Since the 1960s, we have launched dozens of missions to Mars,
attempting to learn more about our red neighbour.
We have discovered incredible things about the barren planet,
the most spectacular being that it once was a world rich with flowing water.
3.8 billion years ago, the now dry, toxic planet may have been as habitable as Earth.
But as time went on, dramatic changes caused the Martian seas and lakes to disappear.
Today, there is not flowing water, but instead drifting sand, moving across dry, dusty rocks,
all of which is wrapped in a thin, cold atmosphere.
We have all seen the incredible photos beamed back by the rovers and landers exploring Mars,
but now we can enjoy a second human sense, because NASA's Perseverance rover has the
capability of not only seeing the Martian environment, but also listening to it.
Perseverance carries two "off the shelf" commercial microphones. The first is built into
its body and was used during its entry, descent and landing. While the second is built into its
SuperCam, an instrument mounted to a long-necked mast that examines rock and soil with a camera,
laser and spectrometer, seeking organic compounds that could be related to past life on Mars.
By sending microphones, scientists will, for the first time be able to directly study how
sound propagates through the Martian atmosphere.
Previous attempts to send a microphone to Mars have all failed over the years, but we
have had a taste of what the surface sounds like.
Back in 2018, NASA's Insight lander picked up eerie sounds from Mars using its seismometer
sensor, which was at the time hailed as the first sound ever recorded from the red planet.
But, rather than relying on a seismometer sensor,
Perseverance can directly capture the real thing using dedicated commercial microphones.
Allowing the listener to hear the sounds of Mars, as if they were there standing
upon the red sands of the Jezero crater.
When we hear sound, what we are really experiencing is our eardrums vibrating.
That vibration comes from waves of pressure that travel to our ears from the source of the sound.
To get to our ears, the waves need something to travel through,
like air, liquid or even solids, And this would be the same on Mars. Compared to Earth, however,
the Martian atmosphere is entirely different in temperature, density and chemistry. So
if you could stand on Mars and listen to me without a helmet on, I would sound like this.
My voice would be a quieter, more muffled version of what you would
hear on Earth and you would have to wait slightly longer to hear it.
But the biggest change to audio would be to the high-pitch sounds. The noises
that we hear every day, like bird songs, whistles or bells would be almost inaudible.
This is due to the 96 percent Carbon dioxide within the red planet's atmosphere,
which absorbs the high pitch sound and leaves only the lower-pitched rumbles.
So as we listen to the best recordings Perseverance has captured so far,
remember that what you are hearing has come from another planet.
It might seem similar to sounds found here on Earth, but these are the sounds
of a world that at its closest is 33.9 million miles away, or 54.6 million kilometres away.
The first recording we will experience was captured in February 2021,
just 4 Martian days after Perseverance had landed. What you are about to hear
is the rumble of otherworldly wind blowing across the dry sands of a desert world.
Another benefit of having a microphone attached to the rover is that engineers can listen once
it has performed its tasks, allowing them to understand and possibly even diagnose problems
with the robot, much like a mechanic might listen closely to an engine to know what's wrong with it.
In this recording, we can hear Perseverance driving over a section of the Jezero crater.
It almost sounds brutal on the rover as it clunks and bangs across the relentless, rocky terrain.
One big surprise of the mission was when Perseverance heard the hum
of the Ingenuity drones rotors buzzing in the distance during its fourth flight test. Ingenuity
travelled to Mars attached to the belly of Perseverance
and was designed as a demonstration to test the first powered flight on Mars.
If you listen closely, the hum of the helicopter can be heard faintly above the sound of Martian wind.
3.8 billion years ago, this red planet was wet and possibly even habitable. Today Mars
is a barren desert world, that is, for now, at least only inhabited by robots. We may
not be able to hear the sound of flowing water across its red rocks, but what you
have just listened to is nonetheless the sound of an alien planet and a robot exploring it.