NASA's Discoveries

In February 2021, NASA’s Perseverance Rover made its landing on Mars. Comparable in size to a car but much lighter, Perseverance is outfitted with advanced tools designed for Martian exploration. Its primary mission includes gathering rock samples and assessing the atmosphere’s potential for oxygen production.

Equipped with two microphones—one on its chassis and another on its SuperCam—the rover is capable of capturing sounds from its surroundings.

So far, the auditory landscape of Mars has proven to be hauntingly quiet. Most recordings captured by Perseverance consist of the whispering Martian winds. Given the absence of life to generate sound and the planet’s notably thinner atmosphere, this silence is unsurprising.

However, Perseverance recently recorded the whir of the Ingenuity helicopter as it took off, along with the pings from its Gaseous Dust Removal Tool, which cleans core samples post-examination.

While these sounds might go unnoticed on Earth amidst various noises, they hold immense value for scientists. The precise timing and distance of the sounds enable researchers to calculate their travel speed to the rover’s microphones.

After analyzing the data, scientists from Los Alamos National Laboratory were taken aback. They discovered that the noise from the laser traveled to the microphones at a faster rate than the helicopter’s whir, revealing a unique phenomenon where sound travels at different speeds—an occurrence never previously observed.

On Earth, sound travels at a consistent speed, though it can vary with temperature and the medium. For instance, it moves faster through water than air. In contrast, the findings from Mars indicate that different pitches travel at varying speeds.

Understanding Sound Speed on Mars

On Earth, sound typically travels at approximately 1,125 feet (346 meters) per second in warm air and around 4,856 feet (1,480 meters) per second in water. Conversely, on Mars, sound travels at a slower rate of about 787 feet (239.8 meters) per second. This reduction in speed aligns with expectations due to the planet's atmospheric differences.

What’s particularly astonishing is that higher frequency sounds travel over 32 feet (10 meters) per second faster than lower frequencies. Thus, if a symphony were played on Mars, the flutes would reach your ears before the bass or cello.

Why Sound Is Slower on Mars

As mentioned, experts anticipated that sound would propagate more slowly on Mars, primarily due to the stark differences between the atmospheres of the two planets, particularly in terms of density.

Mars’ atmosphere is extremely thin—about 100 times less dense than Earth’s. According to NASA, it consists of over 95 percent carbon dioxide and less than 1 percent oxygen. The average temperature on Mars is a frigid -80 degrees Fahrenheit (-62.2 degrees Celsius), compared to Earth’s average of around 57 degrees Fahrenheit (13.9 degrees Celsius), where the atmosphere is composed of approximately 78 percent nitrogen and 21 percent oxygen.

Sound is created by waves that vibrate and agitate air molecules. On Mars, the colder atmosphere results in slower-moving molecules, and its reduced density means fewer molecules for sound waves to interact with. Additionally, carbon dioxide molecules are heavier than those of oxygen or nitrogen, further contributing to the slower sound propagation.

When sound waves are analyzed, they dissipate more quickly on Mars, dropping off after just over 26 feet (8 meters) compared to around 213 feet (65 meters) on Earth. This phenomenon explains the slower sound travel but not the differing speeds of frequencies.

Explaining the Different Speeds

Researchers attribute this frequency discrepancy to the Planetary Boundary Layer on Mars—a six-mile (10 kilometers) layer in the atmosphere that begins at the surface and is known for thermal fluctuations. The Sun heats the Martian surface during the day, creating turbulence and drafts within this atmospheric layer.

In a separate study, scientists noted, "Due to the unique properties of the carbon dioxide molecules at low pressure, Mars is the only terrestrial planet in the solar system exhibiting a sound speed change within the audible range (20 Hertz to 20,000 Hertz)."

Above 240 Hertz, the vibrational modes of carbon dioxide molecules do not return to their original state quickly enough. The result is not only remarkable but also occurs within the frequencies that humans can hear.

The Implications of Sound on Mars

The effects of this phenomenon become more pronounced with distance from the sound source. While music might sound coherent at close range, as one moves further away, the timing of the notes would become disjointed, with higher pitches arriving first and potentially rendering lower notes inaudible.

Naturally, this difference in sound travel won't impact us directly, given that humans cannot survive on Mars without extensive protective gear. Thus, it may be a long time—if ever—before we experience this unique auditory landscape firsthand. Nevertheless, the thought is intriguing.

If humans could experience music on Mars, it would likely take on an entirely different form—possibly unrecognizable. Imagine the creativity musicians could unleash while navigating the distinct acoustics of Mars, opening up a completely new realm of musical expression.

The first video presents the fascinating concept of what music might sound like on Mars, highlighting the unique acoustic properties of the Martian environment.

The second video features the official audio of "redveil - mars," providing an artistic interpretation of how sound might resonate on the Red Planet.

This article was originally published in the author’s newsletter, Curious Life, and has been edited for Medium with the author’s permission. Katrina Paulson explores the wonders of humanity, poses unanswered questions, and shares her discoveries through her writing on Medium and in her newsletters, Curious Adventure and Curious Life. Subscribing grants access to her articles and two years of archived content, with subscription fees supporting her passion for inquiry and writing. Thank you for your readership; it is greatly appreciated.