It is announced that the Phoenix Lander will open a lab on Mars. If all goes well with the nail-biting descent and landing, Phoenix's robotic arm will swing into action, delivering samples to a suite of instruments aboard the Lander. Dr. Doug Cobos, Dr. Colin Campbell, and Dr. Gaylon S. Campbell are earth scientists - literally. All three have doctoral degrees in soil physics. The instruments they design and build measure soil on earth. They were a little surprised when the Jet Propulsion Lab called to ask if they might want to send an instrument into space.

    One instrument, mounted on the digging arm, will be able to make direct contact with the Martian soil. That instrument - four short, spiky fingers - will measure soil conductivity and electrical properties among other things. The probes and the instrument that runs them were designed and built by a team of scientists at Decagon Devices, Inc. Scientists from the Jet Propulsion Laboratory had seen KD-2 Thermal Conductivity Probe at a trade show. The JPL scientists saw lots of possibilities for the KD-2 probe on Mars.

    But the probe wasn't ready for the harsh Martian conditions, and the Decagon team was hesitant to start a Martian project. "We've always avoided government contracts in favor of doing our own product development," commented Dr. Colin Campbell, "but the JPL guys insisted that we were just the group of people they were looking for - a company that combines a knowledge of fundamental soils measurements with the ability to design and build instrumentation." In the end, the project was irresistible.

    It was tough, scientifically and logistically, to figure out how to make thermal conductivity measurements on Mars, but ultimately that was the easiest part of the project. The toughest challenges came from having to put a new instrument into an old box. The Lander is named "Phoenix" for a reason. Rising from the ashes of the failed Mars Lander program, it uses a platform that was built in 2001 and then mothballed. Decagon engineers soon discovered that everything about the probe's design had already been finalized to fit the previous instrument - and it wasn't a great fit for the new probe.

    It's been a long trip for Decagon's soil scientists, but they're looking forward to a safe landing and the chance to get their hands dirty. And KD-2 users are already reaping the benefit of the Mars project here on earth. People have measured the water content of soils and other porous materials for a very long time, and the ideas surrounding that measurement are easily understood. Water potential is a more recent concept, and, in spite of its importance, is still not well understood by many soil and plant scientists. The main component of the soil water potential, the matric or capillary potential, was first described by Edgar Buckingham almost 100 years ago. Buckingham recognized that gradients in water potential are the driving passed before significant progress was made beyond Buckingham’s experiments.