NASA's Phoenix Mars Lander Checking Soil Properties
Tucson, Arizona -- The arm of NASA's Phoenix Mars Lander released a handful of clumpy Martian soil onto a screened opening of a
laboratory instrument on the spacecraft Friday, but the instrument did not confirm that any of the sample passed through
the screen.
Engineers and scientists on the Phoenix team assembled at the University of Arizona are determining the best approach to
get some of that material into the instrument. Meanwhile, the team has developed commands for the spacecraft to use
cameras and the Robotic Arm on Saturday to study how strongly the soil from the top layer of the surface clings together
into clumps.
Images taken Friday show soil resting on the screen over an open sample-delivery door of Phoenix's Thermal and
Evolved-Gas Analyzer, or TEGA, an instrument for identifying some key ingredients. The screen is designed to let through
particles up to one-millimeter (0.04 inch) across while keeping out larger particles, in order to prevent clogging a
funnel pathway to a tiny oven inside. An infrared beam crossing the pathway checks whether particles are entering the
instrument and breaking the beam.
The researchers have not yet determined why none of the sample appears to have gotten past the screen, but they have
begun proposing possibilities.
"I think it's the cloddiness of the soil and not having enough fine granular material," said Ray Arvidson of Washington
University in St. Louis, the Phoenix team's science lead for Saturday and digging czar for the mission.
"In the future, we may prepare the soil by pushing down on the surface with the arm before scooping up the material to
break it up, then sprinkle a smaller amount over the door," he said.
Another strategy under consideration is to use mechanical shakers inside the TEGA instrument differently than the five
minutes of shaking that was part of the sample-receiving process on Friday. No activities for the instrument are planned
for Saturday, while the team refines plans for diagnostic tests.
Phoenix's planned activities for Saturday include horizontally extending a trench where the lander dug two practice
scoops earlier this week, and taking additional images of a small pile of soil that was scooped up and dropped onto the
surface during the second of those practice digs.
"We are hoping to learn more about the soil's physical properties at this site," Arvidson said. "It may be more cohesive
than what we have seen at earlier Mars landing sites."
The Phoenix mission is led by Peter Smith at 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, Switzerland; the universities of Copenhagen and Aarhus, Denmark; Max Planck Institute, Germany; and the
Finnish Meteorological Institute. For more about Phoenix, visit: http://www.nasa.gov/phoenix and
http://phoenix.lpl.arizona.edu.
ENDS