Aug 6, 2007
AFM takes off for Mars
Phoenix, a new NASA mission to Mars that will analyse soil on the red planet in the most detail yet, has taken off from Cape Canaveral. The spacecraft carries several sophisticated instruments, including a new remotely-controlled atomic force microscope (AFM) that can resolve details as small as 200 nm. Results from the spacecraft, expected to land on Mars at the end of May 2008, should tell us whether the planet holds life – or whether it once did.
When it lands on the North Pole of the planet, Phoenix, an international collaboration led by the University of Arizona in the US, will deploy a trenching tool that can dig half a metre into the ground. This is much deeper than the few centimetres achieved in previous missions such as the Mars Rovers and Viking. The spacecraft also carries a weather station and two microscopes – an optical microscope with its own light source and a high-resolution AFM that could also contribute to detecting the presence of water.
"What we are looking for are 'fingerprints’ of water in the Martian dust and soil particles," AFM project leader Urs Staufer from the University of Neuchâtel in Switzerland told nanotechweb.org. "The texture of particles exposed to water will be different to those generated by rocks just crumbling down. Certain minerals exposed to water are locally attacked, leaving behind etch-pits and the size distribution of particles the AFM finds will also indicate whether fluidic transport occurred."
The new AFM, dubbed FAMARS (First AFM on MARS), has a high resolution and can measure real 3D topography. The instrument contains eight small tips attached to flexible levers. If one of these tips, which will scan the Martian soil during measurements, is damaged during the mission, another will take its place. The instrument's motion will also be damped using internal friction of its suspension system to avoid "mechanical ringing".
During operation, highly energetic ions from outer space can temporarily generate short-cuts (or "latch-ups") inside the instrument's electronic chips, which would cause a current surge that burns the components. To overcome this, the FAMARS scientists will constantly monitor the power lines of the controller using a small circuit that is built from radiation hard material. "As soon as the current gets too high, we switch off the electronics within a fraction of a second," says Staufer.
Another potential problem is the loss of data in temporary registers, adds Staufer. This is overcome by storing the data in three registers at the same time instead of just in one. "It is unlikely that all three cells will get hit by an energetic ion, so the risk of losing data is highly reduced," he explains.
The $420 m Phoenix mission is so-called because it rose from the ashes of two earlier failed Mars missions. Its lander was originally built for the Mars Surveyor mission, planned for 2001 but later cancelled by NASA. Many of its instruments were built or designed for the Mars Polar Lander, which was lost as it entered Mars' atmosphere in 1999.
The team says it is now relaxing for a few days after the successful launch of Phoenix this Saturday atop a Delta II rocket. "We will then continue practicing operations," says Staufer. "This will be a very critical phase where we have to learn how to remotely operate the whole spacecraft."
About the author
Belle Dumé is contributing editor at nanotechweb.org