Scientists
were finally able to deliver a soil sample to an instrument aboard NASA's
Phoenix Mars Lander, after several frustrating days of failed attempts, mission
controllers announced.
The welcome
news came on Wednesday morning, when Phoenix
beamed back the results of its activities from the previous day to scientists
on Earth.
For the
last several days, scientists had tried to dislodge the clumpy soil sitting on
top of a screen that basically feeds samples into the ovens. The soil was stuck
outside the instrument's entrance. The solution was to run a vibrator on the Thermal
and Evolved-Gas Analyzer (TEGA), which is designed to heat up the soil
samples to analyze their composition.
None of the
dislodging attempts since the soil was first delivered on Saturday had been
successful, but scientists ran
the vibrator for a seventh (and likely final) time on Tuesday night "in
the off chance we might get lucky," said TEGA co-investigator William
Boynton of the University of Arizona.
"The
dirt finally did start to flow and we actually got a full oven, so that problem
is now behind us," Boynton added. "We're hopeful that some time in
the next few days we'll close the oven and begin the analysis process."
When
Boynton announced the unexpected result to the Phoenix team, "the group
just went up into cheers," he said as he played the song "(Shake,
Shake, Shake) Shake Your Booty."
TEGA's tiny
ovens will heat the samples up to progressively higher temperatures. The first
aim is to vaporize any ice that might be in the soil, which can be detected by
the instrument mass spectrometer. At higher temperatures, other minerals may
decompose into vapors as well, particularly any that formed in a wet
environment.
"We're
looking for past interactions with water," Boynton explained.
Just why
the soil took such coaxing to get into TEGA is a mystery. The soil is unlike
anything scientists expected to encounter, said Phoenix principal investigator
Peter Smith, as it tends to clump together in little clods.
Scientists
aren't sure what in the soil is causing this clumpy behavior — it could be a
particular mineral, or, some speculate, water ice (which is thought to form
layers just underneath the surface). Part of the reason ice is proposed as
causing the clumps is that the ice could have sublimed after spending several
days out in the Martian sunshine, finally loosening the soil.
Scientists
got the news about TEGA after Phoenix was sent its commands for its next day,
so they will return to it in the coming days. Phoenix will spend its next day
on the red planet delivering a sample to its optical microscope.
After the
problems encountered with dumping the soil into TEGA, mission scientists have
devised a new method of sample delivery called "sprinkling."
They will have the lander's robotic arm tilt its scoop, pushing the soil sample
to the front. They will then switch on the scoop's rasp to vibrate and loosen
soil, causing some of it to fall out in the instrument.
"It's
kind of a salt-shaker mode if you like," Smith said. "We've practiced
this before and we know it's going to work well."
"Delivering
the soil is something we're getting better at everyday," Smith added.
The first
look at a soil sample through the microscope should come on Thursday. This
close-up look at the soil should give scientists a better idea of just what is
in the Martian regolith. Scientists back at the University of Arizona have been trying to mimic the sample in their lab, but "there's something missing
in our mixtures here, and I'm quite anxious to find out what it is," Smith
said.
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