NASA Orbiter Shines New Light on Martian South Pole Mystery
NASA’s Mars Reconnaissance Orbiter (MRO) has recently revisited a long-standing enigma beneath the thick ice of Mars’ south polar region. Using an innovative radar technique, the orbiter has provided fresh insights that challenge earlier interpretations of this mysterious feature. Previously thought to be an underground lake, new data suggest that this area is more likely composed of rock and dust layers buried beneath miles of ice.
The original discovery in 2018, made by the European Space Agency’s Mars Express orbiter, sparked significant excitement because the presence of liquid water on Mars is closely linked to the possibility of life. The Mars Express team detected a strong radar signal near the south polar ice cap, which they interpreted as evidence of a subsurface lake. However, the latest study, led by scientists Gareth Morgan and Than Putzig from the Planetary Science Institute, used enhanced radar observations from MRO to reassess this claim. Their findings, published in Geophysical Research Letters on November 17, 2025, indicate that the feature is unlikely to be liquid water.
Advanced Radar Techniques Reveal Subsurface Composition
The key to this new understanding lies in a special maneuver performed by MRO, where the spacecraft was rolled 120 degrees. This “very large roll” allowed the orbiter’s Shallow Radar (SHARAD) instrument to send a stronger signal deeper beneath the surface, resulting in clearer images of the subsurface layers. Because SHARAD’s antenna is located at the back of the spacecraft, the orbiter’s body normally blocks some of the radar signal, reducing its sensitivity. The roll maneuver was carefully planned and executed by engineers at NASA’s Jet Propulsion Laboratory and Lockheed Martin Space to overcome this limitation.
On May 26, 2025, SHARAD successfully detected a faint radar reflection from the target area, which spans approximately 12.5 miles (20 kilometers) and lies under nearly a mile (1,500 meters) of water ice. Unlike the strong, mirror-like reflection expected from liquid water, the signal was weak, suggesting a different composition. This contrasts with the 2018 Mars Express observations, which showed a bright signal that had been interpreted as a briny lake—water with high salt content that could remain liquid under extreme cold.
Morgan and Putzig noted that despite nearly 20 years of SHARAD observations, no strong signals had been detected from this depth until the very large roll was performed. Additionally, a similar roll over an adjacent area failed to detect any signal, indicating that the original bright radar reflection is unusual and may not be caused by liquid water.
NASA Orbiter Shines New Perspectives on Mars’ Subsurface Resources
While the new data make it difficult to support the idea of a liquid water lake beneath Mars’ south pole, the radar technique itself holds great promise for future exploration. The south polar ice cap rests on heavily cratered terrain, and the bright signal detected by Mars Express might instead come from a rare smooth surface, such as an ancient lava flow.
Morgan, Putzig, and their team are eager to apply the very large roll technique to other intriguing regions on Mars. One such location is Medusae Fossae, a vast geological formation near the Martian equator that produces little radar reflection. Scientists have debated whether this formation consists of volcanic ash layers or contains significant ice deposits deep underground. If ice is present near the equator, it could provide valuable water resources for future human missions, as this region receives more sunlight and offers a warmer environment for astronauts.
The Mars Reconnaissance Orbiter, managed by NASA’s Jet Propulsion Laboratory and built by Lockheed Martin Space, has been orbiting Mars since 2006. Its SHARAD instrument, provided by the Italian Space Agency, continues to enhance our understanding of the Red Planet’s subsurface. By shining new light on Martian mysteries, NASA’s orbiter is helping to pave the way for future exploration and discovery.
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Source: original article.