty brine. To fix the age of the site, researchers counted impact craters. They also suggest that subsurface saltwater may have moved upward as volcanic heat drove it toward the surface.
Such results could reshape accepted ideas about the history of water on Mars and how it influenced planetary development. They add fresh detail to our picture of Martian geology and climate, and they raise intriguing questions about whether this wetter, later Mars could have supported habitable conditions.
The discoveries from Zhurong's data highlight how much more we need to learn about Mars, both to reconstruct its past and to search for environments that might once have favored life.
Finding liquid water from a later period than expected may also guide planning for upcoming missions focused on Martian climate and geology. The report encourages researchers to reconsider longstanding assumptions about planetary evolution in settings once judged too harsh for life.
These findings not only challenge previous assumptions about the Martian climate but also resonate with recent discoveries of water remnants in ancient volcanoes on Mars, suggesting a more complex history of water and volcanic activity on the planet than previously thought.