The first sample of Martian dirt dumped onto the opening of the Phoenix lander's tiny testing oven failed to reach the instrument and scientists said Saturday they will devote a few days to trying to determine the cause.
Photos released by the University of Arizona team overseeing the mission showed a scoopful of dirt sitting on and around the open oven door after being dumped by the craft's 8-foot robot arm.
But none of it made it past a screen and into the tiny chamber, one of eight on the craft designed to heat soil and test gasses for signs of water or organic compounds that could be building blocks for life.
Nothing seems to be wrong with the dirt delivery by the lander's robot arm, said William Boynton of the University of Arizona in Tucson, who is overseeing the oven experiments.
The dirt landed properly and instruments show a vibrator on the screen designed to help shake soil into the chamber was working.
However, an electronic eye positioned to detect dirt falling into the chamber didn't report any particles.
"We think everything is working correctly, although we don't really know for sure," Boynton said Saturday in a teleconference news briefing from Tucson. "We're a little bit concerned about this but we have some other things to check out."
The teams overseeing the experiments plan to spend the next several days going over possible reasons for the apparent failure, Boynton said.
It could be that the dirt is too dense or compacted to make it past the screen, which is there to allow only small particles into the oven. Or, it could be that incorrect readings from the vibrator made it look like it was working when it was not.
Even if this oven turns out to be unusable, the seven other ovens would be available for the mission's primary experiments.
In the meantime, scientists will turn their attention to using the arm's backhoe-like arm to take close-up photos of the surface and do additional digging.
Phoenix landed in Mars' northern plains on May 25 for a three-month mission. It is not a rover like some Mars missions, and its instruments cannot directly detect past or present life.
The $420 million mission is being overseen by the University of Arizona, with support from NASA's Jet Propulsion Laboratory in Pasadena, Calif.