Mars sprinkle test yields results

Sprinkling the soil seems to work better than dumping it

Nasa's Phoenix lander will sprinkle Martian soil on to an instrument in an attempt to overcome problems caused by the soil's clumpy nature.

A sample delivered to a mini lab oven on Saturday failed to make it through a sorting screen, and attempts to vibrate the filter have had little effect.

But a test showed that sprinkling soil on to science instruments may work better than dumping it.

Nasa will next try the technique on the lander's optical microscope.

After this, they will sprinkle a sample into one of the seven remaining ovens of an instrument that bakes and sniffs samples, the Thermal and Evolved-Gas Analyzer, or TEGA.

Scientists hope this will yield better results than the previous attempt, when few particles made it through the mesh screen over the opening to the oven.

The sprinkling method was developed a few months ago by members of Phoenix's robotic arm and microscope teams.

It uses vibration of the tilted scoop by a motorised rasp to gently jostle some material out, instead of turning the scoop over to empty it.

The rasp is located on the back of the scoop and will be used later in the mission to scrape up samples of subsurface ice.

The first test of the sprinkling method on Monday produced a layer of fine particles.

"This is good news," said Professor Ray Arvidson of Washington University in St Louis, lead scientist for the robotic arm.

Professor Arvidson said the clumping tendency of Martian soil at the Phoenix site and some earlier landing sites might come from extremely fine particles filling in the gaps between coarser, sand-size particles, perhaps acting together with an unidentified ingredient to cement particles together.

Engineers have noticed an object on the ground near to one of the lander's footpads. They believe it is a spring from the bio-barrier mechanism used to cover the robotic arm and keep it clean in the latter stages of the launch campaign and during flight.

When the bio-barrier - essentially a plastic covering - was removed, it is thought the spring broke away.

Phoenix carries a meteorological station and this has continued to study Mars' weather.