NASA Orbiter Penetrates Mysteries Of Martian Ice Cap

NASA Orbiter Penetrates Mysteries Of Martian Ice Cap

This image, combining data from two instruments aboard NASA's Mars Global Surveyor, depicts an orbital view of the north polar region of Mars.

The ice-rich polar cap (the quasi-circular white area at center) is approximately 1,000 kilometers (621 miles) across. The white cap is riven with dark, spiral-shaped bands.

These are deep troughs that are in shadow. They do not reflect sunlight as well or have more internal layers exposed.

To the right of center, a large canyon, Chasma Boreale, almost bisects the ice cap. Chasma Boreale is about the length of the United States' famous Grand Canyon and up to 2 kilometers (1.2 miles) deep.

New findings from the shallow radar instrument aboard the Mars Reconnaissance Orbiter have revealed subsurface geology in this region, allowing scientists to reconstruct the formation process of the large chasm and spiral troughs (see PIA13164).

The image synthesizes topographic data from Mars Orbiter Laser Altimeter (MOLA) and images from the Mars Orbiter Camera (MOC). Mars Global Surveyor, launched in 1996, operated longer at Mars than any other spacecraft in history.

It went silent in November 2006, after gathering data at Mars for more than four times as long as originally planned. Image Credit: NASA/JPL-Caltech/MSSS. For a larger version of this image please go here.

MARS Reconnaissance Orbiter
Data from NASA's Mars Reconnaissance Orbiter have helped scientists solve a pair of mysteries dating back four decades and provided new information about climate change on the Red Planet.

The Shallow Radar, SHARAD, instrument aboard the Mars Reconnaissance Orbiter revealed subsurface geology allowing scientists to reconstruct the formation of a large chasm and a series of spiral troughs on the northern ice cap of Mars.

"SHARAD is giving us a beautifully detailed view of ice deposits, whether at the poles or buried in mid-latitudes, as they changed on Mars over the last few million years," said Rich Zurek, Mars Reconnaissance Orbiter project scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif.

On Earth, large ice sheets are shaped mainly by ice flow. According to this latest research, other forces have shaped, and continue to shape, polar ice caps on Mars. The northern ice cap is a stack of ice and dust layers up to two miles deep, covering an area slightly larger than Texas. Analyzing radar data on a computer, scientists can peel back the layers like an onion to reveal how the ice cap evolved over time.

One of the most distinctive features of the northern ice cap is Chasma Boreale, a canyon about as long as Earth's Grand Canyon but deeper and wider. Some scientists believe Chasma Boreale was created when volcanic heat melted the bottom of the ice sheet and triggered a catastrophic flood. Others suggest strong polar winds carved the canyon out of a dome of ice.

Other enigmatic features of the ice cap are troughs that spiral outward from the center like a gigantic pinwheel. Since the troughs were discovered in 1972, scientists have proposed several hypotheses about how they formed. Perhaps as Mars spins, ice closer to the poles moves slower than ice farther away, causing the semi-fluid ice to crack.

Perhaps, as one mathematical model suggests, increased solar heating in certain areas and lateral heat conduction could cause the troughs to assemble.