Spacecraft 'Sees' the Mysteries Buried Under the Polar Ice Caps of Mars
Mars' south pole as seen by Mars Express.
Credit: ESA

Like Earth, Mars possesses north and south polar ice caps. Unlike Earth, however, the Martian versions not only contain water ice, there's there's a thick layer of carbon dioxide ice acting as a blanket. Frozen CO2, also known as "dry ice", is known to wax and wane in thickness depending on the Martian season. Though we have a pretty good understanding of the ice caps' surface features and how they interact with Mars' predominately carbon dioxide atmosphere, what lies beneath the most ancient layers of ice has been a mystery.

That was, however, until NASA's Mars Reconnaissance Orbiter (MRO) arrived in orbit in 2006.

On board the veteran Mars satellite is an instrument called SHARAD — short for "Shallow Radar" — that has been bouncing radio waves off the planet's surface for over a decade. Individual observations by the instrument, for 2,000 orbits over the poles, have revealed some interesting icy findings over the years, but now, with a huge archive of data, planetary scientists have been able to build a 3-D view of the ice covering the north and south poles in the hope of better understanding the structures we cannot see inside the ice and how the ice changes over time. With this information they hope to build a picture of climatic changes over millions of years.