The National Aeronautics and Space Administration (NASA) announced that Perseverance captured visible auroras on Mars for the first time. The rover photographed the light show in March of last year — just a few days after the Red Planet experienced a powerful solar storm.
NASA published the results in the journal Science. Scientists reported that a large coronal mass ejection from the Sun — a powerful cloud of charged particles — struck Mars’ patchy magnetic field, disturbed its thin atmosphere, and produced the green glow.
What else did the scientists report?
The new image wasn’t accidental, writes Live Science. The Perseverance team expected a coronal mass ejection from the Sun would likely hit Mars, so they aimed the rover’s Mastcam-Z camera at the Martian night sky hoping to catch something. Still, they did not expect to witness such a spectacle.
Previously, astronomers knew there are several types of polar auroras on Mars, and that some can cover the entire planet. But until now, these phenomena had only been seen in invisible wavelengths of the electromagnetic spectrum, mainly in ultraviolet.
Now the Perseverance team says the faint green lights the rover detected are the first polar auroras in the Solar System observed in visible wavelengths.
This is also the first time Martian auroras have been recorded directly from the planet’s surface. Until now, such observations came from orbiters, like NASA’s Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft and the UAE’s Emirates Mars Mission orbiter.
Lights on Mars
Auroras can still happen on Mars because some gas remains in its atmosphere. Astronomers had long thought polar auroras on Mars were unlikely because the atmosphere is extremely thin and the planet lacks a global magnetic field, which makes its atmosphere vulnerable to being stripped by the solar wind. But the new images show there is enough gas in the Martian atmosphere to produce colorful lights.
Analysis of the green hues showed the light came from excited oxygen molecules, which make up about 0.13 percent of Mars’ thin atmosphere. That low concentration of oxygen, combined with the high level of dust in the air, is why the aurora’s light is barely visible in the photograph.
It only became noticeable after scientists removed light from Mars’ largest moon, Phobos, in the image.
Researchers say that at night near the planet’s poles another type of green glow, called airglow, may appear. Astronauts on future Mars missions might be able to see it.
Extraterrestrial auroras
Any planet in the Solar System with an atmosphere — Venus, Jupiter, Saturn, Uranus, or Neptune — can host auroras. On many of those worlds, however, the emissions occur in invisible parts of the electromagnetic spectrum: ultraviolet, infrared, or X-rays.
Primarily, auroras are caused by a stream of charged solar particles known as the solar wind. On some planets, such as Jupiter, extremely powerful auroras are driven by other phenomena, including strong magnetic interactions.
On planets closer to the Sun — Venus, Earth, and Mars — auroras are often triggered by severe space weather, such as coronal mass ejections. Even Mercury, which has almost no atmosphere, shows X-ray emissions similar to auroras when strong solar storms strike.
Powerful solar flares have become more frequent as the Sun approaches the peak of its 11-year activity cycle, the solar maximum. During this period, solar storms grow more common and intense. To predict when coronal mass ejections from the far side of the Sun might impact Earth, scientists monitor the Sun with spacecraft.
