GRIFFIN, Ga.  Tim Williams' goal was to create a device to test soil moisture around peanut pods, but his modest invention is now helping probe the soil of the Red Planet for traces of water. Williams was on sabbatical in 1987 working with a Washington State University team led by soil scientist Gaylon Campbell when he started to design a device to measure the water content around delicate peanut pods without destroying them. RELATED ARTICLE: Mars lander probes first microscope sample His handheld contraption has two parallel needles — one is heated with a known quantity of energy and the other measures what happens to that heat when it's put into the ground. The tool was uncomplicated. Most of the University of Georgia agronomist's half-dozen or so inventions are simplifications of more complex measuring instruments. Williams also designed a device to measure radiation in crops to help scientists understand the productivity of a crop and he devised a gauge of leaf coverage on the ground to estimate how much light penetrates ground cover. He'd forgotten the peanut invention until he got a call last year saying it would be part of NASA's Phoenix Mars Lander. Campbell's company, Decagon Devices, had updated the contraption for the Mars mission, making it more durable and adding the capacity to measure the thermal and electrical properties, air temperature, wind speed and water vapor. It is mounted on a robotic arm that will excavate a trench in the planet's surface. For Williams, who has researched peanuts for 38 years, it's exhilarating to see his brainchild delve into the subsoil of the Red Planet. "I got much more excited when it hit Mars and survived the impact," Williams said. "It's one of those little things you look at and say, 'Wow.'" Copyright 2008 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed. Enlarge NASA/JPL-Cal Tech/University of Arizona/Texas A&M via AFP The robotic arm on NASA's Phoenix Mars Lander as delivered the first sample of dug-up soil to the spacecraft's microscope station. A device originally designed to measure the water content around delicate peanut pods without destroying them is now one of the features on the lander. Guidelines: You share in the USA TODAY community, so please keep your comments smart and civil. Don't attack other readers personally, and keep your language decent. Use the "Report Abuse" button to make a difference. You share in the USA TODAY community, so please keep your comments smart and civil. Don't attack other readers personally, and keep your language decent. Use the "Report Abuse" button to make a difference. Read more