Martian moons could get electrified, and it’s scaring NASA

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Oct 19, 2017

Supercharged moons might sound awesome—who wouldn’t want to see high-voltage moon lighting up a sci-fi movie?—until you realize what they could do to spacecraft and even humans.

Just in time for Halloween, the possibility of solar storms charging moons Phobos and Deimos is giving NASA nightmares of advanced (and expensive) electronics being messed with as well as astronauts getting literally shocked. The space agency has its sights set on Phobos as a preliminary base for Mars missions because the moon’s lack of gravity makes it ideal for landing spacecraft and manning remote-control robots for practice missions, so getting charged with hundreds of volts by a coronal mass ejection could complicate things.

Mars has already been ravaged by the sun, but being a magnetized planet has its advantages. Bodies like Phobos get slammed when our star spews plasma at around a million miles an hour, as scientist William Farrell and colleagues from NASA's Goddard Space Flight Center explain in study recently published in Advances in Space Research.

“A passing coronal mass ejection (CME) will manifest a different response at an airless body compared to a magnetized planet,” Farrell said. “Specifically, because the regolith-rich surfaces of airless bodies are directly exposed to the variations in the plasma flow, the surfaces are found to undergo anomalous surface charging during the passing of CME fast plasma events.”

The day side of Phobos initially absorbs plasma blasts, creating a void that blocks it from entering on the night side. Talking a walk on the night side would be ideal for both robots and astronauts if it wasn’t for a fierce wind loaded with ions and electrons. Electrons can zoom around obstacles at warp speed like an X-wing starfighter. Ions, which are a thousand times heavier, swerve much more slowly, which allows the electrons to rocket ahead of them. This spawns an electric field that forces those ions into the void.

Meaning both man and machine could get charged if they venture into the dark side.

Say you were an astronaut and needed to explore the shadows of Phobos. As you walked on the rocky surface, friction would transfer electrical charge from dust and rock onto your space suit, and you wouldn’t be able to get rid of it. Space dust fails at conducting electricity, so that electricity won’t return to the surface but instead cling to your suit and build up the more you wander around. Solar UV radiation and electrically conducting solar wind on the day side can de-charge you, but ion and electron densities in the void are too low for that to happen. Just imagine you come back charged and then touch a conductive piece of metal—like, leaning on the side of your spaceship.    

While the charge probably sounds scarier than it actually is for astronauts, it could be a serial killer for sensitive equipment. Scientists at Goddard are now rethinking the design of future space suits and tech so when we do send craft and humans to phobos, nothing ends up being a shock. 

(via NASA Goddard)