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The Utopia Planitia region of Mars is thought to be the location of an ancient ocean, as suggested by recent studies. Historical data from NASA’s Mariner 9, which captured images in the 1970s, first indicated that water shaped the Martian landscape, providing critical evidence that the planet once hosted liquid water.
Over the years, research has continuously unveiled that water was a significant factor in Mars’ early history. For instance, studies of Martian meteorites have indicated the presence of water dating back 4.5 billion years. More recently, impact craters formed in the last few years reveal the existence of subsurface ice today, demonstrating that water is still a relevant topic of interest regarding Mars.
The current discourse revolves around the timeline of water’s presence, its volume, and its duration on the planet. A particularly intriguing question is whether Mars ever had oceans. A new study published in the journal PNAS on February 24 has sparked significant discussion. The research team, led by Jianhui Li from Guangzhou University in China, utilized data from the China National Space Administration’s Zhurong rover to investigate this question.
Evidence of Water on Mars
The Zhurong rover has provided unique insights into rocks buried near a proposed ancient shoreline, revealing possible beach deposits from a former Martian ocean. This finding aligns with the notion that Mars may have once been covered by significant bodies of water.
An imaginative reconstruction of Mars 3.6 billion years ago, depicting an ocean that could have spanned nearly half of the planet. The orange star marks the landing site of the Zhurong rover, while the yellow star indicates where NASA’s Perseverance rover is located. Robert Citron/Southwest Research Institute/NASA
Rovers such as Zhurong and the NASA Perseverance rover play crucial roles in studying the Martian environment, focusing on the geology, soil, and atmosphere, and searching for indicators of past water presence, which is essential for determining the planet’s potential to support life. Sedimentary rocks are of particular interest because they hold clues about ancient water and, consequently, the possibility of life on Mars.
The Perseverance rover is currently exploring a delta deposit thought to be connected to an ancient lake within the 30-mile-wide (45 km) Jezero impact crater. In contrast, Zhurong is analyzing remnants of an ocean in the northern Martian hemisphere, specifically in Utopia Planitia.
A Historical Perspective
Named after the mythical god of fire, the Zhurong rover was launched by the Chinese National Space Administration in 2020 and operated on Mars from 2021 to 2022, with its landing site located in Utopia Planitia—Mars’ largest impact basin, spanning about 2,050 miles (3,300 km).
In its exploration, Zhurong has been investigating an area characterized by paleoshorelines, which are believed by some researchers to represent the remnants of a global ocean that might have enveloped the northern hemisphere of Mars. However, there exists ongoing debate among scientists regarding this interpretation, highlighting the need for further observation and study.
On Earth, oceanic geological records are clear and varied, indicating that while modern oceans are young, older ocean deposits can be several billion years old. Understanding these geological characteristics is essential for interpreting Martian history.
A diagram illustrating how a series of ancient beach deposits may have formed at Mars’ Zhurong landing site. Credit: Hai Liu/Guangzhou University
Characterization of Mars’ Subsurface
The Zhurong rover systematically gathered data along a 0.8-mile (1.3 km) transect positioned perpendicular to the paleoshoreline. The primary objective was to analyze the rock types present and the historical narrative they convey.
Utilizing ground-penetrating radar, Zhurong investigated depths of up to 328 feet (100 m) below the surface, revealing various features of the buried rocks, including their orientation and layering. The radar data uncovered reflective layers indicating sedimentary rock formations that align with how sediments are deposited in oceanic environments on Earth.
Analysis showed that these rocks exhibited characteristics consistent with being sedimentary rather than volcanic, reinforcing the idea that Zhurong may have indeed found coastal deposits linked to an ancient ocean.
Through comparative analysis with terrestrial sedimentary environments, the findings underscore that the rocks imaged by Zhurong are similar to those found near coastal regions on Earth, supporting the hypothesis that they represent a Martian beach.
Insights into Mars’ Wet History
A photograph of frost-covered terrain in Utopia Planitia, taken by the Viking 2 lander in 1979. NASA/JPL
The Noachian epoch, spanning 4.1 billion to 3.7 billion years ago, is regarded as a period of abundant water on Mars, illustrated by extensive valley networks and mineral maps reflecting surface water. However, evidence for surface water during the subsequent Hesperian period, from 3.7 billion to 3 billion years ago, is less definitive. While vast outflow channels appear to have been formed due to dramatic groundwater releases, this suggests a shift toward a drier Mars during the Hesperian.
Nevertheless, findings from Zhurong regarding coastal deposits could imply the existence of stable surface water for a longer duration than previously understood, potentially extending into the Late Hesperian period. This raises the possibility that habitable environments associated with Martian oceans existed further into the planet’s past than earlier theories suggested.
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www.astronomy.com