Mars was cooked by a recent solar storm

The sun fired a volley of radiation-drenched bursts in May. When they crashed into Earth’s magnetic bubble, the world was treated to iridescent displays of the Northern and Southern Lights. But our planet wasn’t alone in the solar firing line.

A few days after Earth’s light show, a new series of eruptions screamed from the sun. This time, on May 20, Mars was hit by a monster of a storm.

Observed from Mars, “this was the strongest solar energetic particle event we have seen to date,” he said Shannon Currythe principal investigator for NASA’s Mars Atmosphere and Volatile Evolution orbiter, or MAVEN, at the University of Colorado, Boulder.

When the barrage arrived, it triggered an aurora that bathed Mars from pole to pole in a shimmering glow. If they were standing on the Martian surface, “astronauts would be able to see these auroras,” Dr. Curry said. Based on scientific knowledge of atmospheric chemistry, she and other scientists say, observers on Mars would have seen a jade-green light show, although no color cameras on the surface have picked it up.

But it is very fortunate that there were no astronauts. Mars’ thin atmosphere and absence of a global magnetic shield left its surface showered with a dose of radiation, as recorded by NASA’s Curiosity rover equal to 30 chest x-rays —not a lethal dose, but certainly not pleasant for the human constitution.

While last month’s auroras were mesmerizing, they served as a reminder that Mars can be a dangerous, radiation-ridden place and that future astronauts should be wary. “These solar storms pack quite a punch,” said Dr. Curry.

Lava tunnels — long caverns forged by volcanic activity — could provide Martian travelers with sturdy shelter from solar storms. But because the sun’s harmful particles sometimes reach Mars within minutes, Earthlings will have to tread lightly.

In other words, if you’re a Mars astronaut, “you better stay up to date on your space weather forecasts,” said James O’Donoghuea planetary astronomer at the University of Reading in England.

When the May 20 mega-eruption occurred, it was immediately clear that it was a formidable eruption. A powerful solar flare reached Mars first, bathing it in X-rays and gamma rays. Hot on its heels was a powerful coronal mass ejection — a hailshot of charged particles from the sun. “They seemed pretty fast to me,” said Mathew Owensa space physicist at the University of Reading.

When particles from a solar burst reach humanity’s home base, they are caught in Earth’s magnetic field and spiral down into the magnetic north and south poles. There, they bounce off various gas molecules in the atmosphere, temporarily energizing them and creating bursts of myriad visible colors.

Mars lost its magnetic field eons ago when its iron-rich innards stopped churning, so May’s solar bombardment went undetected. “There’s nothing stopping these particles from plowing straight into the atmosphere,” he says Nick Schneiderthe lead scientist working on the Imaging Ultraviolet Spectrograph on MAVEN at the University of Colorado, Boulder.

Subjected to a global pummeling, auroras ignited across the planet. The MAVEN orbiter documented a thundering ultraviolet glowwhile a light green tint would have been visible on the surface as it emerged from the atmosphere agitated oxygen atoms.

Some of the robot inhabitants of Mars experienced the more unpleasant effects of the storm. Charged particles hit Curiosity’s navigation cameras and the star tracker camera for the Mars Odyssey orbiter, flooding them all with static electricity like “snow.”

Solar storms can also damage a spacecraft’s solar panels. The May maelstrom was no exception. “Everybody’s solar panels took a hit,” Dr. Curry said. She added that a single solar storm like the one on May 20 “does about the same amount of damage that we typically see in a year.”

None of the spacecraft were seriously damaged – and the scientific data they recorded was warmly received. But these orbiters may not always emerge unscathed when confronted with the sun’s wrath. “The scientific team is thrilled every time we see these events,” said Dr. Curry. “The spacecraft team, less so.”