Solar 'cannonballs' stripped Mars' atmosphere and caused water loss, says NASA

Solar 'cannonballs' stripped Mars' atmosphere and caused water loss, says NASA

After years of silent flight above Mars, NASA’s MAVEN spacecraft has finally revealed a piece of the planet’s missing past. New findings suggest that a process called “sputtering” may be responsible for stripping away the Martian atmosphere, changing the planet’s history forever.

The study, published on 28 May in Science Advances, uses nearly a decade of MAVEN data to directly capture this process. Scientists have long believed sputtering played a major role in Mars’ climate shift, but this is the first time it’s been seen in action.

Mars’ Atmosphere Slowly Peeled Away
Mars was once a wetter world. Scientists have long pointed to evidence like dried-up riverbeds and ancient lake basins. For that much water to exist, Mars would have needed a thicker atmosphere — one that could hold in heat and pressure.

But today, Mars is cold, dry, and barely has any air. That shift likely happened as the sun’s charged particles — known as solar wind — stripped gas from the Martian sky. The key method, scientists say, was sputtering. This happens when heavy solar ions smash into Mars’ upper atmosphere. Those hits knock lighter atoms free and fling them into space.

Dr Shannon Curry, principal investigator of MAVEN at the University of Colorado Boulder, explained the effect in simple terms. "It’s like doing a cannonball in a pool," she said. "The ions crash in, splashing neutral atoms out."

A First Look at Sputtering in Real Time
By analysing data from MAVEN’s three key instruments, the team mapped argon gas in Mars’ upper layers. Argon is ideal for this type of study. It’s heavy, doesn’t react with other gases, and shows up clearly when it’s displaced.

The team found argon levels were highest in zones where solar wind was most active. This gave researchers their first direct proof that sputtering still occurs on Mars today. The gas was also located higher than expected, offering more evidence that it was being pushed up and out.

Perhaps more surprisingly, the escape rate of argon was four times greater than scientists once thought. Solar storms made the effect even stronger, hinting that Mars may have lost its atmosphere much faster in the past — especially when the young sun was more active and fierce.

Shaping the Future by Understanding the Past
Billions of years ago, Mars likely had a magnetic shield like Earth’s. But once that field faded, its atmosphere was left defenceless. Solar wind had full access, and over time, it carved the planet’s skies away.

Curry’s team believes sputtering could have been the main reason Mars dried out. “These results establish sputtering’s role in the loss of Mars' atmosphere and in determining the history of water on Mars,” she said.

Still, researchers admit the full story will take more work. They hope to combine this data with older climate models, ancient rock samples, and isotope readings. Only then will they know if sputtering was a minor leak — or the main culprit that stripped Mars of its chance at habitability.