NASA's Curious Universe - Sounds of Mars

Episode Date: February 22, 2021

On February 18, 2021, NASA’s Mars Perseverance rover completed its 300 million mile journey and landed safely on the Red Planet. Here’s what it heard. This special episode of NASA’s Curious Universe features the first-ever raw recorded sounds from Mars. Jim Green, David Gruel and Erisa Stilley explain what you're hearing.

Hi, curious universe listeners. Before we get into the episode, we have a quick note for you. On February 18, 2021, NASA's Perseverance rover landed safely on Mars and recorded sounds from the red planet for the very first time. The interviews you're going to hear in the Sounds of Mars episode were recorded before the landing happened. You're going to hear about what NASA experts hoped the sounds would be like, along with the actual sound recorded on Mars.

We hope you enjoy. This is NASA's curious universe. Our universe is a wild and wonderful place. I'm Patty Boyd, and in this podcast, NASA is your tour guide. Since the summer of 2020, a Mars rover named Perseverance has been hurtling through space, flying many thousands of miles per hour towards its final destination. The Red Planet. Perseverance is on a mission to explore Mars and collect Martian samples so we can eventually study them here on Earth.

This isn't the first time we've sent a rover to Mars. There are two robots actively exploring the red planet already, the Curiosity rover and the Insight Lander. But Perseverance will do something different. For the first time, Perseverance will collect sounds from Mars. Hi, this is David Gruel, and I am speaking to you. using one of the EDL cam microphones similar to the ones that are destined for the surface of Mars. David Grull works at JPL, NASA's Jet Propulsion Laboratory in Pasadena, California. He was the launch operations manager for Perseverance.

And he recorded this interview on one of the same kinds of microphones that was sent to collect sound from Mars. This microphone is a DPA-406 omnidirectional microphone. You could buy the exact same microphone, the exact same components off of the internet, hook them up to your computer, and that would be the exact hardware that we are using for our system. We haven't done a mission or a science instrument yet that we haven't learned something new or interesting or exciting. And our hope is that our off-the-shelf microphone will help us learn something new about Mars that we wouldn't know otherwise. Scientists expect that because Mars is so different from Earth, that sounds. there would be different too.

Mars is colder. The colder atmosphere and the type of the atmosphere means that it's got a lower speed of sound, which means that it'll take longer for the sounds to actually reach the microphone. So if you're close to the microphone, you probably won't notice a difference, but if you're farther away, it would take you a little bit longer for the sounds to get there. Earth's atmosphere is mainly nitrogen and oxygen, with trace amounts of other gases, like carbon dioxide. dioxide. Mars's atmosphere, though, is composed almost entirely of carbon dioxide. Because of all the carbon dioxide, that's likely going to cause the higher pitched frequency noises

to be attenuated, meaning that you can probably hear the lower noises, the base and types of things like that, will come through the atmosphere better than those high noises will. If you were on Mars, you'd sound pretty much like yourself. yourself. But you would sound a little quieter and even a little muffled. That's because the atmosphere of Mars is much thinner than Earth's, only about 1% as thick at the surface. Air density affects how well sound waves can travel. Since the atmosphere is less dense, the noise is likely going to be quieter. So it would be harder for us to hear, you know, quiet noises, things of that nature and even loud noises are going to sound a little bit softer than we would expect

them to be here on Earth. Scientists hypothesize that sounds on Mars would be 20 decibels lower compared to what they sound like on Earth. NASA scientists have created an algorithm to help us imagine what common sounds from Earth would sound like on Mars. Let's listen to a few. This is the sound of an ocean on Earth. And here's what it might sound like on Mars.

It may be hard to hear sounds of bells or chimes on Mars, but listen closely. And a conversation on Earth might sound like whispers on Mars. For example, this essay from Alex Mather, the student who named the rover, We are a species of explorers, and we will meet many setbacks on the way to Mars. However, we can persevere. Might sound like this on Mars. We are species of explorers, and we will meet many setbacks on the way to Mars. However, we can persevere.

Scientists can do a lot of guessing and make calculations about what sounds on Mars would be like. But the Mars Perseverance rovers' two microphones will help us find out for sure. I think it's going to be real neat to actually hear sounds from another planet. You know, there's lots of theories and papers being written about exactly what it will sound like. But actually sitting back and listening to sounds from a couple hundred, million miles away, you never know what you might find out. Before we can listen to the unique sounds of Mars, the rover first has to land safely on the planet's surface. The transition from flying through space to hurtling down into a planet's atmosphere is a

crucial stage of the mission. It's known as entry, descent, and landing, or EDL. Some of the team, like JPL's ERISA Stilly, call it the seven minutes of terror. The terror part of it, I think, comes from the fact that when we send something to another planet, because the physics of that planet are different, we can't simulate, we can't test, I should say, the full event on Earth, the way that it would need to be tested to fully mimic the conditions it's going to see at Mars. For the roughly seven minutes of its descent, the rover will not be able to communicate with NASA in real time. The onboard computer will have to move the mission through a perfectly choreographed set of motions without any help from mission control.

