New NASA Probe To 'Listen' to Mars
By MATTHEW FORDAHL
AP Science Writer

PASADENA, Calif. (AP) _ A NASA spacecraft set to land on Mars next month will attempt for the first time to capture the sounds of the Red Planet _ using a $15 microphone connected to a chip commonly found in talking toys and telephones. Unlike other instruments aboard the $165 million Mars Polar Lander, the Mars Microphone is privately funded and has no clearly defined scientific mission. Its purpose is simply to capture the planet's noises, whether they be the whoosh of a dust devil, the crackle of lightning or the whir of sand blowing through the thin atmosphere. Dead silence is another possibility. Sponsors believe the 10-second sound bites it can record will further fuel the public's interest in an alien world that for years has been fodder for science fiction _ and serve as a tool to teach the physics of sound. ``This is going to be another way of getting another sense on Mars _ and a sense of Mars,'' said Louis Friedman, executive director of the Planetary Society, a private group that spent less than $50,000 on the entire microphone project. The microphone is the culmination of a quarter century of dreams, rejections, dismissal by some scientists and clever planning. Carl Sagan, the late planetary scientist who successfully fought for cameras on spacecraft in the 1960s, first proposed wiring a lander for sound during the Viking missions to Mars in the 1970s. But the idea never became a priority because scientists believed other instruments such as thermometers and spectral analyzers could provide more valuable data. ``With our knowledge of what you get out of listening to sound, how important is that relative to other measurements?'' said Joseph Boyce, the lander's program scientist at NASA. ``It's probably important, but not as important as temperature or pressure.'' Two proposals to wire wind-measurement experiments for sound were rejected for the lander mission. Friedman thought there might be another way. After raising money from the group's 100,000 members, the society approached the Russian Space Research Institute, which was placing that nation's first instrument aboard the Mars Polar Lander. It turned out that Russia's Light Detection and Ranging device, which will study the makeup of Martian dust, had leftover space, power and communications resources, leaving room for the microphone. The Russians agreed to host it for free. Meanwhile, the Planetary Society partnered with scientists at the University of California, Berkeley's Space Science Lab to construct and test the equipment. ``Because the instrument was not built within the NASA framework, extra costs were bypassed,'' said Janet Luhmann of the Berkeley lab. The instrument consists of off-the-shelf parts, including a computer sound chip commonly found in toys and a hearing-aid microphone half the size of a pea. The whole unit is the size of pack of Post-it notes and weighs less than 2 ounces. ``When we presented that to NASA, it was an offer they couldn't refuse because it wouldn't cost them anything, it was privately funded and was for educational purposes,'' he said. About five hours after landing on Dec. 3, the microphone will record the sounds from the deployment of the lander's camera. On subsequent days, it will try to capture the noises of the planet itself with the spacecraft kept quiet. ``We sense there will be a lot of noises to listen to,'' Friedman said. ``And what they will allow us to discover we're not sure yet.'' The device is programmed to record 10 seconds at a time, with louder sounds erasing the previous recording. The quality will be equivalent to a telephone call. It can be improved, but only by reducing the recording time. After the sounds are collected and transmitted, they will be posted on the Planetary Society's Web site and played at the group's PlanetFest '99 convention on the weekend of the landing. A previous attempt to record noise from another planet never reached such an audience. Soviet scientists are believed to have placed a microphone on a Venus spacecraft in the Venera program, but results were never published. The latest microphone may sound like an expensive PR stunt, but the sounds could help both scientists and mission engineers. ``Almost anything that you put on a spacecraft that has a sensor on it, scientists will use for science,'' Boyce said. ``The microphone is going to be no exception to that. Some enterprising scientist will come up with many ways we haven't thought of to use it.''