NASA's Phoenix Mars
Lander Uses Soil Probe And Swiss Scope
(10 July 2008) NASA's Phoenix Mars
Lander has touched Martian soil with a fork-like probe for the first time and
begun using a microscope that examines shapes of tiny particles by touching
them.
Phoenix's robotic arm pushed the fork-like probe's four
spikes into undisturbed soil Tuesday as a validation test of the insertion
procedure. The prongs of this thermal and electrical conductivity probe are
about 1.5 centimetres, or half an inch, long. The science team will use the
probe tool to assess how easily heat and electricity move through the soil from
one spike to another. Such measurements can provide information about frozen or
unfrozen water in the soil.
The probe sits on a "knuckle" of the
2.35-metre-long (7.7-foot-long) robotic arm. Held up in the air, it has
provided assessments of water vapour in the atmosphere several times since
Phoenix's May 25 landing on far-northern Mars. Researchers anticipate getting
the probe's first soil measurements following a second placement into the
ground, planned as part of today's Phoenix activities on Mars.
Phoenix
also has returned the first image from its atomic force microscope. This
Swiss-made microscope builds an image of the surface of a particle by sensing
it with a sharp tip at the end of a spring, all microfabricated from a sliver
of silicon. The sensor rides up and down following the contour of the surface,
providing information about the target's shape.
"The same day we first
touched a target with the thermal and electrical conductivity probe, we first
touched another target with a needle about three orders of magnitude smaller --
one of the tips of our atomic force microscope," said Michael Hecht of NASA's
Jet Propulsion Laboratory, Pasadena, Calif., lead scientist for the suite of
instruments on Phoenix that includes both the conductivity probe and the
microscopy station.
The atomic force microscope can provide details of
soil-particle shapes as small as about 100 nanometres, less than one-hundredth
the width of a human hair. This is about 20 times smaller than what can be
resolved with Phoenix's optical microscope, which has provided much
higher-magnification imaging than anything seen on Mars previously.
The
first touch of an atomic force microscope tip to a substrate on the microscopy
station's sample-presentation wheel served as a validation test. The substrate
will be used to hold soil particles in place for inspection by the microscope.
The microscope's first imaging began Wednesday and produced a calibration image
of a grooved substrate. "It's just amazing when you think that the entire area
in this image fits on an eyelash. I'm looking forward to exciting things to
come," Hecht said.
With these developments in the past two days, the
spacecraft has put to use all the capabilities of its Microscopy,
Electrochemistry and Conductivity Analyzer, or MECA, suite of instruments.
Researchers have begun analysing data this week from the second sample of soil
tested by MECA's wet chemistry laboratory.
Meanwhile, the Phoenix team
is checking for the best method to gather a sample of Martian ice to analyse
using the lander's Thermal and Evolved-Gas Analyzer, which heats samples and
identifies vapours from them. Researchers are using Phoenix's robotic arm to
clear off a patch of hard material uncovered in a shallow trench informally
called "Snow White." They plan in coming days to begin using a motorised rasp
on the back of the arm's scoop to loosen bits of the hard material, which is
expected to be rich in frozen water.
The atomic force microscope for
Phoenix was provided by a consortium led by the University of Neuchatel,
Switzerland.
The Phoenix mission is led by Peter Smith of the University
of Arizona with project management at JPL and development partnership at
Lockheed Martin, Denver. International contributions come from the Canadian
Space Agency; the University of Neuchatel; the universities of Copenhagen and
Aarhus, Denmark; Max Planck Institute, Germany; and the Finnish Meteorological
Institute.
(source: NASA Jet Propulsion Laboratory)
