Mars has no magnetic poles and a very thin atmosphere. Therefore, researchers assumed it was impossible for Mars to have auroras. In 2005, the first signs of auroras on Mars emerged, although they were entirely different from those on Earth. Since then, scientists have been trying to understand the phenomenon better.

"Since Mars does not have a global magnetic field like we do on Earth, the interactions between particles from the sun and the atmosphere are entirely different. There are several types of auroras on Mars that does not exist here. So far, all measurements have been in the UV spectrum, which we cannot see. Since there are auroras in the UV spectrum, we have thought that they likely also exist in several wavelengths, but we haven’t had instruments capable of measuring them," explains researcher Elise Wright Knutsen at the University of Oslo.

Auroras that are visible to us were among the primary hopes of the researchers. The Mars rover Perseverance is equipped with many different types of instruments. Two of them could capture the auroras in the visible spectrum if they actually existed.

Mars borrows a bit of the Sun’s magnetic field

"Mars is a very special planet. It has an induced magnetosphere, meaning it borrows a bit of the sun's magnetic field. In addition, it has remnants of a magnetic field that it had several billion years ago, but which is no longer active. We see that there are some places where the planet's crust is magnetized. This means we have local regions with magnetic fields. It is there that the first traces of auroras were discovered," Knutsen explains.

The auroras the researchers recently have seen, have nothing to do with these local magnetic areas. The auroras that were observed occur in connection with solar storms, just like on Earth, but cover the entire planet. This type of aurora was first discovered in 2015, but until now only a handful of measurements have been made, and all in the UV specter, Knutsen reports.

Since Knutsen began the project two years ago, her greatest dream has been to capture an image of the aurora on Mars. She explains that it was an immense effort to get this one image.

Almost every day she has monitored solar storm alerts and simulations of how the storms spread throughout the solar system. This is published by NASA every time there is a solar storm. Thus, Knutsen was able to see whether the storm would hit Mars in a way that would make it possible to capture it, and whether it was the type of solar storm that could likely produce visible auroras. There were several criteria that had to be met, thus many of the solar storms would not show any results.

"Additionally, I needed to figure out when the auroras would arrive. From the simulations, I could estimate a time. Then I had to contact those who direct operations on the rover and negotiate an observation," she explains.

She had to negotiate because there are several restrictions, and many people want to use the instruments for their research. In addition the rover may have low power when a solar storm arrives or other observations may have higher priority that day.

Knutsen also had to finely calculate settings such as shutter speed on the instruments and the angle at which they should measure the sky.

Perfect storm – on a Friday

"I received a message that a perfect storm was coming, coincidentally on a Friday evening. Fortunately, I was able to schedule the activity just before the shift ended. The observation was set to take place over the weekend, so we got the results on a Monday," Knutsen recounts.

That Monday, there was a general meeting for the center where she works.

"Just before it was my turn to present, I received a file from my colleague Tim McConnochie in the U.S. This was the fourth time we had tried to observe the aurora. Since he wrote nothing in the message, I didn’t have high hopes. When I opened the file, I immediately saw that this was what we had been waiting for. I was sitting next to my new colleagues, and tears streamed down. I couldn’t say much either, as this was classified at that time. Plus, it was my 30th birthday. It was the ultimate birthday gift from Mars," says Knutsen.

Competing to be the first

"It’s a somewhat niche research field, but it’s always exciting to have the first measurements of new things," she says.

She explains that there are other groups that have instruments capable of seeing the auroras, and some of them are attempting the same observations. Therefore, she was very eager to find out if she would be the first.

"Until quite recently, this was strictly confidential. Now I can finally talk about it. I have been a researcher for a few years now, but I have never made such a discovery, so this means a lot to me," Knutsen states.

A few weeks after they received the measurements, the actual image came. She explains that it took some time because such images require extensive processing.

"I have dreamt about this picture for two years. It feels very satisfying to see it in its entirety, even though it was taken with a camera not designed for night photography. Therefore, it is a bit blurry and has a fair amount of noise. We used long exposure, which also affects how what is observed appears in the image."

Green light on Mars

She notes that the shutter speed makes the image appear somewhat greener than it would appear to humans on Mars.

"The green color characterizes atomic oxygen in the atmosphere, but the shape is different than on Earth. On Mars, the auroras will appear like a glowing green sky," Knutsen explains.

On Earth, the light has various formations. Knutsen states that measurements of auroras in the UV spectrum indicate that the auroras are evenly distributed across the sky, but she believes that the measurements do not necessarily capture the local variations of the auroras and the variations over time.

"The picture is taken with a long exposure time. It’s hard to tell anything about variations in distribution or whether it’s actually as even as it appears. Personally, I don’t believe it is completely uniform," she says.

She mentions that she has created an animation of what she believes it actually looks like. She believes that the dynamics of the magnetic field will cause the auroras to bubble.

Hopefully future expeditions will bring better night cameras

"So far, we only have one image, but if we can take more images consecutively during the same solar storm, we might be able to say something about the magnetic field dynamics on Mars. It’s about particle transport in Mars’ vicinity. The particles come in from the sunlit side but manage to turn and hit the night side. On Earth, it’s our global magnetic field that facilitates this, but Mars doesn't have that, so we don’t know what processes are responsible for this particle transport," Knutsen concludes.

According to her, studying auroras can reveal many more things about Mars that we do not know today.

"Understanding the auroras means understanding an area of the atmosphere from a distance. The color and intensity can indicate the amount and energy of the incoming particles, but it can also be indirectly used to measure pressure, temperature, and circulation in the atmosphere, says Knutsen. I hope future Mars expeditions will carry a proper night camera," she concludes.

This article was originally written in Norwegian and has been translated by Elina Melteig with assistance from artificial intelligence.

About the Project:

The project is part of the research at the Centre for Space Sensors and Systems, at the Department of Technology Systems at the University of Oslo. The research at the center focuses on creating sensors and equipment for future explorations of space. You can read more about the research at the center on their website (in English).

The center is an active part of NASA's Mars 2020 rover mission. They designed the ground radar RIMFAX. With the help of RIMFAX, it has been possible to determine that there was once flowing water on Mars.

The Instruments on Perseverance:

The Mars rover Perseverance's mission is to determine whether there could have been life on Mars. All the instruments are specially designed for this mission. The ground radar RIMFAX was designed by researchers in Knutsen's group.

Two of the instruments can be used to capture auroras in the visible spectrum.

SuperCam: Researchers use it to measure various spectra, including visible light. The “camera” can even capture the composition of different minerals from a distance.

MastCam Z: This is used to take photos in a spectrum that we can see. The camera is mounted on a mast and has many special features.

You can read more about the rover and the onboard instruments on NASA’s websites here (in English).