Newswise — On May 25, NASA's Phoenix Scout Lander reached Mars, opened a soils lab, and started looking for water. Phoenix uses a robotic scoop arm to deliver regolith samples to the suite of instruments aboard the Lander--with one exception. The thermal and electrical conductivity probe (TECP) designed by a team of research scientists at Decagon Devices, Inc. is actually mounted on the robotic arm and makes direct contact with the regolith. It measures thermal conductivity, thermal diffusivity, electrical conductivity, and dielectric permittivity of the regolith, as well as vapor pressure of the air.
Finding Water, Building Climate ModelsPhoenix uses the TECP to look for evidence of water on Mars and to determine thermal properties of the regolith for use in climate models. The data collected so far await analysis, but the numbers look intriguing and promising not just for Mars study but here on earth.
Fat Needle ChallengeLogistical challenges early on forced the Decagon team to look for flexibility in the transient heated needle technique in order to build a successful thermal properties analyzer for Mars. Phoenix's robotic arm can't insert the needles as gently as a human hand. Long, thin needles approximating an infinitely long line heat source as required by the model were likely to snap when inserted into a surface of unknown hardness. The best alternative design featured stubby, conical needles which violated the assumptions of the transient heated needle theory.
Flexibility in the TheoryDecagon's Mars team doubted whether the model could even fit time and temperature data collected with a short, conical needle. "I thought there was very little chance," says Dr. Gaylon Campbell, a team member, "but it turns out that it does." By correlating the parameters generated with standards of known thermal properties, the team was able to correct the parameters generated by long, skinny needles to fit those from short, fat needles.
Mars Ingenuity on EarthDr. Doug Cobos will present the Mars teams' methods and results in a 1:30 pm oral paper on Tuesday, 7 October, at the 2008 Joint Annual Meeting of the Geological Society of America (GSA), Soil Science Society of America (SSSA), American Society of Agronomy (ASA), Crop Science Society of America (CSSA), and Gulf Coast Association of Geological Societies (GCAGS) in Houston, Texas, USA.
He will also describe how their instrument- and theory-related discoveries benefit earthside users. "We don't use conical needles in our commercial thermal properties sensors, but the mathematical models we developed for Mars make those sensors much more accurate and effective," says Dr. Colin Campbell, another member of the team. "The Mars project has expanded both the depth of our understanding and the breadth of our perspective."
**WHEN & WHERE**
Tuesday, 7 October, 1:30 PMGeorge R. Brown Convention Center, Room 310BEView abstract: http://a-c-s.confex.com/crops/2008am/webprogram/Paper47244.html
For on-site assistance during the 2008 Joint Annual Meeting, 5-9 October, contact Christa Stratton or Sara Uttech in the Newsroom, George R. Brown Convention Center, Room 350B, +1-713-853-8329.
Before or after the meeting, contact:Bryan WackerDecagon Devices, Inc.(509) 332-2756[email protected]