Study: There could be no lake under Mars's ice cap after all

Photo byPhoto by Carles Rabada on Unsplash

Researchers from Cornell University have offered an alternative explanation for the bright radar reflections detected beneath Mars' south polar ice cap, which were initially interpreted as evidence of liquid water. Their simulations indicate that variations in the thickness and composition of water ice layers, which are too subtle for ground-penetrating radar to distinguish, can cause constructive interference between radar waves. This interference can produce reflections with intensity and variability that match the observed data, which were previously thought to suggest the presence of liquid water.

The study proposes that existing ice-layer mechanisms can explain these radar signals without invoking the presence of liquid water. While the discovery of a subglacial lake on Mars would have significant implications for the possibility of microbial life, the researchers suggest that the conditions on Mars—such as temperature and pressure—make the presence of liquid water unlikely. Their model, published in Science Advances, shows that variations in ice layers can generate radar reflections similar to those detected by the Mars Express orbiter's radar instrument without needing a liquid lake.

The researchers used realistic models of ice layers, varying their composition and spacing to replicate the radar observations. Their findings indicate that the bright radar signals could result from radar waves bouncing off closely spaced layers, creating amplified reflections. This hypothesis provides a straightforward explanation for the observations, aligning with known conditions at the Martian poles.

While the study does not entirely rule out the possibility of liquid water, it suggests that the idea of a subglacial lake may not be accurate. The researchers believe that the excitement over potential liquid water may be misplaced, given the conditions on Mars.