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What colors paint Mars’ northern lights? New results from NASA’s MAVEN mission

New results from NASA’s MAVEN mission to Mars reveal colorful auroras that stretch across most of the planet’s northern hemisphere. Scientists say the auroras were so wide-reaching they could potentially cover the entire planet and be visible during daytime.

The Mars Atmosphere and Volatile Evolution, or MAVEN spacecraft, which arrived at Mars in September 2014, has made new insights into how the Martian atmosphere is ripped free from the planet during solar storms. The findings provide hints into the early evolution of Mars and may answer why the planet, which likely once hosted an ocean, is now a desolate void. They also highlight the value of a planet’s magnetic field toward sustaining life.

The press conference accompanies a set of research papers published today in Science Magazine and Geophysical Research Letters, including one on the presence of auroras or northern lights on the red planet.

“The theory is Mars has lost 99 percent of its atmosphere over many billions of years and maybe an ocean along with it,” said University of Colorado astrophysicist Nick Schneider, who led the investigation into the Mars’ auroras. “The goal of MAVEN mission is to quantify how much atmosphere can solar activity can strip away.”

Mars’ northern lights don’t just paint a colorful picture of Earth’s neighbor; they tell a story of what’s required to sustain life among billions of worlds in the galaxy.


Solar Wind Strips Martian Atmosphere. According to NASA, MAVEN measurements indicate that the solar wind strips away atmospheric gases at a rate of about 100 grams (equivalent to roughly 1/4 pound) every second. Video by NASA

Schneider and his colleagues spotted the swell of auroras last Christmas among the data being beamed by MAVEN back to Earth.

“Around last Christmas everyone had gone home to be with their families, and I thought that everybody would take a break. Then an email chain started saying, ‘Have you looked at this new data?’ It turns out for five days we saw this unexpected aurora all over Mars’ northern hemisphere, which was the only place where we were looking at the time,” Schneider said. “Everybody was in that ‘season of light’ kind of spirit, and it just showed up on our computer screens coming from Mars.”

To understand how auroras work, look no further than the fluorescent light bulbs in your office or home. Electrons accelerated by your power outlet collide with gases inside the tube, which emit light. Most gases emit at ultraviolet light, Schneider said, which is why fluorescent light bulbs use neon gas and mercury gas to get visible wavelengths. On Mars, as is the case for most of nature, gases tend to emit ultraviolet light, so the researchers relied upon MAVEN’s UV detectors to spot the auroras.

“But it turns out that our atmosphere and the Mars atmosphere both give rise to light emissions at visible wavelengths that the human eye can see. On Earth, the different colors of the aurora are indicative of whether it’s striking oxygen or nitrogen in our atmosphere,”

On Mars, Schneider says, the aurora would include reds, greens and blues due to the planet’s atmosphere being filled with carbon dioxide and related gases.

MAVEN and Mars. Illustration by NASA

MAVEN and Mars. Illustration by NASA

However, the electricity or energy needed to generate an aurora doesn’t come from a power socket. The source is high-energy particles released by our sun during a solar storm. The energetic particles slam into the gases within an atmosphere, A powerful solar storm struck Mars last December, which allowed Maven to spot these yuletide auroras.

Another essential ingredient of auroras is the strength of a planet’s magnetic field. And an ancient shift in Mars’ magnetic field may explain how the planet became desolate and mostly a dry void. The prevailing theory is that Mars has lost 99 percent of its atmosphere over many billions of years and its ocean too.

“Mars doesn’t have a global magnetic field like Earth. Most of its magnetic field disappeared billions of years ago when the interior cooled off,” Schneider said. “Without a global magnetic field, the planet’s atmospheric particles are stripped away by the sun and solar storms.”

The aurora is a visible manifestation of this conflict between solar particles intermingling with a planet’s atmosphere.

Mars lacks an internally generated global magnetic field, due to the cooling of its core. Fields surrounding Mars are a combination of small structures locked in the crust billions of years ago (lower right) and solar wind field lines draped around the planet. Photo and caption by Schneider et al., Science, 2015.

Mars lacks an internally generated global magnetic field,
due to the cooling of its core. Fields surrounding Mars are a combination of small structures locked in the crust billions of years ago (lower right) and solar wind field lines draped around the planet. Photo and caption by Schneider et al., Science, 2015.

That’s the great thing about Earth’s magnetic field. It’s so strong that we’re well protected from our atmosphere becoming dust in the wind. This strength also restricts the auroras to Earth’s north and south poles, where the magnetic field is relatively weaker.

Given the weak magnetic strength on Mars, the auroras might look like nothing seen on Earth. The team is currently analysing data to see if the spectacle happens on the southern hemisphere too. Maven recorded diffuse auroras spread over much of the northern hemisphere at night, but it was probably happening on the day side as well, Schneider said. These auroras also extended closer to the Martian surface — just 40 miles up — compared to the northern lights on Earth (60 miles up).

“You might think that’s because Mars has a lot less atmosphere, but the real difference is the energy of these solar particles,” Schneider said. “They were about 1,000 times more energetic than the particles that cause Earth’s aurora or your flourescent light bulb to glow.”

So opposed to the ribbony and swirls seen on Earth, Schneider expects that solar storms create intricate structures that shimmer or layer in waves on Mars.

The truth is that we won’t really know until astronauts land on Mars with a camera. However, these auroras are a warning sign that solar radiation is extremely intense.

This study isn’t the first to find auroras on Mars. That discovery came 10 years ago thanks to the European Space Agency’s Mars Express orbiter.

“Mars does have small leftover magnetic fields from billions of years ago, where the global magnetic field was locked in place as lava flows cooled — mostly in the Southern Hemisphere. The orbiter saw the aurora around these areas, which are known as magnetospheric umbrellas, because the field perches above the surface. That gave an indication, but it was on such a small scale, Schneider said.

When I asked Schneider why the public is so enraptured by auroras, he said:

I think that the splendor of planet wide aurora is mind boggling. All of us are explorers, and we love to be fascinated and mystified. It’s a visual connection that unites us. We can see the universe and its phenomena. Thanks to the space program, thanks to lab experiments and thanks to all of this collective effort, we can make sense of it.

Today’s news follows NASA’s discovery, reported in September, of evidence for flowing, liquid water on present-day Mars. For more, check out the press conference that NASA held earlier today:

Editor’s note: This story was updated from its original version

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