NASA spots sputtering for first time, cracks Mars' lost atmosphere mystery

Yahoo

a day ago

Mars just gave up one of its oldest secrets — and it took a decade, a spacecraft, and a cosmic cannonball to catch it in the act.
For the first time, NASA's MAVEN mission has directly observed a process called sputtering, an elusive atmospheric escape mechanism where energetic charged particles from the solar wind slam into the Martian atmosphere, knocking atoms into space.
This violent interaction may be a key reason why Mars lost its thick atmosphere and, with it, the ability to sustain liquid water on its surface.
The breakthrough marks a major milestone for MAVEN, a mission under NASA's Mars Exploration Program dedicated to uncovering how the Red Planet lost its atmosphere.
While scientists had long suspected the process played a role in the Red Planet's atmospheric erosion, they lacked concrete evidence.
'It's like doing a cannonball in a pool,' said Shannon Curry, principal investigator of MAVEN at the Laboratory for Atmospheric and Space Physics at the University of Colorado Boulder and lead author of the study in a release.
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'The cannonball, in this case, is the heavy ions crashing into the atmosphere really fast and splashing neutral atoms and molecules out.'
Previous findings—like the imbalance between lighter and heavier argon isotopes in Mars' atmosphere—offered only indirect clues, pointing to sputtering's fingerprints without capturing the act itself.
Since lighter isotopes naturally reside higher in the atmosphere, their scarcity compared to heavier ones strongly suggested they had been knocked away into space. And the only known process capable of selectively removing these lighter isotopes is sputtering.
'It is like we found the ashes from a campfire,' said Curry. 'But we wanted to see the actual fire, in this case sputtering, directly.'
Now, using data from three instruments aboard MAVEN—the Solar Wind Ion Analyzer, the Magnetometer, and the Neutral Gas and Ion Mass Spectrometer—researchers have, for the first time, captured sputtering in action.
Additionally, the team needed measurements across the dayside and the nightside of the planet at low altitudes, which takes years to observe.
By combining data from three of MAVEN's instruments, scientists created the first detailed map linking sputtered argon to incoming solar wind.
The map showed argon atoms high in the Martian atmosphere, precisely where energetic particles had slammed into it—clear, real-time evidence of sputtering in action.
Even more striking, the process was occurring at a rate four times higher than expected, with activity intensifying during solar storms. This direct observation confirms that sputtering was a major driver of atmospheric loss during Mars' early years, when the young Sun was far more active.
'These results establish sputtering's role in the loss of Mars' atmosphere and in determining the history of water on Mars,' said Curry.
The discovery helps fill a major gap in our understanding of Mars' transformation from a once-habitable planet to the cold, dry world we see today. It also provides critical insight into how planets evolve and what it might take for them to remain habitable.
The findings have been published this week in Science Advances.