Sounds of Mars

01Hi, Curious Universe listeners.

02Before we get into the episode, we have a quick note for you.

03On February 18, 2021, NASA's Perseverance rover landed safely on Mars and recorded sounds from the Red Planet for the very first time.

04The interviews you're going to hear in this Sounds of Mars episode were recorded before the landing happened.

05You're going to hear about what NASA experts hoped the sounds would be like, along with the actual sound recorded on Mars.

06We hope you enjoy.

07This is NASA's Curious Universe.

08Our universe is a wild and wonderful place.

09I'm Patti Boyd, and in this podcast, NASA is your tour guide.

10Since 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.

11Perseverance is on a mission to explore Mars and collect Martian samples so we can eventually study them here on Earth.

12This isn't the first time we've sent a rover to Mars.

13There are two robots actively exploring the Red Planet already, the Curiosity rover and the InSight lander.

14But Perseverance will do something different.

15For the first time, Perseverance will collect sounds from Mars.

16Hi, this is David Gruul, 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.

17David Gruul works at JPL, NASA's Jet Propulsion Laboratory, in Pasadena, California.

18He was the Launch Operations Manager for Perseverance.

19And he recorded this interview on one of the same kinds of microphones that was sent to collect sound from Mars.

20This microphone is a DPA-4006 omnidirectional microphone.

21You 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.

22We haven't done a mission or a science instrument yet that we haven't learned something new or interesting or exciting.

23And our hope is that our off-the-shelf microphone will help us learn something new about Mars that we wouldn't know otherwise.

24Scientists expect that because Mars is so different from Earth, that sounds there would be different too.

25Mars is colder.

26The 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.

27So 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.

28Earth's atmosphere is mainly nitrogen and oxygen, with trace amounts of other gases, like carbon dioxide.

29Mars' atmosphere, though, is composed almost entirely of carbon dioxide.

30Because 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 bass and types of things like that, will come through the atmosphere better than those high noises will.

31If you were on Mars, you'd sound pretty much like yourself.

32But you would sound a little quieter, and even a little muffled.

33That's because the atmosphere of Mars is much thinner than Earth's, only about 1% as thick at the surface.

34Air density affects how well sound waves can travel.

35Since the atmosphere is less dense, the noise is likely going to be quieter.

36So it'll be harder for us to hear, you know, quiet noises, things of that nature.

37And even loud noises are going to sound a little bit softer than we would expect them to be here on Earth.

38Scientists hypothesize that sounds on Mars would be 20 decibels lower compared to what they sound like on Earth.

39NASA scientists have created an algorithm to help us imagine what common sounds from Earth would sound like on Mars.

40Let's listen to a few.

41This is the sound of an ocean on Earth.

42And here's what it might sound like on Mars.

43It may be hard to hear sounds of bells or chimes on Mars, but listen closely.

44And a conversation on Earth might sound like whispers on Mars.

45For 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.

46However, we can persevere.

47Might sound like this on Mars.

48We are a species of explorers and we will meet many setbacks on the way to Mars.

49However, we can persevere.

50Scientists can do a lot of guessing and make calculations about what sounds on Mars would be like.

51But the Mars Perseverance rover's two microphones will help us find out for sure.

52I think it's going to be real neat to actually hear sounds from another planet.

53You know, there's lots of theories and papers being written about exactly what it will sound like.

54But actually sitting back and listening to sounds from a couple hundred million miles away, you never know what you might find out.

55Before we can listen to the unique sounds of Mars, the rover first has to land safely on the planet's surface.

56The transition from flying through space to hurtling down into a planet's atmosphere is a crucial stage of the mission.

57It's known as Entry, Descent, and Landing, or EDL.

58Some of the team, like JPL's Orisa Stille, call it the seven minutes of terror.

59The 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.

60For the roughly seven minutes of its descent, the rover will not be able to communicate with NASA in real time.

61The onboard computer will have to move the mission through a perfectly choreographed set of motions without any help from mission control.

62The team goes through many tests ahead of time to prepare.

63We 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.

64Because you have to piece all of this together, there's always this fear that, you know, 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.

65And so there's a little bit of terror in waiting to see if that goes as planned, goes as you expect it to.

66On landing day, ERISA and the EDL team watch as Perseverance goes through these crucial phases and prepares to touch down on Mars.

67So it starts with us separating the cruise stage before we start entry.

68And this is before the spacecraft would start to interact with the atmosphere at Mars.

