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Mars' poles shrink during ice ages, boffins say

Yes we do mean shrink: Martian cold snaps shift ice closer to the equator

New analysis of Mars' poles suggest they get bigger when the red planet's not experiencing an ice age.

A new paper, An ice age recorded in the polar deposits of Mars, reaches that conclusion after analysing data from the Mars Reconnaissance Orbiter's Shallow Subsurface Radar (SHARAD).

As NASA explains, during Martian ice ages the planet's “... poles become warmer than lower latitudes. During these periods, the polar caps retreat and water vapor migrates toward the equator, forming ground ice and glaciers at mid-latitudes.”

“As the warm polar period ends, polar ice begins accumulating again, while ice is lost from mid-latitudes.”

On Earth, things are the other way around: the poles get cold, water concentrates there and form ice sheets that head towards the equator. During temperate periods, such as the current epoch, the poles warm and shrink but the oceans expand.

The new evidence collected by SHARAD shows that Mars' poles are currently growing and have likely added about 300m depth – for a total 87,000 cubic kilometres – of ice since the last ice age ended around 370,000 years ago. Layers in the ice give the game away.

It's hoped that the new theory developed using SHARAD images helps us develop a better understanding of the Martian climate, how it impacted the planet's evolution into its current arid state and perhaps also offers some insights into our own blue marble.

NASA's especially chuffed by the study because, among other things, it shows that the ten-year-old Mars Reconnaissance Orbiter remains in fine fettle. ®

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