China’s Zhurong rover, part of the Tianwen-1 mission, has uncovered compelling evidence that Mars may have once hosted a vast ocean. This groundbreaking discovery was made in southern Utopia Planitia, a plain in the planet’s northern hemisphere. Researchers from Hong Kong Polytechnic University, the China Academy of Space Technology, and the Russian Academy of Sciences suggest that this region might have been a coastline of an ancient sea that existed around 3.68 billion years ago. The findings, published in Scientific Reports and Nature, bolster decades of speculation about Mars’s watery past.
Divided Landscape
The team identified distinct topographic features in southern Utopia Planitia, dividing the area into three sections with varying depths: shallow marine, deep marine, and a nearshore zone. The shallow marine unit in the south, with less water or ice content, contrasts with the deeper, ice-rich northern section. This variation suggests the presence of a shoreline where water once lapped, forming sedimentary deposits. The estimated depth of the shallow ocean was up to 600 meters, but data remains insufficient to determine the full depth of the deeper marine unit.
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Geological Clues to a Frozen Ocean
Key features like pitted cones, polygonal troughs, and etched flows provided evidence of the region’s watery history. Pitted cones, possibly formed by mud volcanoes, often emerge in areas with low groundwater or ice content. Polygonal troughs and etched flows, on the other hand, are linked to water or ice-rich environments. According to lead author Wu Bo, the area’s geological characteristics strongly indicate past water activities, marking it as a nearshore zone. The researchers also noted a 4.2-kilometer topographic contour line, aligning with the water level line, further supporting the ancient shoreline theory.
Ocean’s Lifecycle
The researchers propose that flooding created this ocean approximately 3.68 billion years ago. Over time, the water likely froze, creating a short-lived coastline before disappearing entirely by 3.42 billion years ago. Sediments deposited during this period were preserved in the shallow and deep marine units, offering a rare glimpse into the ocean’s evolutionary history. This rapid freeze and disappearance might have been triggered by changes in Mars’s climate, atmosphere, or volcanic activity.
Longstanding Debate
For decades, scientists have debated whether an ocean once covered Mars’s northern lowlands. NASA’s Viking 2 mission first mapped the Utopia Planitia region in 1976, and subsequent studies hinted at the possibility of ancient water. However, skepticism remains. Some researchers argue that Mars’s strong winds and erosive forces over billions of years could have erased signs of a shoreline. Others, like planetary scientist Benjamin Cardenas, caution that the findings require further validation, potentially through sample-return missions.
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If confirmed, the presence of an ancient ocean could have profound implications for Mars’s habitability. Water is a key ingredient for life, and a vast ocean raises the possibility that microbial life may have existed on the planet billions of years ago. Understanding the ocean’s history could unlock secrets about Mars’s early climate and its potential to support life. Future missions will aim to test these findings, bringing humanity closer to unraveling the mysteries of the Red Planet.