69When we start to interact with the atmosphere at Mars, we're going about 12,000 miles per hour.

70And then we'll go through the different phases of entry where we're doing what we call entry guidance.

71So 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.

72This is a truly turbulent part of the rover's trip and potentially the riskiest.

73When we deploy the parachute, we're going around Mach 1.7.

74And so it's a supersonic parachute that's going to continue to slow us down.

75The parachute has deployed and we're seeing significant deceleration.

76While we're on the parachute, we have to do a couple of things to get ready for landing.

77One of them is to release the heat shield.

78And 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.

79I like to think of the descent stage as a jet pack that's going to fly the rover down close to the surface, where that separates from the back shell and parachute.

80And then that's when we start what we call the sky crane maneuver that we use to actually lower the rover on some cables closer to the surface.

81About 20 meters off the surface.

82And at that point, we're trying to set the rover down going about 1.7 miles per hour onto the surface.

83At that point, we would call touchdown once we believe that the rover is safely on the ground.

84Touchdown confirmed.

85Perseverance safely on the surface of Mars, ready to begin seeking the sands of path life.

86And as soon as that happens, the descent stage cables are cut away and the descent stage flies off into the distance.

87And then for the first time, we're going to hear the ambient noises of Mars.

88The wind possibly blowing by.

89Things like that.

90So that's going to give us our first indication, our first sounds from the surface of Mars being captured by the microphone and then returned to the Earth soon thereafter.

91It takes time to send the sound files from Mars to Earth.

92And then even more time to process them.

93We 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 background noises that are there also.

94Here are more of the sounds of Mars from the EDL microphone after they've been processed.

95Listen closely.

96Jim Green, NASA's chief scientist, is excited about these sounds and what we'll continue to learn from them.

97As you can imagine, landing a car-sized rover on the surface of Mars is quite an event.

98But it's really just the beginning of Perseverance's journey.

99The Perseverance rover has this very long, tall mast.

100And this mast is about the size of a six-foot human.

101Imagine standing next to Perseverance and looking around, looking over the vastness of the environment.

102You would see much of the hills and the valleys.

103Perseverance is a beautiful rover, one metric ton.

104And its main job is to core rock.

105That means, with a drill, create a cylinder of rock about the size of a Crayola Cran and store it in a metal tube for later return.

106The samples are incredibly important because it tells us the history of the geology of Mars.

107What happened to the planet over time?

108You know, here on Earth, our rock record tells us a lot about the history of this planet.

109We hope to find the same on Mars with these samples.

110The samples Perseverance collects will be brought to Earth by future missions that are planned for the latter half of this decade.

111Although Perseverance's main job is to core rock, it also has a laser and another microphone.

112We also have another microphone that's connected to a fabulous instrument called SuperCam.

113This is an experiment that identifies minerals and rock composition.

114It has a laser and the laser goes out, zaps rock, and we want to hear that whole process.

115It's like snap, crackle, pop because that rock will burn, that rock will basically explode, and we want to be able to hear that.

116That tells us a lot about composition and other elements that will be necessary to interpret the observations.

117Now that the rover is safely on Mars, it can begin on the science part of its mission.

118Perseverance will send NASA key information about Mars, which could then help pave the way for future human exploration of the Red Planet.

119One thing's for certain, when it comes to Mars, we'll be learning and listening for years to come.

120Sounds captured by the EDL microphone were played in this podcast episode.

121Want to hear the full sounds?

122Visit soundclad.com slash NASA or check out mars.nasa.gov.

123If you liked this episode, check out more episodes of NASA's Curious Universe in your favorite podcast app.

124Find it and other NASA podcasts like Gravity Assist and On a Mission at nasa.gov slash podcasts.

125This is NASA's Curious Universe.

126This episode was written and produced by Leslie Mullen and Katie Atkinson.

127The Curious Universe team includes Michaela Sosby and Vicki Woodburn.

128Special thanks to DC Agle, Ja-Ree Cook, Ryland Hegey, Alana Johnson, Josh Handel, and NASA's Jet Propulsion Laboratory.

129Still curious about NASA?

130You can send us questions about this episode or a previous one and we'll try to track down the answers.

131You can email a voice recording or send a written note to nasa-curiousuniverse at mail.nasa.gov.

132Go to nasa.gov slash curiousuniverse for more information.

133NASA Jet Propulsion Laboratory, California Institute of Technology and NASA Jet Propulsion Laboratory, California Institute of Technology