Decagon Designs Part of the Phoenix Mars Lander

As part of the Microscopy, Electrochemistry and Conductivity Analyzer (MECA) on Nasa's Phoenix Mars Lander (launched on August 4, 2007) Decagon Devices developed an instrument to measure physical properties of the Martian regolith and atmosphere in situ. This probe, called the Thermal and Electrical Conductivity Probe (TECP), will measure regolith thermal and electrical properties, air temperature, windspeed, and atmospheric water vapor. The Phoenix Lander is equipped with a robotic arm and articulated scoop that will be used to excavate a trench in the Martian surface. TECP consists of four metal sensing needles mounted into a plastic and aluminum housing on the robotic arm, allowing TECP to probe the floor and walls of the trench.

Regolith Thermal Properties
The TECP will measure four thermal properties of the Martian regolith: temperature, thermal conductivity, volumetric heat capacity, and thermal diffusivity. This data will be used to determine how heat penetrates the Martian regolith in response to diurnal or seasonal cycles.

Regolith Electrical Properties
TECP will measure two electrical properties of the Martian regolith: electrical conductivity and dielectric permittivity. It is thought that any unfrozen water on Mars might exist in the form of thin, briny films on the surface of regolith particles. The electrical conductivity measurement can confirm the presence of such films. The dielectric permittivity measurement will identify any bulk unfrozen water in the regolith resulting from exposure of icy soil to solar heating in the robot arm trench.

Atmospheric Measurements
The TECP probe will measure atmospheric temperature and windspeed with the hotwire anemometer technique. Atmospheric water vapor will be measured with a sensor on the TECP electronics board. The data from this sensor, and measurements of the temperature of this sensor yield the vapor pressure of the Martian atmosphere. These measurements will yield valuable information about vapor phase water transport during and after excavation of the trench by the robot arm.

Dr. Douglas R. Cobos, a research scientist at Decagon, is the chief engineer on the TECP project. Contact Decagon for more details on the TECP.

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