First Audio Recordings of Mars Reveals Red Planet Has Two Speeds of Sound

Sound on Earth is well studied and understood, but scientists know very little about it when it comes to other planets. The Perseverance rover was launched in the summer of 2020, with its main goal being to search for signs of ancient life. It landed on the Jezero Crater on Mars on February 18, 2021 and came equipped with two microphones.

Newly analyzed findings have determined that there are two speeds of sound on Mars, with higher pitched sounds moving through the atmosphere quicker than lower frequency sounds.

The Perseverance rover landed on Mars in 2021 equipped with two microphones as part of a larger effort to give scientists the opportunity to capture the sounds of Mars for the first time.

The red planet is, unsurprisingly, very quiet. The only sound, outside of those created by the rover and its sister craft - the small Ingenuity helicopter that arrived attached to the Perseverance - is the wind.

Scientists expected sound to travel slower on Mars than Earth because Mars has a much thinner atmosphere - 170 times thinner than Earth’s - and is made up of 95% carbon dioxide, compared to Earth’s 0.04%. This makes all sound about 20 decibels weaker than on Earth.

Ultimately, this means sound – most sound anyway – travels at 240 meters per second, compared to 340 meters per second on Earth. But Sylvestre Maurice, the scientific co-director of the SuperCam recorder on Perseverance’s mast, was perplexed when the sound made by the rover’s laser traveled at 250 meters per second, 10 meters faster than expected.

“I panicked a little, I told myself that one of the two measurements was wrong because on Earth, you only have one speed of sound.”

The sound created by Ingenuity’s helicopter rotors, a much deeper sound, traveled at the expected speed of 240 meters per second.

The French CNRS institute said in a statement that the two different speeds of sound would “make it difficult for two people standing only five meters apart to have a conversation.”

That likely would not be the case inside of an artificial habitat for humans, as those would be filled with air mimicking the atmosphere on Earth.

In Maurice’s mind, the discovery proved that the “scientific gamble” of attaching recording devices on the Perseverance paid off. Two previous attempts to record sound on Mars, in 1999 and again in 2008, failed.

It is possible that future missions to other celestial bodies, like Venus or Saturn’s moon Titan, could also include microphones.

Perseverance’s mission is not over. While its core mission is only scheduled for two years, its predecessor, the Curiosity rover, continues to operate seven years after its two year mission was accomplished.