In recent weeks, the Sun has compacted so that the Earth is repeatedly bombarded with radiation and particles from solar plasma eruptions.
But Earth is not the only planet affected by solar storms. At only 1.5 times Earth’s distance from the Sun, Mars is also affected by the massive ejection of particles that blast through the Solar System.
The red planet’s magnetic field and atmosphere are weaker than Earth’s, so the effects of solar storms look a little different there. But such an effect has been recorded by instruments on the MAVEN orbiter, and now we can understand how this information can affect the radiation environment on Mars and future human explorers.
“This is the largest solar particle seen by MAVEN,” said University of California, Berkeley, physicist Christina Lee. “We’ve had several solar events in the last week, so we’re seeing wave after wave of particles hitting Mars.”
Caused by charged solar particles hitting the Curiosity rover’s navigation camera. (NASA/JPL-Caltech)Here on Earth, the biggest impact occurred in early May, when bursts of so-called coronal mass ejections (CMEs)—magnetic fields that erupt along with solar plasma and sometimes solar radiation—were blasted towards us.
As a result, solar particles combine with the Earth’s magnetic field and rain into the Earth’s atmosphere, creating a dazzling array of colors that can be seen in space, and their interaction with the particles creates a stunning glow.
The sunspot responsible for the shot then orbits on the far side of the sun, but our host star is not made by its moons. On May 20, there was a very massive flare on the far side of the sun, and the flare is predicted to be X12, making it one of the strongest solar flares ever seen. A CME immediately erupted, and Mars was in the firing line.
Light from the first flare washed over Mars X and gamma radiation. CME particles travel slower than the speed of light, so they arrive a little later and create an aura in the Martian atmosphere.
Currently, Mars does not have a global magnetic field like Earth. There is no practical internal activity to generate—no dynamo. On Earth, the magnetic field accelerates solar particles to the poles and rains them down into the ionosphere. Therefore, aurora activity is concentrated in high space.
Because Mars does not have a magnetic field capable of doing this, the aura there tends to be global. But there is a catch. The resulting ‘light reflection’ is in ultraviolet light, meaning we can’t see it with the naked eye.
Fortunately, we have satellites that can orbit the red planet. MAVEN captures the ultra-fast changes in the Martian atmosphere as solar particles move in and out.
Orbiters on the surface also measure the radiation flux from the flare. Earth’s atmosphere blocks the strongest light from reaching the surface, but the amount of atmosphere that surrounds Mars is less than 1 percent of Earth’s volume, giving it virtually no protection from the sun’s rays.
After the massive flare, Curiosity’s Radiation Evaluation Detector increased the radiation to 8,100 micrograms, allowing for 30 simultaneous chest X-rays and the largest magnification ever recorded by the rover. Such an increase would not be fatal, but it would also not be good for human health.
In fact, a curious black-and-white image was taken during a storm filled with “snow”—statically charged particles that interacted with the camera.
The measurements give scientists working on Mars missions key data points to understand what types of radiation environmental researchers may be exposed to, which could help them develop strategies to avoid or protect against such incidents.
“Cliffsides or lava tubes will provide additional protection for astronauts from such events. In the orbit of Mars or in deep space, the dose level will be greatly increased,” said Don Hassler, a physicist at the Southwest Research Institute.
Meanwhile, more storms are forecast as we enter the most active phase of the solar cycle. Hasler added, “I wouldn’t be surprised if this active region of the Sun continues to produce more solar storms on Earth and Mars in the coming weeks.”
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