Mars radar opens up a planet’s third dimension

ESA’s Mars Express radar sounder, MARSIS, has looked beneath the martian surface and opened up the third dimension for planetary exploration. The technique’s success is prompting scientists to think of all the other places in the Solar System where they would like to use radar sounders.

No matter how accurate a camera is, it can only map a planet’s surface. To retrieve information about the underground realm, planetary scientists in the past would have thought it necessary to land on the surface and start digging. But that would only be good for a single spot on a large planet and the first few decimetres of the surface.

To get the global picture of the subsurface they need a radar sounder, such as the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS), to find the best spots for the future landers to go and dig.

MARSIS was an experiment in every sense of the word. “It was a leap into the unknown,” says Ali Safaeinili, MARSIS co-investigator at the Jet Propulsion Laboratory (JPL), California, USA.

No one had ever used a radar sounder from orbit on another planet before. So the team could not even be sure whether it would work as planned. The subsurface of the planet might have been too opaque to the radar waves or the upper levels of martian atmosphere (ionosphere) might have distorted the signal too much to be useful. Thankfully, none of this happened.

“We have demonstrated that the polar caps at Mars are mostly water ice, and produced an inventory so now we know exactly how much water there is,” says Roberto Orosei, MARSIS Deputy Principal Investigator, IASF-INAF, Italy.

Armed with a better understanding of how planetary radar sounders work, the MARSIS team is beginning to look further afield in the Solar System, to other bodies that might benefit from radar investigation. One obvious target is Jupiter’s icy moon, Europa.

A MARSIS-type experiment in orbit around Europa could probe its icy crust to help understand the puzzling features we see on the surface. It may even see the interface at the bottom of the ice where an ocean is expected to begin.

At Saturn’s moon, Titan, penetrating radar could be used to measure the depths of the hydrocarbon lakes that the Cassini spacecraft has detected. It could also probe the structure beneath the enigmatic geysers that Cassini has observed on another one of Saturn’s satellites, Enceladus. “Radar sounders are very well suited to exploring icy worlds,” says Orosei.

But not just for icy moons. Asteroids and comets could be thoroughly scanned by a radar sounder, producing three-dimensional maps of their interior – perhaps exactly the data we will need if, one day, we have to nudge one out of Earth’s way.

MARSIS has served as an excellent example of international collaboration between Europe and America. Increasingly, such collaborations are set to become a positive feature of our joint exploration of space.

Source: ESA

Related stories:

Icy Promethei Planum
Promethei Planum, an area seasonally covered with a more than 3500 m thick layer of ice in the martian south polar region, was the subject of the High Resolution Stereo Camera’s focus on 22 September 2005 as Mars Express was in orbit above the Red Planet.
ESA presents Mars in 3D
Mars is about to come into 3D focus as never before, thanks to the data from the Mars Express High Resolution Stereo Camera (HRSC). A new high-resolution Digital Terrain Model data set that has just been released onto the Internet, will allow researchers to obtain new information about the Red Planet in 3D.
Mars Express - 5000 orbits and counting
On 25 December 2003, Europe’s first Mars explorer arrived at the Red Planet. Almost four years later, Mars Express continues to rewrite the text books as its instruments send back a stream of images and other data. Today, the spacecraft reached another milestone in its remarkable career by completing 5000 orbits of Mars.
Mars Express Probes Red Planet's Unusual Deposits
The radar system on the European Space Agency's Mars Express orbiter has uncovered new details about some of the most mysterious deposits on Mars: the Medusae Fossae Formation. It has provided the first direct measurement of the depth and electrical properties of these materials, providing new clues about their origin.
Mars Express radar gauges water quantity around Mars south pole
The amount of water trapped in frozen layers over Mars' south polar region is equivalent to a liquid layer about 11 metres deep covering the planet.
Geologists finding a different Mars underneath
Scientists are finding an older, craggier face of Mars buried beneath the surface, thanks to pioneering sounding radar co-sponsored by NASA aboard the European Space Agency's Mars Express spacecraft.
Mars Express and the story of water on Mars
For a number of decades now, astronomers have wondered about water on Mars. Thanks to ESA's Mars Express, much of the speculation has been replaced with facts. Launched on 2 June 2003, Mars Express has changed the way we think of Mars.
Mars echo from Italian radar reported
Italian and U.S. space agency officials say they've received the first signals from an Italian radar orbiting Mars to search for water or ice on the planet.

News discussion:

Space & Earth science news