Science & Environment

Mosaic image reveals Martian glory

HRSC mosaic Image copyright Other

Scientists in Germany have pieced together a stunning mosaic image of the Martian surface.

The global "atlas" was painstakingly constructed from pictures sent back by a camera instrument on Europe's Mars Express spacecraft, which is in orbit around the Red Planet.

The detailed mosaic should help better inform the selection of landing sites for future Martian missions.

It is the work of a team at the Freie Universit├Ąt Berlin.

Lead author Dr Patrick McGuire recently presented the mosaic at the Mars 8 meeting in Pasadena, California. This version had a resolution of about 475m per pixel in a file that's about 1GB in size. This, he said, made it "manageable to download or study".

But Dr McGuire and colleagues Prof Stephan van Gasselt, Sebastian Walter and others want to ultimately push the resolution down to 12.5m per pixel - which would make it one of the most detailed semi-global representations of Mars available.

"To be able to view some of the geomorphological features at a resolution of 12.5m per pixel together with their regional and global context would be quite an advance," Dr McGuire said.

Mars Express was launched in 2003 on a mission to gather scientific measurements of Mars' atmosphere, surface and subsurface.

Prof van Gasselt said the work would bridge a gap between older mosaics of the Martian surface and even higher resolution data from newer spacecraft that would become available in future.

For the current version, the team used around 2,200 images of the surface captured by the High Resolution Stereo Colour Camera (HRSC) carried aboard Mars Express (MEx).

In addition to increasing the mosaic resolution, the team also has plans to combine the mosaic with data from another MEx instrument called Omega, which has been used to map the variety of minerals in Martian surface rocks.

At the moment, the team is principally using the Omega data to help correct variations in the brightness of the images that make up the Martian mosaic - something that's known as radiometric control. These variations have already been corrected for in the Omega data.

But eventually, the high-resolution mosaic could provide important geomorphological context for the mineral make-up of rocks on Mars.

Image copyright Esa
Image caption Researchers are also working on a 3D terrain model of Mars

Prof van Gasselt said that correcting global illumination variations was straightforward, but one of the big unknowns was how the Martian surface reflected light on a local scale. "On Mars, there are no water surfaces, there is no vegetation; still, there are different surface units that reflect light in different ways and behave differently. Nobody knows this," he told BBC News.

He added that the team was changing assumptions in its computer algorithms to try to better address some of these questions.

Another team at the university is working to build a 3D terrain model of Mars in collaboration with researchers at the German space agency (DLR).

Having as much data as possible to support the selection of landing sites on Mars will be vital over the next few years.

The European Space Agency plans to send two landers to Mars this decade: a demonstrator in 2016 and a rover in 2018. Nasa wants to send a separate rover to Mars in 2020. Its design would be inspired by that of Curiosity, but would carry a different scientific payload.

Also presented at the Mars 8 conference was a new geological map of Mars constructed by Ken Tanaka of the US Geological Survey (USGS) and colleagues from the US, Germany and Japan. The map combines 16 years of data from four orbiting spacecraft, and features interpretations of Martian regions with different geological character.

And additionally, a further mosaic of the Red Planet pieced together data from the Themis instrument aboard Nasa's Mars Odyssey probe.

More on this story