El Segundo student-writer Harper Dame summarizes what science has learned about Mars' atmosphere from the exploration of the Perseverance rover.
By Harper Dame
Space exploration has advanced exponentially over the years, having progressed from landing on the surface of the moon to the establishment of the International Space Station (ISS), and now to landing vehicles on Mars. NASA (National Aeronautics and Space Administration) has recently developed the Mars rover Perseverance, which initially launched on July 30, 2020 and made its descent onto the surface of Mars on February 18, 2021. Though this was not the first rover to land on Mars, there were many firsts for its achievements after launch. Not only did this rover autonomously land itself on the surface of this planet, it also has the ability to send samples of Mars’s surface back to Earth.
Perseverance is one of the most capable rovers developed by space researchers in recent years, with the ability to collect rock/dirt samples, audio, and more from the surface of Mars. Perseverance even had its own autonomously created landing procedure and the ability to both record and transmit audio samples from the surface of Mars upon its arrival. On February 19, 2021, the first audio recording was created on The Red Planet, one day after Perseverance landed. Upon listening to these recordings, scientists concluded that Mars is a fairly quiet planet. There are not many atmospheric changes, such as wind, to create sound. Furthermore, there are not any familiar sounds like living animals, cars, or other sounds considered commonplace on Earth. Researchers originally thought that the microphone may not be working due to how quiet these recordings were, influencing scientists to turn their focus to what sounds the rover itself was making.
On Earth, the speed of sound is measured at 340 meters per second, while the speed of sound on Mars is estimated to read around 240 meters per second. This was more or less expected by most scientists due to the majority (95%) of Mars’s atmosphere being carbon dioxide, while Earth’s carbon dioxide levels are around 0.04%. Since the atmosphere is approximately 100 times thinner than Earth’s, sound is 20 decibels weaker on Mars. This means that there is a greater delay in sound transmission across vast distances on the surface of the Red Planet. For example, watching a basketball hit the ground and hearing it bounce a second later is due to sound delay. This delay would be greatly increased on Mars, and the sound of the ball hitting the ground would hypothetically be heard more than a few seconds after the initial impact.
What is even more astonishing is that there are two speeds of sound on Mars. One speed of sound is reserved for high-pitched frequencies and the other is for lower sounds. The readings on the audio recordings were read at both 20 Hz (hertz) and 20 kHz (kilohertz) on the human audible spectrum. Initially, researchers thought there may have been an issue with the microphone, as they believed it impossible to read two different speeds of sound; however, when taking into account the different types of atmosphere, two different audio transmission frequencies is quite logical. On Earth, due to a more consistent atmospheric structure, both high and low frequencies of sound travel at the same speed.
An example of differing sound frequencies here on Earth can be observed in a symphony orchestra. On Mars, sound transmission from the lower string and brass voices (cello, bass, tuba, euphonium, and trombone) would have a delayed audio transmission while high voices in the ensemble (flute, clarinet, violin, viola, and saxophone) have a faster audio transmission. This would make for a cannon-like sounding piece of music if the same melodies were to be played by both the upper and lower instruments in the ensemble.
Perseverance is a ground-breaking piece of technology that has traveled over 293 million miles to help scientists understand what is in outer space. This rover has collected over 50 hours of audio recordings for scientists to examine and decipher regarding The Red Planet, of which sound transmission studies allow us to gain a deeper understanding of atmospheres outside of Earth. These discoveries will not only help scientists understand atmospheric atmospheres on Mars, but also predict the difference in atmospheres on other planets.
Harper Dame is a writer for The Bay Eagle student newspaper at El Segundo High School.