For the first time, scientists have caught a key driver of the ongoing erosion of the atmosphere of Mars in action.
It took more than nine years’ worth of satellite data, but a team led by planetary scientist Shannon Curry of the University of Colorado Boulder has finally detected unmistakable signs of atmospheric sputtering.
This is, the researchers say, a crucial piece of the puzzle of how Mars lost both its atmosphere and its water.
Atmospheric sputtering is thought to be one of the dominant mechanisms for atmospheric loss in the early Solar System, when the Sun was brighter and more active.
It requires simultaneous observation of the flung neutral atoms, and either the ions that smacked into the atmosphere, or the electric field that accelerated them.
For the first time, researchers have observed a major factor contributing to the continuous deterioration of Mars’ atmosphere in action.
A team led by planetary scientist Shannon Curry of the University of Colorado Boulder has finally found clear evidence of atmospheric sputtering after more than nine years of satellite data.
According to the researchers, this is an essential component in understanding how Mars lost its water and atmosphere.
The team states in their paper that “these results provide a substantial step toward observationally establishing sputtering’s role in the loss of Mars’ atmosphere in order to determine the history of water and those implications for habitability over time.”. “.
When the Sun was brighter and more active in the early Solar System, atmospheric sputtering is believed to have been one of the main mechanisms for atmospheric loss. It occurs when the solar wind’s electric field accelerates ions into the atmosphere of a body without a global magnetic field, such as Mars.
The impact is similar to that of a meteorite striking a planet: energy is transferred to the neutral medium, which is then kicked up in a spray. Some atmospheric atoms and molecules, however, acquire sufficient energy to reach escape velocity through sputtering, and they are launched into space on a brand-new journey.
On Mars, it is challenging to observe this process. Either the ions that struck the atmosphere or the electric field that accelerated them must be observed concurrently with the flung neutral atoms. Deep into Mars’ atmosphere, it also necessitates concurrent daytime and nighttime observations.
NASA’s MAVEN spacecraft is the only one equipped and in orbit to make these observations. As a tracer for the phenomenon, the researchers meticulously examined the data gathered by the spacecraft since it entered Mars orbit in September 2014 in an attempt to detect simultaneous observations of the solar electric field and an abundance of argon, one of the sputtered particles, in the upper atmosphere.
The Viking 1 orbiter captured this image of Mars’ surface in 1976.
It appears to be something from a modern science fiction movie.
In that crater, there *is* a smiling face.
(@andrealuck . bsky . social) Processing by Andrea Luck; NASA/JPL-Caltech.
[picture or incorporate].
— March 17, 2025, 1:21 PM, Paul Byrne (@theplanetaryguy . bsky . social).
In contrast to argon densities at lower elevations, which stay constant, they discovered that above 350 kilometers (217 miles), argon densities change based on the direction of the solar wind electric field.
Active sputtering is the most likely explanation for the excess of heavy argon that results from the variation of lighter argon isotopes. Solar storm observations, whose outflows reached Mars in January 2016, lend credence to this. The evidence of sputtering became noticeably more noticeable during this period.
This shows what conditions might have been like billions of years ago, when the Sun was younger and rowdier, undergoing more frequent storm activity, in addition to confirming the team’s conclusion that argon density variations at high Martian altitudes are caused by sputtering.
According to the researchers, “a solar storm can significantly increase the sputtered yield and we find that atmospheric sputtering today is over four times higher than previous predictions.”.
Our findings demonstrate that sputtering is happening on Mars today and that it may have served as the primary means of atmospheric escape at Mars in the early Solar System eras, when solar activity and intense UV radiation were significantly higher. “.
