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    Carl Sagan’s Dream of a Martian Microphone May Finally Be Real

    Written by

    Amy Thompson


    Artist's sketch of the Mars 2020 rover. Image: NASA/JPL-Caltech

    Mars 2020, the successor to the Curiosity rover, is currently under development at NASA’s Jet Propulsion Laboratory in Pasadena, California. The robotic explorer is expected to land on the Red Planet in the next decade, and could carry with it a very special instrument: the first Mars microphone.

    For the past 50 years we’ve been exploring our closest planetary neighbor, Mars, with the help of a fleet of robotic space probes. We’ve learned that Mars was once very similar to Earth; that the harsh conditions were once more hospitable, and the barren world could have supported life. We’ve got our most convincing evidence yet that Mars may have traces of liquid water on its surface today, and we’re beginning to understand how Mars lost its atmosphere. What our trusty robotic pals cannot do, however, is tell us what Mars sounds like.

    At least, not yet.

    The late Carl Sagan, scientist and co-founder of The Planetary Society, was the first to propose the idea of a Martian microphone. In 1996, he wrote a letter to NASA, petitioning the agency to consider adding a microphone to the upcoming Mars Polar Lander. "Even if only a few minutes of Martian sounds are recorded from this first experiment,” he explained, “The public interest will be high and the opportunity for scientific exploration real."

    Sagan hoped that through the development of a microphone, the sounds of Mars would enthrall the public

    The goal of the Planetary Society is to inspire and involve the public in space exploration through advocacy, projects, and education. Sagan hoped that through the development of a microphone, the sounds of Mars would enthrall the public, garnering more public interest in space exploration. Sagan’s petition was approved, and the first Mars Microphone was born.

    Designed, constructed, and tested by the University of California Berkeley’s Space Science Lab, the Mars Microphone was launched as part of the Mars Polar Lander in 1999. Unfortunately, during its descent to the Martian surface, the lander lost contact with Earth, and was never heard from again.

    Image: S. Mauric et. al./47th Lunar and Planetary Science Conference

    However, due to huge public interest, it didn’t take long for the microphone to secure a new ride. The French space agency (CNES) wanted the microphone to fly on its 2007 Netlander mission to Mars. The mission would send four identical small landers to the Martian surface in order to study the planet’s atmosphere and interior. The agency’s plan was to redesign the microphone to fit inside the lander’s camera head. However, just three years before launch, in 2004, the mission was cancelled due to lack of funding.

    The Planetary Society did not give up. It built a second microphone to ride to Mars as part of NASA’s Phoenix Lander; however, it was never turned on.

    Due to its experience with building microphones for other worlds, the Planetary Society assisted the European Space Agency in converting data collected by acoustic sensors on Cassini’s Huygens probe—part of the Cassini mission and the first probe to land on Saturn’s largest moon Titan—into sound files we can hear. In the audio file, we can hear the sound of the wind as the probe approaches the surface. Scientists can then analyze the intensity of the echoes to learn more about the surface.

    At the upcoming 47th annual Lunar and Planetary Science Conference, members of NASA’s Mars 2020 SuperCam team will make their case for why the Mars microphone should be included as part of the rover’s instrument payload.

    As the lead author of an abstract submitted to the conference, Sylvestre Maurice explains that the addition of a microphone has major scientific as well as engineering benefits. Ears on the Red Planet will give us a second sense as well as a whole new set of data. Based on the sound recordings, scientists can better measure the wind speed and even identify passing dust devils.

    The addition of a microphone will also provide scientists and engineers with another way to monitor the rover’s systems. The microphone would be able to detect the whirr of the rover’s actuators, listen as the wheels crunch across the Martian surface, and much more, allowing engineers to pick up on any potential issues.

    But that’s not all. Maurice and his team are not just satisfied with a microphone on the rover, they also want to make sure it’s included as part of the SuperCam remote-sensing instrument. SuperCam is basically a suped-up version of Curiosity’s ChemCam that uses “remote optical measurements and laser spectroscopy to determine fine-scale mineralogy, chemistry, and atomic and molecular composition of samples encountered on Mars,” according to NASA.

    At the heart of the SuperCam is a laser called the Laser Induced Breakdown Spectroscopy or LIBS. The laser is designed to analyze rock composition by vaporizing them. By adding a microphone to this instrument, scientists argue they can measure the volume of the sound produced as the laser is hitting the rock, to then determine the mass of the rock vaporized. This will provide more information to help determine what the rocks are made of.

    Perhaps some of the most exciting results to come from this microphone are the ones we aren’t expecting. Who knows what sort of sounds this microphone will pick up? Will we be able to detect the sounds of life? "We have seen other worlds and even touched them via robotic senses," said Louis Friedman, executive director emeritus of The Planetary Society, "but the Mars Microphone will offer humanity the opportunity to listen to the sounds on the surface of an alien world."