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When the sun unleashed an extreme solar storm and hit Mars in May, it engulfed the red planet with auroras and an influx of charged particles and radiation, according to NASA.
The sun has been showcasing more activity over the past year as it nears the peak of its 11-year cycle, called solar maximum, which is predicted to occur later this year.
Within recent months, there has been a spike in solar activity, such as X-class flares, the strongest of solar flares, and coronal mass ejections, or large clouds of ionized gas called plasma and magnetic fields that erupt from the sun’s outer atmosphere.
Solar storms that reached Earth in May sparked colorful auroras that danced in the skies over areas that rarely experience them, such as Northern California and Alabama.
The storms originated from a massive cluster of sunspots that happened to face Earth. Then, that sunspot cluster rotated in the direction of Earth’s cosmic neighbor: Mars.
Astronomers used the plethora of orbiters encircling the red planet, as well as rovers driving across its surface, to capture the impacts of a solar storm on Mars firsthand — and to understand better what kind of radiation levels the first astronauts on the red planet may experience in the future.
Solar radiation hits Mars
The most extreme storm occurred on May 20 after an X12 flare released from the sun, according to data collected by the Solar Orbiter spacecraft currently studying the sun.
The massive flare sent X-rays and gamma rays hurtling toward Mars, and a coronal mass ejection released quickly on the heels of the flare, flinging charged particles in the direction of the red planet.
The X-rays and gamma rays traveled at the speed of light and reached Mars first, followed by the charged particles within tens of minutes, according to scientists tracking the activity from NASA’s Moon to Mars Space Weather Analysis Office at the Goddard Space Flight Center in Greenbelt, Maryland.
The Curiosity rover, currently exploring Gale Crater just south of the Martian equator, took black-and-white images using its navigation cameras during the solar storm. White streaks resembling snow, which can be seen in the images, are the result of charged particles hitting Curiosity’s cameras, according to NASA.
The energy from the solar particles was so strong that the star camera aboard the Mars Odyssey orbiter, which helps orient the probe as it circles the planet, momentarily shut down. Fortunately, the spacecraft was able to turn the camera back on within an hour. The last time Odyssey faced such extreme solar behavior was during the solar maximum of 2003, when an X45 flare fried the orbiter’s radiation detector.
Meanwhile, Curiosity used its Radiation Assessment Detector, or RAD, to measure the amount of radiation hitting the planet during the storm. An astronaut standing next to the rover would have experienced radiation equal to 30 chest X-rays, which isn’t deadly, but is the largest such surge of radiation that the rover’s instrument has measured since landing nearly 12 years ago.
Understanding the peak radiation that astronauts may experience on the red planet helps scientists to plan how to protect those on crewed exploration to Mars in the future.
“Cliffsides or lava tubes would provide additional shielding for an astronaut from such an event. In Mars orbit or deep space, the dose rate would be significantly more,” said Don Hassler, RAD principal investigator at the Southwest Research Institute’s Solar System Science and Exploration Division in Boulder, Colorado, in a statement. “I wouldn’t be surprised if this active region on the Sun continues to erupt, meaning even more solar storms at both Earth and Mars over the coming weeks.”
Auroras on the red planet
The MAVEN orbiter, short for Mars Atmosphere and Volatile EvolutioN, had an aerial view of auroras dancing in ultraviolet light over Mars during the solar storm. The orbiter launched to Mars in 2013 to study how the red planet has lost its atmosphere over time and how space weather generated by the sun interacts with the upper Martian atmosphere.
But these auroras appear much different from the northern lights, or aurora borealis, and southern lights, or aurora australis, that occur on Earth.
When the energized particles from coronal mass ejections reach Earth’s magnetic field, they interact with gases in the atmosphere to create different colored lights in the sky, specifically near its poles.
But Mars lost its magnetic field billions of years ago, which means the planet has no shield from incoming energized solar particles. So when the particles hit Mars’ thin atmosphere, the reaction results in planet-engulfing auroras.
“Given Mars’ lack of a global magnetic field, Martian aurorae are not concentrated at the poles as they are on Earth, but instead appear as a ‘global diffuse aurora’ that are associated with Mars’ ancient, magnetized crust,” wrote Deborah Padgett, Operational Product Generation Subsystem task lead at NASA’s Jet Propulsion Laboratory in Pasadena, California, in the space agency’s Curiosity rover blog.
Future astronauts may be able to witness these Martian light shows one day, according to NASA.
By tracing the data from multiple Martian missions, scientists were able to watch how the solar storm unfolded.
“This was the largest solar energetic particle event that MAVEN has ever seen,” said MAVEN Space Weather Lead Christina Lee of the University of California, Berkeley’s Space Sciences Laboratory, in a statement. “There have been several solar events in past weeks, so we were seeing wave after wave of particles hitting Mars.”