Efforts to
jiggle a soil sample into one of the instruments on NASA's Phoenix Mars Lander
were unsuccessful, mission scientists said Monday.
Scientists
first attempted to deliver
the first sample of Martian soil to the Thermal and Evolved-Gas Analyzer
(TEGA) Saturday. The instrument is designed to heat up soil samples in its
eight tiny ovens and analyze the composition of the vapors that come off of it.
Though
images relayed back to Earth showed the dirt sitting
on top of TEGA, detectors inside the instrument indicated that none of the
soil particles had fallen through the screen at the entrance to the oven.
"What
we found was that although we had an awful lot of dirt on that screen, almost
none of it made it down into the oven," said TEGA co-investigator William
Boynton, of the University of Arizona.
Mission
scientists have said that the soil probably didn't make it through the screen,
because it "appears to be quite cloddy," said mission science team
member Doug Ming, of the Johnson Space Center in Houston.
The soil
could be clumping together for several reasons, including the presence of salts
that bind the material together or moisture in the soil that developed during
landing and cemented the particles together. "We aren't sure what's
actually causing this," Boynton said.
Mission controllers commanded the spacecraft
to use the vibrator attached to TEGA to try to loosen the soil clumps and get
the sample into the oven. However, the first try only caused a few particles to
fall in, not enough to take a measurement, though the soil
did move.
"You
can see that the soil has actually moved, but it hasn't moved very far,"
Boynton said.
The
clumpiness of the soil combined with the large amount of dirt delivered to the
instrument seems to be keeping the sample from getting in, which Boynton noted
was interesting because scientists were worried about having too little soil,
not too much.
Scientists
will try once more to use the vibrator to get the sample into the oven, but
"we're not too optimistic that that's going to be effective," Boynton
said.
Mission scientists have worked out another
option though, which they call "sprinkling."
Phoenix has
already scooped up a second sample, and mission controllers will use this to
conduct a "sprinkle test," first over the "dumping zone"
next to the lander and then over the Microscopy, Electrochemistry and
Conductivity Analyzer (MECA) aboard the spacecraft. They will lower the scoop
at the end of the robotic arm until it is almost level, then power up the arm's
rasp (intended to scrap up samples of water ice) to vibrate the scoop and
hopefully knock out the larger clumps of the Martian regolith. They will then
try to tip out a small portion of the sample onto MECA.
"We
really are much better off with small amounts of soil," Boynton said.
If images
show that the sprinkle test was successful, controllers will have Phoenix dribble some of the sample into its optical microscope on Wednesday.
If the
technique works for the microscope, they'll try it on TEGA. "If we dribble
it on slowly, we'll be able to vibrate it through the screen," Boynton
said.
Mission controllers were also able to
confirm that a spring
they photographed on the ground of the landing site came from the
spacecraft, specifically from a cable on the biobarrier, which protected the
robotic arm on its 422-million mile (679-million km) journey from Earth to
Mars.
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