May 19, 2022

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New evidence suggests that the speed of sound on Mars is unconventional

New evidence suggests that the speed of sound on Mars is unconventional

A selfie taken by NASA's Perseverance spacecraft on September 10, 2021.

A selfie taken by NASA’s Perseverance spacecraft on September 10, 2021.
picture: NASA / JPL-Caltech / MSSS

Using a microphone, a laser and some innovative math, a team of scientists has measured the speed of sound on Mars, in the first scientific and another remarkable discovery made possible by NASA’s Perseverance rover.

There is a lot to love about the persistence mission, but one of my favorite aspects of the rover is that it is able to record audio. Early last year, for the first time ever, we could actually hear sounds on Mars, both natural and artificial. using file SuperCam . Microphoneitinerant registered Martian winds blow, clicks From lasers scanning rocks, and the grinding sounds made by their spinning wheels.

The perseverance microphone that would detect these sounds was not certain, Looking at the painfully thin atmosphere on the red planet. Sound needs a medium to propagate, and Mars has a tiny atmospheric pressure of 0.095 pounds per square inch (psi) At ground level, it doesn’t offer much to work with. By comparison, the Earth’s sea level atmospheric pressure is about 14.7 psi.

But they were thereUnnoticeable noise Picked up by Percy’s microphone in Jezero’s crater. With sounds clearly heard on Mars, Baptiste Shane of Los Alamos National Laboratory in Los Angeles and peers she was Capable of measuring the speed of sound on Mars. Scientists recently introduced the findings In the 53rd Planetary and Lunar Science Conferencewhich was held from March 7-11 in Texas.

The a team the crane SuperCam’s Perseverance Experiment, which blasts off rocks with a laser to study the geology of Mars and It is located at the head of the probe’s mast 6.9 feet (2.1 m) above the surface of Mars. The team took measurements from 150 laser shots taken at five different locations, while also tracking local weather conditions.

By measuring the time it took the staccato-like clicking sounds to reach the SuperCam microphone, they were able to establish the speed of sound on Mars, to a precision of plus-minus 0.51%. They found that sound on Mars travels at 787 feet per second (240 meters per second), which is significantly slower than the sound of speed on Earth at 1,115 feet per second (340 m/s).

And in an observation that matched prior predictions, the speed of sounds below 240 hertz fell to 754 feet per second (230 m/s). That doesn’t happen on Earth, as sounds within the audible bandwidth (20 Hz to 20 kHz) travel at a constant speed. The “Mars idiosyncrasy,” as the scientists call it, has to do with the “unique properties of the carbon dioxide molecules at low pressure,” which makes the Martian atmosphere the only one in the solar system to experience “a change in speed of sound right in the middle of the audible bandwidth,” as the scientists wrote. The reason for this is that sounds above 240 Hz don’t have time to relax their energy, according to the scientists.

The scientists go on to say that this acoustic effect “may induce a unique listening experience on Mars with an early arrival of high-pitched sounds compared to bass.”

Unique is right! Lots of acoustic information exists below 240 Hz, including the low end of music and the lowermost registers of the human voice (typically for males). Music on Mars would sound completely messed up (particularly with increased distance), with the middle and high frequencies reaching the listener slightly before the low frequency sounds, such as the lower registers of the bass guitar and kick drum. Add another effect of carbon dioxide, the attenuating, or dampening, of higher frequencies, and the acoustic experience gets even weirder.

As a neat aside, the technique used to measure the speed of sound can also be used to measure the local temperature. So in addition to Percy’s Mars environment dynamics analyst (MEDA), the team has a new thermometer at its disposal. Looking ahead, Chide and his colleagues will conduct more tests to measure the speed of sound at different times of the day and during different Martian seasons.

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