Novel Sights and Sounds on Mars

 

The helicopter Ingenuity has now flown three times on Mars and has proven itself to be a dependable (for now) and potentially ground-breaking addition to Mars science.

Ingenuity, brought to Mars as part of the Perseverance rover landing, took off early Sunday morning on its third and most ambitious Martian mission yet.  The 4-pound helicopter traveled a total of 330 feet laterally, stayed aloft for 80 seconds and reached a maximum speed of about 4.5 mph, handily breaking marks set on its previous two flights.

In the video above, you can see the helicopter taking off on the bottom left, crossing the screen, and then coming back a bit later to land in the same spot.

The “flight was what we planned for, and yet it was nothing short of amazing,” said Dave Lavery, the Ingenuity program executive at NASA Headquarters. “With this flight, we are demonstrating critical capabilities that will enable the addition of an aerial dimension to future Mars missions.”

If this capacity proves to be robust it will clearly have many positive implications for Mars science with successor rotorcraft — allowing scientists to quickly study areas surrounding a rover and to put their discoveries into larger geological contexts.

The Mastcam-Z imager aboard NASA’s Perseverance Mars rover, which is parked at “Van Zyl Overlook” and serving as a communications base station, captured video of Ingenuity.

The Ingenuity team has been pushing the helicopter’s limits by adding instructions to capture more photos of its own – including from the color camera, which captured its first images on the second flight. As with everything else about these flights, the additional steps are meant to provide insights that could be used by future aerial missions.

On Earth, NASA sought to simulate those conditions in NASA’s Jet Propulsion Lab vacuum chambers, which were filled with wispy air consisting primarily of carbon dioxide.  But they didn’t have room for even a tiny helicopter to move more than about 1.6 feet. That posed a challenge: Would the camera track the ground as designed while moving at higher speed on Mars ?

Lots of things had to go just right for the camera to do that, said Gerik Kubiak, a JPL software engineer. Aside from focusing on the algorithm that tracks surface features, the team needs the correct image exposures because dust can obscure the images and interfere with camera performance. And the software must perform consistently.

So far, it has all worked as planned and hoped.

The Mars Helicopter is a NASA technology demonstration – a narrowly focused project that seeks to test a new capability for the first time. Previous technology demonstrations include the first Mars rover Sojourner (1997) and the Mars Cube One (MarCO) CubeSats (2018) that flew by Mars.

The helicopter doesn’t carry science instruments and isn’t part of Perseverance’s science mission. Ingenuity’s objective is an engineering one: to demonstrate rotorcraft flight in Mars’ extremely thin atmosphere.

The challenges are many.

“Mars is hard not only when you land, but when you try to take off from it and fly around, too,” said MiMi Aung, the helicopter’s project manager at JPL. “It has significantly less gravity, but less than 1% the pressure of our atmosphere at its surface. Put those things together, and you have a vehicle that demands every input be right.”

Ingenuity will attempt up to five test flights within a 30-Martian-day (31-Earth-day) demonstration window. Some have likened its pioneering aspirations to those of the Wright brothers and their Flyer aircraft, which achieved the first powered, controlled flight on Earth.

The Perseverance rover is also the first spacecraft to bring microphones to record sounds on Mars.

As described by NASA, if you were standing on Mars, you’d hear a quieter, more muffled version of what you’d hear on Earth, and you’d wait slightly longer to hear it.  The biggest change to audio would be to high-pitch sounds, higher than most voices. Some sounds that we’re used to on Earth, like whistles, bells or bird songs, would almost be inaudible on Mars.

Here is the relentless and kind of haunting wind on Mars:

When we hear sound, what we’re 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 or liquids.

The Martian atmosphere features very different temperatures,  densities and chemistry than on Earth. These differences would have three main effects on the sound you’d hear.  First is the speed of sound.

Sounds emitted in the cold Martian atmosphere would take slightly longer to get to your ear. With an average surface temperature around -81 F.  Mars has a lower speed of sound — around 540 mph per hour compared to about 760 mph on Earth. You probably wouldn’t notice up close, but over longer distances you might.

Here are the sounds of a laser zapping a rock on Mars. The sounds of 30 impacts are heard, some slightly louder than others. Variations in the intensity of the zapping sounds will provide information on the physical structure of the targets, such as its relative hardness or the presence of weathering coatings.

The sound level you’d hear would be automatically lower on Mars. The Martian atmosphere is about 100 times less dense than on Earth — that is, there’s just a lot less of it. That affects how sound waves travel from the source to the detector, resulting in a softer signal. On Mars you’d have to be much closer to the source of a sound to hear it at the same volume as you would on Earth.

The atmosphere of Mars, made up of 96 percent carbon dioxide, would absorb a lot of higher-pitched sounds, so only lower-pitched sounds would travel long distances. This effect is known as attenuation — a weakening of the signal at certain frequencies — and it would be more noticeable the farther you were from the source.

Here is a sound that will sound oddly familiar — the rover making its bumpy way across the Martian surface.

All three sound recordings were made and produced by NASA/JPL-Caltech/LANL/CNES/CNRS/ISAE-Supaero

The sounds come via two microphones on the Perseverance.

One microphone is part of the SuperCam instrument, on top of the rover’s mast. SuperCam fires a laser at distant rock targets to help determine what they’re made of.  Variations in the sounds of that laser pop give clues to the rock hardness, mass and type. This microphone has also captured the sounds of Martian wind.

The team added an additional experimental, off-the-shelf commercial microphone to the side of the rover, to record the sounds of entry, descent, and landing. While that effort did not succeed, the microphone did survive the landing and has recorded the additional sounds of the rover on Mars.