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Wednesday, July 23, 2003 Radon, Not Radar, the Key to Water Search? Finding water is perhaps the largest task for the current wave of missions to Mars, and the search may continue into the next decade or beyond as we gain a greater understanding of the Martian environment. The ESA's MARSIS radar system on the Mars Express can search up to five kilometers underground for water -- but it misses the first 100 meters. NASA is planning on plugging the gap with a new mission in 2005, but there is an even greater issue. Radar is generally good at seeing liquid water...but when it comes to ice it becomes difficult to tell it apart from the surrounding rock. So what's the solution? A scientist in France has submitted a proposal to include a radon detector on the next Mars mission by NASA. Radon is that radioactive gas that is produced from the natural decay of uranium in the ground, as many homeowners know. Normally it gets stuck in the rock, but when ice is present it can seep up through the ground, to be detected by a very inexpensive scientific instrument. It seems nearly perfect, especially since radon should be able to travel farther in the lower atmospheric pressure on Mars. Even so, Mars has given us surprises before. We have no way of knowing if radon release from the soil works the same way on the red planet as it does in our backyard, but we don't have much to lose from trying. (More info: New Scientist) @ 19:44 EST