The team goes through many tests ahead of time to prepare. We rely pretty heavily on what we call these end-to-end Monte Carlo simulations that allow us to model the sensors, model the spacecraft, what the atmosphere on Mars looks like, what the terrain looks like, and just throw essentially a gauntlet of possible differences and see how the system performs statistically. Because you have to piece all of this together, there's always this fear that the first time the system's actually going to do what it was built to do is going to be the day it's supposed to work perfectly on Mars.

And so there's a little bit of terror in waiting to see if that goes as planned, goes as you expected it to. On landing day, ERISA and the EDL team, watched as perseverance goes through these crucial phases and prepares to touch down on Mars. So it starts with us separating the cruise stage before we start entry, and this is before the spacecraft would start to interact

with the atmosphere at Mars. When we start to interact with the atmosphere at Mars, we're going about 12,000 miles. miles per hour. And then we'll go through the different phases of entry where we're doing what we call entry guidance. So we're actually using the spacecraft to fly its way through the atmosphere, both to slow down, as well as to help target us back to the place that we want to end up on the surface.

This is a truly turbulent part of the rover's trip and potentially the riskiest. When we deploy the parachute, we're going around Mach 1.7. And so it's a supersonic parachute that's going to continue to slow us down. ...that the parachute has deployed and we're seeing significant acceleration. While we're on the parachute, we have to do a couple of things to get ready for landing. One of them is to release the heat shield. And that's so that we now can turn on our radar, which allows us to look at the ground and both get an estimate of the altitude that we're at as we're coming down.

as well as velocity, how quickly we're moving through the air. I like to think of the descent stage as a jetpack that's going to fly the rover down close to the surface, where that separates from the back shell and parachute. And then that's when we start what we call the sky crane maneuver that we used to actually lower the rover on some cables closer to the surface. About 20 meters off the surface. And at that point, we're trying to set the rover down going about 1.7 miles per hour onto the surface. At that point, we would call touchdown once we believe that the rover is safely on the ground.

Touchdown confirmed. And as soon as that happens, the descent stage cables are cut away, and the descent stage flies off into the distance. And then for the first time, we're going to hear the ambient noises of Mars. the wind possibly blowing by, things like that. So that's going to give us our first indication, our first sounds from the surface of Mars being captured by the microphone and then return to the Earth soon thereafter.

It takes time to send the sound files from Mars to Earth, and then even more time to process them. We take the sound file that comes back, and then we attempt to clean it up and filter it so that the noises we're of most interest in are easier to hear than the best. background noises that are there also. Here are more of the sounds of Mars from the EDL microphone after they've been processed.

Listen closely. Jim Green, NASA's chief scientist, is excited about these sounds and what will continue to learn from them. As you can imagine, landing a car-sized rover on the surface of Mars is quite an event. But it's really just the beginning of Perseverance's journey. The Perseverance Rover has this very long, tall mast. And this mast is about the size of a six-foot human. Imagine standing next to Perseverance and looking around. Looking over the vastness of the environment, you would see much of the hills

and the valleys. Perseverance is a beautiful rover, one metric ton. And its main job is to core rock. That means with a drill, create a cylinder of rock about the size of a creola cron and store it in a metal tube for later return. The samples are incredibly important because it tells us the history of the geology of Mars. What happened to the planet over time? You know, here on Earth, our rock record tells us a lot about the history of this planet. We hope to find the same on Mars with these samples. The samples Perseverance collects will be brought to Earth by future missions that are planned for the latter half of this decade.

Although Perseverance's main job is to core rock, it also has a laser and another microphone. We also have another microphone that's connected to a fabulous instrument called Supercam. This is an experiment that identifies, minerals and rock composition. It has a laser and the laser goes out and zaps rock and we want to hear that whole process. It's like snap, crackle, pop because that rock will burn, that rock will basically explode

and we want to be able to hear that. That tells us a lot about composition and other elements that will be necessary to interpret the observations. Now that the rover is safely on Mars, it can begin on the science part of its mission. Perseverance will send NASA key information about Mars, which could then help pave the way for future human exploration of the red planet. One thing's for certain. When it comes to Mars, we'll be learning and listening for years to come.

Sounds captured by the EDL microphone were played in this podcast episode. Want to hear the full sounds? Visit soundclad.com slash NASA or check out mars.nassau.gov. If you liked this episode, check out more episodes of NASA's Curious Universe in your favorite podcast app. Find it and other NASA podcasts like Gravity Assist

and on a mission at nassah.gov slash podcasts. This is NASA's Curious Universe. This episode was written and produced by Leslie Mullen and Katie Atkinson. The Curious Universe team includes Michaela Sosby and Vicki Woodburn. Special thanks to D.C. Ago, Jari Cook, Rylund Heggy, Alana Johnson, Josh Handel, and NASA's Jet Propulsion Laboratory. Still curious about NASA?

You can send us questions about this episode or a previous one, and we'll try to track down the answers. You can email a voice recording or send a written note to NASA-curious Universe at mail.nasa.gov. Go to nassah.gov slash curious universe for more information.