When scientists use radio waves to peer under the ice cap at Mars’ south pole, they have no idea what they’re seeing. There is certainly something odd there. When the first images of the objects appeared three years ago, astronomers thought they were lakes – miles-long stretches of liquid water hiding beneath the Martian surface.

Now they’re not so sure. New data released this week by researchers at NASA’s Jet Propulsion Laboratory suggest the things are too near the surface to be liquid water. They sit at a depth where the temperature is minus 81 degrees Fahrenheit. Even salty water should be frozen in those conditions. Yet there they are, a tantalizing hint of a discovery that could hold alien life or otherwise reshape our understanding of Mars – or be nothing of consequence, really.

When Italian astronomer Giovanni Schiaparelli mapped Mars’ surface in 1877, he found curious formations he called “canals.” What were they? How did they form? The finding fascinated scientists and generations of science fiction writers in ways that still color our romance with the red planet. Discovery is science’s aim. But mystery is its allure.

Do lakes lie under the surface of the Martian south pole? Some day, surely, we will know. But for now, the only answers are left to the imagination.