Analysis indicates no subglacial lake on Mars

The Martian polar ice caps are composed of layers of water ice and frozen carbon dioxide (dry ice). These layers can exhibit minor variations in composition and thickness, which play an important role in the radar interference phenomenon observed by planetary scientists.

Researchers at Cornell University have conducted extensive simulations to model the layering scenarios within the Martian south polar ice cap. The simulations varied the composition and spacing of the ice layers, taking into account the known conditions and materials present on Mars.

The key findings from these simulations are:

• The assumptions about the presence of frozen carbon dioxide layers below the ice cap were likely incorrect.
• Even small changes in the composition and thickness of the water ice layers can significantly impact the radar signals reflected from these layers.
• Thousands of random layering scenarios were modeled, and many of them produced bright subsurface signals consistent with the observations made by the MARSIS radar instrument on the Mars Express orbiter.

The simulations suggest that the bright radar reflections initially thought to indicate the presence of a subglacial lake can be explained by the constructive interference of radar waves due to the varying ice layer properties. This phenomenon, known as thin-layer interference, is a more plausible explanation for the observed signals without the need to invoke the existence of liquid water.

The radar interference analysis conducted by the Cornell University researchers provides a compelling explanation for the bright radar reflections observed beneath the Martian south polar ice cap. By simulating thousands of random layering scenarios, the team demonstrated that even minor variations in the composition and thickness of the water ice layers could lead to constructive interference of radar waves.

This interference phenomenon, known as thin-layer interference, can create bright subsurface signals that mimic the characteristics of those initially interpreted as evidence for a subglacial lake. The simulations revealed that these bright reflections are not confined to a single location but can occur scattered across the entire south polar layered deposits.

One of the key insights from the simulations is that the assumptions about the presence of frozen carbon dioxide (dry ice) layers below the ice cap were likely incorrect. Instead, the researchers found that the observed radar signals could be produced by varying the properties of the water ice layers alone.

The radar interference analysis offers a more plausible and simpler explanation for the observations made by the MARSIS radar instrument on the Mars Express orbiter. By accounting for the known materials and conditions on Mars, the simulations eliminate the need to invoke the existence of liquid water to explain the bright radar reflections.

While the possibility of future detections by more advanced instruments cannot be ruled out, the researchers suggest that the potential for liquid water and life on Mars might have ended long ago. The interference phenomenon, driven by the natural variations in the ice layers, provides a compelling alternative to the subglacial lake hypothesis.