Radio Lab

Strange Martian phenomenon could tune out radio static on Earth for good

New data from NASA Mars satellite MAVEN sheds light on a terrestrial problem that has vexed scientists for decades.

MAVEN, NASA

Thanks to NASA’s Mars Atmosphere and Volatile EvolutioN (MAVEN) mission to Mars, you may soon never need to fiddle with the tuning dial on a car radio again.

When we listen to songs on the radio, the sound travels via radio waves that are given out by a transmitter and then received by a receiver — in the case of a car, the car's antenna is the receiver.

Radio waves travel in the form of electromagnetic radiation from one antenna to the other. The journey, however, isn't always perfect.

Sometimes, there is a sudden spike in the amount of hot gas in the upper layer of Earth's atmosphere which causes interference in radio communications. If you are tuned into a favorite station, that could result in static, or for one radio station to be replaced by another.

This phenomenon, known as sporadic E layer, is difficult to study on Earth because that part of the planet's atmosphere is hard to reach with satellites. As a result, scientists can't predict when they will occur — leaving us to fiddle with dials.

But thanks to MAVEN, a spacecraft traveling 300 million miles away from our planet, we could finally have the solution.

MAVEN detected sporadic E layer in Mars’ upper atmosphere, and scientists are hoping to be able to use the Red Planet as an off-Earth laboratory to study the phenomenon up close. Already, the data have provided new insights into the cause of radio static, which also affects communications with aircrafts and military radars.

"What we learn on Mars is directly applicable to Earth.”

The findings are detailed in a new study published Monday in the journal Nature Astronomy.

Radio jams

MAVEN discovered the unusual ripples by pure accident.

The mission was launched in November, 2013 and has been orbiting the Red planet ever since to find out how Mars lost its atmosphere and became the desolate world it is today.

Armed with tools to measure Mars’ upper atmosphere, MAVEN’s static instrument picked up on weird “wiggles” in the data.

“As she’s flying through the upper atmosphere, [the spacecraft] kept seeing these flips,” Glyn Collinson a researcher at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and lead author of the study, tells Inverse.

These flips were spikes in the concentration of plasma, or the gas that is located in the ionized atmosphere of a planet. Sporadic E layer has never been detected on any other planet before, so the researchers didn't initially realize what they were seeing.

Joseph Grebowsky, who is a co-author of the new study and member of the MAVEN team, happens to also be an expert on the sporadic E layer phenomenon on Earth — he was able to recognize it on Mars.

Here on Earth, sporadic E layers are — as the name suggests — unusual occurrences. Spikes in plasma can come out of nowhere — cutting out your favorite tune, or essential military radio communications, without warning.

But on Mars, the weird phenomenon is long-lived and constantly forming. That means it is stable enough to study in detail.

“The physics is universal,” Collinson says. “Although there are slight differences in the details, what we learn on Mars is directly applicable to Earth.”

Revealing radio waves

Aside from their unpredictability, plasma spikes occur in the Earth’s ionosphere, the upper-most region of the atmosphere. This area is too thin for aircrafts to fly through, but too thick for satellites to orbit. As a result, scientists have known about sporadic E layer events for 80 years, but have never been able to fully understand or observe it at close hand.

Mars’ ionosphere, on the other hand, is totally accessible for spacecraft, enabling scientists to directly observe the phenomenon in action for the first time.

“Sure they’re interesting on Mars, but why they’re really exciting is that we can use it to better understand this phenomenon on Earth,” Collinson says.

Already, MAVEN is revealing intriguing details of how these weird interference events work. In its initial observations, the spacecraft also discovered a "rift" —  or a mirror opposite of sporadic E layer. Just as there can be an increase of the amount of plasma in Mars' ionosphere, there can also be a depletion, where the amount of hot gas decreases.

A rift has never been observed before, Collinson says. But it makes sense for there to be an opposite of the spike, he says, since it's logical for plasma to decrease after experiencing a spike.

The team of researchers does not know whether the rifts also take place on Earth, or if they only occur on Mars. An answer may be difficult to get: They are short-lived, which means they could be over too quickly to detect.

Mars: The ideal lab

Mars is at the top of the list for space exploration missions this decade. Scientists hope to answer the ultimate question about the Red Planet: Is it capable of hosting life? NASA is sending another rover to the planet in July, paving the way for a human-led mission to Mars. NASA hopes to launch astronauts to the Red Planet in the next decade.

MAVEN has been orbiting the red planet for more than four years now, and is still discovering new and exciting things about Mars.Lockheed Martin

For now, scientists can depend on remote craft like MAVEN to help solve this rather common, disruptive phenomenon on Earth.

“For me, what’s so exciting about this is here’s something that’s super common that happens over our heads all the time,” Collinson says. “It turns out, Mars is a good place to go to help study these things.”

MAVEN can help collect further data about sporadic E layer events, but the researchers hope to send a new mission to Mars designed specifically to study this phenomenon. That will provide a clearer picture of these unusual spikes — and how they function on our own planet.

"On Earth, they come and they mess with our radio systems without any warning and then they sort of fade," Collinson says. "But on Mars, they're right there!"

Abstract: Understanding and predicting processes that perturb planetary ionospheres is of paramount importance for long-distance radio communication. Perhaps the oldest known ionospheric disturbances are ‘sporadic E layers’1: unpredictable and short-lived concentrations of plasma2, which can bounce radio signals over the horizon for thousands of kilometres3. Consequentially, local radio broadcasts can become jammed by more distant transmissions, and thus sporadic E layers are a potentially serious complication for commercial radio, aviation, shipping or the military. According to the current theory of their formation, we should also expect an equal proportion of localized ionospheric density depletions to develop. However, no such ‘sporadic E rifts’ have been detected in over 85 years of ionospheric research. In addition, despite being common at Earth, no sporadic E layers have yet been reported at other planets. Here we report the detection of sporadic E-like phenomena in the ionosphere of Mars by NASA’s Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft, providing a physical explanation for previous unexplained observations at Mars4,5,6,7. We observe enhanced-density layers that can be explained through the presence of a sporadic E-like mechanism, and we establish the existence of sporadic E rifts in nature. We find that, unlike the case at Earth, Martian sporadic E features are trapped in a near-perpetual state of dynamic formation and may form at predictable locations. Also unlike the case at Earth, Martian sporadic E features are readily accessible to satellites, and indeed MAVEN has already encountered more of the phenomena at Mars than have ever been explored in situ at Earth with suborbital rockets.
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