Look: Helicopters on Mars could glow in the dark for a surprise reason

It's electrifying.

Mars Rover Perseverance and Ingenuity drone exploring the red planet. Some elements of this image fu...

Mars, a desert wasteland? It could hide some surprisingly beautiful visuals.

On Tuesday, NASA explained in a blog post how the Red Planet’s atmosphere could cause the air around a drone’s wings to glow a blueish-purple color. This is due to the drone’s blades generating an electric field.

“The faint glow would be most visible during evening hours when the background sky is darker,” William Farrell of NASA’s Goddard Space Flight Center said in a statement. Farrell and his team published their findings in the Planetary Space Journal in March 2021.

The findings demonstrate how the mysterious planet could hold more natural beauty than assumed. Images captured by NASA rovers like Perseverance show a harsh desert landscape. But the new research shows that looks can be deceiving — and Mars could impress its visitors with spectacular light shows.

View the artist’s concept of the effect below:

An artist's impression of how a drone's wings could glow in the Mars atmosphere.


Helicopters on Mars: How they could impress visitors

The effect is similar to one seen on Earth, dubbed Saint Elmo’s Fire. Encyclopedia Britannica explains that this is typically seen on the edges of wings and propellers, as these extremities brush through and discharge atmospheric electricity. It’s normally seen as a faint light, and it makes a cracking noise.

Farrell’s team found that on Mars, the drone blades would spin and touch dust grains in the atmosphere. The charge would gradually transfer onto the blades and start to create an electric field. The atmosphere would begin to conduct electricity, also known as an atmospheric breakdown.

The process is similar to that seen when rubbing a balloon over hair. This is known as triboelectric charging, and it can create a large electric field on objects.

Because the Mars atmosphere is so thin, this atmospheric breakdown is more likely to occur. That’s because the lower pressure gives the electrons more space to accelerate before they hit another molecule. Where on Earth this breakdown occurs at a relatively high three million volts per meter, this lower bar on Mars means an atmospheric breakdown can take place at only around 30,000 volts per meter.

Ingenuity made history in April 2021, when the four-pound helicopter hosted the first powered, controlled flight on another planet. Unfortunately, NASA might have to wait until a future helicopter mission before it can see whether its theory about glowing drones holds up in reality.

“Future drones could be cleared for evening flight and look for this glow,” Farrell said in a statement.

Abstract — Any rotorcraft on Mars will fly in a low-pressure and dusty environment. It is well known that helicopters on Earth become highly charged due, in part, to triboelectric effects when flying in sandy conditions. We consider the possibility that the Mars Helicopter Scout (MHS), called Ingenuity, flying at Mars as part of the Mars 2020 Perseverance mission, will also become charged due to grain-rotor triboelectric interactions. Given the low Martian atmospheric pressure of ∼5 Torr, the tribocharge on the blade could become intense enough to stimulate gas breakdown near the surface of the rotorcraft. We modeled the grain–blade interaction as a line of current that forms along the blade edge in the region where grain–blade contacts are the greatest. This current then spreads throughout the connected quasi-conductive regions of the rotorcraft. Charge builds up on the craft, and the dissipative pathway to remove charge is back into the atmosphere. We find that for blade tribocharging currents that form in an ambient atmospheric dust load, system current balance and charge dissipation can be accomplished via the nominal atmospheric conductive currents. However, at takeoff and landing, the rotorcraft could be in a rotor-created particulate cloud, leading to local atmospheric electrical breakdown near the rotorcraft. We especially note that the atmospheric currents in the breakdown are not large enough to create any hazard to Ingenuity itself, but Ingenuity operations can be considered a unique experiment that provides a test of the electrical properties of the Martian near-surface atmosphere.
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