It is just T-minus 3 days until liftoff for NASA’s 10th Mars mission. On July 30, 2020, Perseverance will hopefully join UAE’s “Hope” and China’s Tianwen-1 on their journey to the Red Planet in the current launch window.
Once landed in the planet’s Jezero crater (expected to be on February 18, 2021), the spacecraft will begin to investigate the geology of its surroundings and ultimately assess its past habitability. But the mission will carry out a whole host of other activities as well. And whilst the Martian helicopter Ingenuity (the first flying vehicle sent to another world) has garnered much attention, another project in the pipeline is waiting to be heard.
For the first time, two microphones onboard Perseverance will capture audio of the rover’s descent onto the planet and then ultimately the soundscape of Mars. Their use will be wide-ranging, from helping scientists to determine the composition of rocks by their popping sound to aiding maintenance checks on the rover’s instruments. But perhaps their greatest appeal is in getting the long-awaited answers of what Mars itself sounds like.
The journey to Martian sound hasn’t been easy. At least three attempts have been made since 1999 to send a microphone to Mars, but none have been successful. However, the microphones incorporated into Perseverance (in both its Entry, Descent and Landing system located in its body and SuperCam science instrument found on its "head") haven’t changed that much from when they were first designed for NASA’s ill-fated Mars Polar Lander in 1999 – they remain in a neat little box shape weighing around 30 grams (1 ounce).
“I have the same hopes for this mission as with the Mars Polar Lander!” Louis Friedman, the co-founder of the Planetary Society and the driving force behind the Mars Microphone, said in a statement. “Nothing has changed for me in that regard, because whenever we see the first picture, or first data from any mission, it’s always exciting. Waiting for the first sound from Mars will be equally exciting.”
Despite the popularity of the old adage “in space no one can hear you scream,” the sentiment is not strictly correct. Sound is a mechanical wave that requires a medium to travel through, therefore it is true that it cannot spread through a vacuum. However, although space is extremely empty, it is not quite a vacuum. There are still particles dotted around that can transmit sound waves, especially in denser regions around planets.
On Mars’ surface, the atmospheric pressure is small, less than 1 percent of Earth’s sea level pressure. Yet even at this pressure, acoustic signals within the frequency range of human hearing can be detected. Will we hear the whirling winds, a type of lightning within sandstorms, or something completely unexpected? Only time will tell, and there’s not long left to wait.