The European Space Agency's Mars Express orbiter has used its long-wavelength radar tools to probe a mysterious zone near the planet's equator -- and come away with scientists still stumped.
The region in question is called the Medusae Fossae Formation, a series of deposits of material that are thought to be among the youngest on the planet, due to their lack of impact craters. They've puzzled scientists for several reasons, among them their ability to absorb certain wavelengths of Earth-based radar – hence the "stealth" designation.
However, the Mars Express' radar tool uses extraordinarily long wavelengths, of 164 feet to 320 feet or longer, which mostly penetrate the deposits of material and bounce off the rock underneath. This has allowed scientists to determine how deep the material runs, and make some conjectures about its composition.
Some had thought the Medusea formations were simply thin layers over rolling hills. But it turns out the material runs more than 1.5 miles deep in places.
What exactly the formations are made of remains a mystery, however. They exhibit some properties of dust or light volcanic material such as ash. But the material isn't packed or compressed under its own weight, as would be expected.
It offers some resemblance to ice-rich deposits; yet any ice this close to the surface at the equatorial region ought to evaporate away, researchers say. More study is needed. Here's Jeffrey Plaut, the radar system's co-principal investigator at NASA's Jet Propulsion
Laboratory:
Mars Express probes the Red Planet’s most unusual deposits [ESA]
(Image: Topographic images of the divide between Martian highlands and lowlands, where the formations are located. Credit: ESA/ASI/NASA/Univ.
of Rome/JPL/Smithsonian)
