Clumpy soil on Mars has further hampered the Phoenix lander's attempts to obtain samples for analysis by the spacecraft's test instruments, mission experts said.

"Virtually none of the material made it down into the oven" after the probe dug up new soil clumps from the Martian permafrost with its robotic arm, William Boynton, an investigator for Phoenix's thermal and evolved gas analyser (TEGA), said during a press teleconference.

"We ran a vibrator to help move the soil, we ran it at a higher frequency... (but) we found out today that did not work," Boynton said.

It was a further setback for Phoenix, whose TEGA analyser at the weekend was not able to obtain smaller, testable bits from the Martian landscape which researchers hope will provide clues to whether the planet was once habitable for microbial life.

Between 20 and 30 milligrams of soil is necessary for analysis, but Boynton said less than one milligram of matter passed through the screen into one of the probe's test facilities.

The screen is designed to allow through it particles measuring one millimetre or less. Inside the port there is an infrared beam which determines if particles enter the machine.

Once it gets a sample, the TEGA instrument spends several days analysing its content, first testing for the level of water content, and then heating it gradually to 1000°C to better assess the mineral composition.

Phoenix, which landed on the stark terrain of Mars' north pole region on 25 May, collected the first sample last week on Thursday.

It ain't over yet

The team aims to try the procedure anew in the coming days. Should that fail, mission scientist Doug Ming said, they will attempt a "sprinkle test" in an attempt to jar smaller soil pieces free.

"We hope to deliver a sample in about two sols," or Martian days, Ming said.

Boynton, who is a scientist at the University of Arizona which is coordinating significant elements of the mission, said the team was not urgently pressed for time.

"It will be at least a week or two (of failure) before we start to get terribly concerned," he said.

Phoenix has a total of eight "ovens" that can be used to test separate samples from the Martian surface.

If need be the team can also employ an alternate delivery mechanism which would grind up the sample. "So we are still pretty optimistic that one of these techniques will work for us," Boynton said.

Phoenix is on a three-month mission to inspect Mars' soil for the right combination of water in its ice form and minerals that would demonstrate the planet could or can support basic microbial life.

AFP