Scientists have known for a while that Mars’ tilt varies wildly over tens of thousands of years, going from being perfectly vertical to having ice buildups at the equator. New research has discovered that these periodic changes have left a trace. They found that ancient ice caps have not disappeared completely but are still there, buried in layers beneath the North Pole.
The new findings are reported in the journal Geophysical Research Letters and detail the so-called cavi unit, a deposit of ice and sand estimated to be hundreds of millions of years old. The ice was organized in slabs with sand, although in certain areas it was 90 percent water by volume. If melted, it would be like having a 1.5-meter (5-foot) layer of water around the Red Planet.
“We didn’t expect to find this much water ice here,” lead author Stefano Nerozzi, a graduate research assistant at the University of Texas Institute for Geophysics, said in a statement. “That likely makes it the third largest water reservoir on Mars after the polar ice caps.”
The discovery was possible thanks to the use of the Shallow Radar instrument onboard NASA’s Mars Reconnaissance Orbiter. It was also independently verified by gravity data of the region, which supports the presence of a vast underground deposit of ice.
The observations might provide a more detailed timeline of Martian glaciation. There are suggestions that despite abundant liquid water, Mars was never a “tropical” paradise and life might have found it hard to evolve in a perennially frigid planet.
“Understanding how much water was available globally versus what’s trapped in the poles is important if you’re going to have liquid water on Mars,” Nerozzi said. “You can have all the right conditions for life, but if most of the water is locked up at the poles, then it becomes difficult to have sufficient amounts of liquid water near the equator.”
The North Pole underground deposit is clearly an important reservoir of water for Mars. Based on the assessment, its volume is equivalent to the combined underground ice deposits found in all the other lower latitudes on the Red Planet.