Aurora on Mars? The Martian night sky turned green in a stunning first

Green ethereal light taking over the sky on the red planet?

It might sound like a fictitious dream, but, according to NASA, it has turned out to be true!


An aurora gently glowing in wavelengths visible to the human eye has been captured on Mars for the first time – and a robot was the only one to see it live.

On March 18, 2024, as the Perseverance rover was simply hanging about, the night sky over Jezero Crater turned a faint, luminous green. What the Perseverance rover recorded opens new ways to study Mars.

Now, Mars is known to have auroras of various kinds. However, all the others we've seen have been in invisible hues of ultraviolet. As physicist Elise Wright Knutsen of the University of Oslo explained to a science journal, "Auroras are the visible manifestations of how our Sun affects planets. The confirmation that visible auroras on Mars exist opens up new, hopefully simpler and cheaper, ways that we can study these processes."

She added, "So far, we have only reported our very first detection of this green emission, but observations of auroras can tell us a lot about how the Sun's particles are interacting with Mars's magnetosphere and upper atmosphere."


The research has been published in Science Advances.

How is Aurora formed?

Auroras, like the Northern and Southern Lights, are formed when charged particles from the sun (solar wind) interact with Earth's magnetic field and atmosphere. These particles, primarily electrons and protons, are ejected from the sun's corona and travel towards Earth. Earth's magnetic field deflects most of these particles, but some are guided towards the poles, where they collide with atmospheric gases like oxygen and nitrogen.


Now, when the particles collide with other materials, they release energy and create a glow. The color of this glow depends on various factors.


Aurora on Mars?

Every planet in the Solar System has its own type of aurora, but the auroras on Mars are particularly fascinating. Auroras occur when energetic particles from space interact with a planet's particles, usually in the atmosphere, with a magnetic field playing a key role.

Mars has a very thin atmosphere, only about 2% as dense as Earth's. Additionally, Mars has a weak and patchy magnetic field that only exists in certain areas where magnetized minerals in the crust still hold traces of the magnetic field it once had. This is different from the strong protective magnetic field that surrounds Earth.

Despite this, these localized magnetic patches can still create auroras. When the solar wind blows in the right direction, these patches can cause the Martian atmosphere to glow in ultraviolet light. Researchers studying these UV auroras, led by Knutsen, discovered that the Martian atmosphere is more complex than it appears.


Knutsen explained, "We've been observing auroras on Mars for 20 years, but all our observations have been in ultraviolet light. By looking at different wavelengths, we can use quantum mechanics to determine if a certain type of glow suggests that other colors should also be present, even if we can't see them directly. For instance, a specific ultraviolet emission at 297 nanometers indicated that green light should also be there."

Motivated by these discoveries, Knutsen and her team tried to find the green light. This was not easy. Most instruments on Mars are designed for daytime observations, not for detecting faint glows at night.

Moreover, auroras on Mars are much fainter than those on Earth. The best chance to see them is right after a major solar event, like a coronal mass ejection. This requires quick action, which Mars satellites aren't always ready for.

However, on March 15, 2024, during a coronal mass ejection, everything lined up perfectly. The Perseverance rover had the instruments needed to detect the light they wanted, and a team of scientists was prepared to take immediate action.

Days after the solar event, the researchers recorded an increase in light from the Martian night sky at a wavelength of 557.7 nanometers, which is the visible glow of ionized oxygen.


Knutsen noted that even though the green aurora on Mars is the same color as the green aurora on Earth, it looks entirely different. "On Earth, we see structured ribbons and shapes in the auroras. But on Mars, the green aurora lights up the whole sky uniformly, no matter where you are," she said.

However, even if we were on Mars, we might not see this green glow with our own eyes because our vision struggles to see colors in low light. It will be interesting to see what future Mars explorers experience when they arrive.

This was the team's fourth attempt to capture this phenomenon using Perseverance, suggesting that other factors influence whether a solar event creates a visible aurora on Mars. The team plans to continue observing to understand how auroras occur and what patterns may arise.

Knutsen expressed her excitement for future research, saying, "I'm very interested in finding out what types of solar storms create this aurora. Plus, it's just really fun to imagine the red planet glowing green!"