NASA's Phoenix Mars Lander has
scooped up another sample of Martian dirt into one of its onboard laboratory
ovens. The sample will complete a profile of all depths of the surface layer of
Phoenix's
arctic landing site.
The lander's
robotic arm collected the sample, dubbed Burning
Coals, from a trench informally named Burn Alive 3. The sample comes from
an intermediate depth between the surface regolith
and the rock-hard subsurface icy layer, which Phoenix confirmed was water ice on July 31.
The $420 million Phoenix
mission is analyzing the surface material in the Martian arctic too look
for signs of potential past habitability. The mission was originally slated to
last for three months, ending at the close of August, but NASA has extended the
mission through the end of September.
Early on Thursday, mission
controllers received information from Phoenix
that confirmed that some of the Burning Coals sample had been delivered through
the doors of cell number 7 of the lander's Thermal
and Evolved-Gas Analyzer (TEGA), almost completely filling the cell. TEGA heats
up samples and then analyzes the vapors given off to determine the composition
of the surface material.
TEGA won't begin heating a sample on
its own unless it senses the oven is completely full, so the Phoenix science team will command the oven
door to close and the cell will begin heating the sample. TEGA scientists have
sent commands to manually close oven doors before.
The sample will first be heated to
relatively low temperatures, around 95 degrees Fahrenheit (35 degrees Celsius)
so that it can detect any water vapor given off by melting ice that might be in
the sample. The oven will then heat up to 257 F (125 C) to ensure that the
sample is dry. The last step of the heating process pushes the temperature up
to 1,832 F (1,000 C) so that the instrument can detect any gases given off to
help the science team determine the specific properties of the Martian dirt.
One particular signal the Phoenix team will be
looking for is that of perchlorate, a highly
oxidizing substance that is also soluble and was detected in samples delivered
to the lander's wet chemistry lab. Seeing signs
of perchlorate in TEGA would help confirm that
wet lab finding.
"We are expecting the sample to
look similar to previous samples," said William Boynton of the University of Arizona, lead scientist for TEGA.
"One of the things we'll be looking for now is an oxygen release
indicative of perchlorate."
This new sample completes a
three-level profile of the Martian dirt that also includes surface material
from a trench called Rosy Red and ice-layer material from a trench called Snow
White.
"We want to know the structure
and composition of the soil at the surface, at the ice and in-between, to help
answer questions about the movement of water -- either as vapor or liquid --
between the icy layer and the surface," said Ray Arvidson of Washington University
in St. Louis, a leader of Phoenix science team activities.
advertisement
