In the northern part of Arabia Terra, there are fields that look like a giant brain: ridges and troughs wind like convolutions. On Earth, similar patterns form in cold regions when water in the soil freezes and thaws, causing stones to sort themselves into stripes. But the Martian ridges are taller — averaging 3.29 meters — while Earth's mechanisms produce less than half a meter.
The scientists built a computer model that simulates these processes. The model reproduced the pattern shapes accurately — deviation less than 15%. But it fell short on ridge height: stone sorting alone can't lift them above half a meter. The missing nearly three meters, according to calculations, were carved by ice: it sublimated in the dry air, causing the ground to sink in the troughs and making the ridges relatively taller.
So the patterns became a climate record. First, water in the ground froze and thawed — meaning it was wet. Then ice began to sublimate, turning directly from solid to vapor — the climate became dry and cold. Over the last three million years, Mars has lost about three meters of subsurface ice. The brain-like patterns are actually a memory of the planet drying out.
The ridges in these patterns are as tall as a one-story house, while the neighboring troughs are shallower than a person's height.
In Kim Stanley Robinson's novel 'Red Mars,' colonists try to warm the planet, but its ancient dry climate reminds them how hard it is to keep water on Mars.