Direct Observation of Atmospheric Sputtering on Mars Unveiled

In a groundbreaking study published in the journal *Science Advances*, researchers have conducted the first direct observation of atmospheric sputtering on Mars, a phenomenon believed to have significantly contributed to the loss of the planet's atmosphere over billions of years. This pivotal research, led by Shannon Curry, a planetary scientist at the University of Colorado Boulder and principal investigator of NASA's Mars Atmosphere and Volatile Evolution (MAVEN) mission, reveals how high-energy ions from the Sun interact with Mars's atmosphere, leading to the escape of neutral atoms, specifically argon.

The study, which analyzed nearly a decade's worth of data from MAVEN, indicates that sputtering, while currently a minor contributor to the atmosphere's erosion, may have been the dominant mechanism in Mars's early history when its atmosphere was likely much thicker and capable of supporting liquid water. "I've been looking for this since I was a postdoc," Curry remarked, reflecting on her long journey to this discovery. The research team's findings suggest that understanding the sputtering process is essential for comprehending Mars's transition from a once-hydrated planet to the arid landscape observed today.

Mars's atmosphere, which currently exerts less than 1% of Earth's pressure, has undergone drastic changes since its formation. According to Manuel Scherf, an astrophysicist at the Space Research Institute at the Austrian Academy of Sciences, sputtering could explain how the atmospheric pressure necessary to sustain liquid water diminished over time. This is crucial because evidence of ancient river valleys and lake beds indicates that liquid water was once present on the Martian surface.

The research highlights that sputtering occurs when ions, accelerated by the Sun's electric field, collide with neutral particles in the upper atmosphere, imparting enough energy for these particles to escape Mars's gravitational field. The team found a sputtering rate of approximately 10²³ argon atoms per second, significantly lower than the current rate of photodissociation, which dominates the atmospheric escape process today.

To successfully detect sputtering, the researchers focused their observations on Mars's night side, where the Sun's influence is minimized. Janet Luhmann, a space scientist at the University of California, Berkeley, and a collaborator on the project, emphasized the importance of these observations, stating, "We have to get out of the sunlight in order to detect sputtering."

The implications of this study extend beyond mere atmospheric science; they touch upon astrobiology, as understanding atmospheric dynamics is vital for assessing the potential for life on Mars and other celestial bodies. As Curry noted, "You cannot know whether life can exist somewhere if you don’t understand the atmosphere and how it behaves."

Despite the promising discoveries, the future of the MAVEN mission hangs in the balance due to proposed budget cuts in the 2026 federal budget, which could jeopardize further exploration of Mars. Curry expressed concern, stating, "The United States right now is number one in Mars exploration. We will lose that if we cancel these assets." The research team remains hopeful that continued support for Mars exploration will provide further insights into the planet's history and atmospheric processes, shaping our understanding of Martian evolution and the potential for past life on the Red Planet.

This study not only marks a significant achievement in planetary science but also serves as a reminder of the importance of continued investment in space exploration, as it has far-reaching implications for our understanding of planetary atmospheres and the potential for life beyond Earth.