January 30, 2023

Scientists have revealed that the speed of sound on Mars is strangely different

Scientists have revealed that the speed of sound on Mars is strangely different

Scientists confirm the speed of sound Marsusing equipment on board the Perseverance rover to study the atmosphere of the red planet, which is very different from Earth’s.

What they’ve discovered may have some strange consequences for Martian communication in the future.

The results suggest that trying to speak in the Martian atmosphere may produce a strange effect, as high-pitched sound appears to travel faster than bass tones. Not that we’ll try, because the atmosphere of Mars is unbreathable, but it sure is fun to think about!

From a scientific perspective, the findings, announced at the 53rd Lunar and Planetary Science Conference by planetary scientist Baptiste Chade of Los Alamos National Laboratory, reveal high temperature fluctuations on Mars that require further investigation.

The speed of sound is not a universal constant. It can change, depending on the density and temperature of the medium through which it is transmitted; The denser the medium, the faster it will be.

That’s why sound travels about 343 meters (1,125 feet) per second in the atmosphere at 20 °C, but also at 1,480 meters per second in water, and 5,100 meters per second in steel.

The atmosphere of Mars is much weaker than that of the Earth, about 0.020 kg / m3compared to about 1.2 kg/m3 for the land. This alone means that the sound will propagate differently over the Red Planet.

But the layer of the atmosphere just above the surface, known as the planetary boundary layer, has added complications: During the day, the surface temperature rise generates convective thrusts that create powerful turbulence.

Conventional instruments for testing surface thermal gradients are highly accurate, but may suffer from different interference effects. Fortunately, persistence has something unique: microphones that can allow us to Hear the voices of Marsand a laser that can make noises at perfect timing.

A SuperCam microphone is included to record acoustic pressure fluctuations from the rover’s laser-induced avalanche spectrometer as it removes rock and soil samples from the Martian surface.

NASA’s Perseverance rover on Mars. (NASA/JPL-Caltech/MSSS)

This came with an excellent benefit, as it turns out. Chide and his team measured the time between laser firing and sound hitting a SuperCam microphone at an altitude of 2.1 meters, to measure the speed of sound at the surface.

“The speed of the sound recovered by this technique is calculated over the entire acoustic propagation path, which travels from the ground to the height of the microphone,” the researchers wrote. In their conference paper.

“So, at any given wavelength, the skew is caused by changes in temperature, wind speed and direction along that path.”

The results support predictions made using what we know about the Martian atmosphere, making sure These sounds propagate through the atmosphere near the surface at a speed of approximately 240 meters per second.

However, the eccentricity of the changing acoustic landscape of Mars is something completely unfamiliar, with conditions on the surface of Mars leading to eccentricities not seen anywhere else.

“Due to the unique properties of carbon dioxide molecules at low pressures, Mars is the only terrestrial atmosphere in the solar system that experiences a change in the speed of sound in the middle of the audible frequency range (20 Hz to 20,000 Hz),” Researchers write.

At frequencies above 240 Hz, the collision-activated patterns of CO2 molecules do not have sufficient time rest, or return to its original state. The result is that sound travels at more than 10 meters per second at higher frequencies than at lower frequencies.

This could lead to what researchers call a “unique listening experience” on Mars, where higher pitched sounds reach the listener sooner than lower pitched ones.

Since any human astronauts traveling to Mars anytime soon will need to wear pressurized spacesuits with communication equipment, or live in pressurized habitat units, this is unlikely to be an immediate problem—but it may be an interesting concept for science fiction writers. tampered with.

Because the speed of sound changes due to temperature fluctuations, the team was also able to use the microphone to measure large and rapid temperature changes on Mars that other sensors have not been able to detect. This data can help fill in some of the voids on Mars’ rapidly changing boundary layer.

The team plans to continue using the SuperCam microphone data to monitor how things like daily and seasonal changes affect the speed of sound on Mars. They also plan to compare the acoustic temperature readings with readings from other instruments to try to work out large fluctuations.

You can read the conference paper On the conference website.