August 12, 2013
Mars Express Offers Peek Beneath Martian Surface
Brett Smith for redOrbit.com - Your Universe Online
Using ground penetrating radar, the spacecraft was able to image the composition of Mars several miles below the surface, revealing various layers of ice, dust and rock. The image essentially revealed a 3,500-mile slice through the planet’s southern highlands region that extended all the way to the planet’s southern polar region.
To create the image, the orbiter sent low-frequency radio waves at the planet’s surface. Although the majority of the radar waves were reflected away by the planet’s surface, some penetrated deeper and bounced off lower layers of material found below the surface.
Based on the strength and timing of the returning radar signals, Mars Express was able to determine the depths and types of underground interfaces. The image was created using the craft’s Mars Advanced Radar for Subsurface and Ionospheric Sounding instrument just after it became operational in 2005.
On the right side of the image, a dipping line represents the planet’s Hellas Basin. At 4.3 miles deep and about 1,400 miles wide, it is one of the largest impact basins in our solar system. Just left-of-center, a bright mass represents the planet’s southern pole region.
The visual representation of the polar region was created when radar penetrated beneath the pole’s cap of frozen carbon dioxide and water, revealing several layers of ice and dust. These layers, which extend almost 2.5 miles below the surface, are known as the South Polar Layered Deposits. They are thought to be the result of variations in the deposition of polar ice and dust as Mars went through several cycles of climate change. The radar indicated that the amount of water trapped in the southern polar region would cover the entire planet in 36 feet of water.
Named after its streamlined production process, the Mars Express marked its tenth anniversary in space this past June. After arriving at the Red Planet in December 2003, mission scientists experienced their most devastating setback to date – an on-board landing craft was released to the surface and never heard from again.
However, a camera installed on the Mars Express with the sole purpose of tracking the lander’s release has provided some of the spacecraft’s most stunning images. ESA scientists have been posting images online from the "ordinary camera in an extraordinary place” over the past few years.
In December 2012, images from orbiter’s more sophisticated stereo camera revealed a southern mountain range covered in carbon dioxide frost and other surface features such as ancient craters surrounded by ejected material. When the Martian surface was struck by an asteroid or meteor, material known as ejecta essentially created a plateau around the impact crater.
“The ejecta surrounding pedestal craters form erosion-resistant layers, meaning that the immediate vicinity around the crater erodes more slowly than the surrounding terrain,” the agency explained on its website. “The resistant ejecta layer is largely untouched, forming the pedestal.”
Images from the Mars Express, like those from NASA’s Curiosity rover, have also shown evidence of surface water flowing across the planet’s surface.