NASA’s MAVEN spacecraft has provided the first direct evidence of atmospheric sputtering on Mars, revealing how solar wind has eroded the planet’s atmosphere over four billion years, turning a once-water-rich world into a barren desert.
This breakthrough, detailed in a May 2025 Science Advances paper, shows escape rates far higher than models predicted, reshaping understanding of Mars’s climate history.
Solar Wind’s Relentless Erosion
Heavy ions from the solar wind strike Mars’s upper atmosphere at 350-400 kilometers altitude, ejecting neutral atoms into space. Researchers liken the process to a cannonball splashing in a pool, with energy transfer propelling particles outward. Lacking a global magnetic field—lost more than four billion years ago—Mars has endured this cosmic sandblasting uninterrupted.
Nine Years of MAVEN Data Unlock the Secret
From 2014 to 2024, MAVEN’s three instruments tracked argon-40, a stable noble gas ideal for measuring loss. Observations revealed a 9.8-fold density increase at high altitudes during particle precipitation, with escape rates of 2.1×10²³ atoms per second—four times theoretical estimates. Chi-square tests confirmed these spikes with 99.21% confidence, ruling out chance.
Solar Storms Supercharge the Loss
Intense events amplify the effect. In January 2016, an interplanetary coronal mass ejection caused argon densities to surge over 100-fold. Four billion years ago, the young Sun’s greater activity likely intensified this, rapidly depleting the atmosphere and hastening Mars’s drying.
Evidence of a Wet Ancient Mars
Billions of years ago, Mars held water volumes equivalent to half the Atlantic Ocean, potentially forming Oceanus Borealis over 36% of its surface, 100-1,500 meters deep. Isotopic data shows losses exceeding six times the water in current polar caps. Rovers confirm this past: Curiosity’s mudstones in Gale Crater’s Yellowknife Bay, aged 3.5-3.8 billion years, indicate neutral pH lakes with microbial-friendly chemistry and wet-dry cycles lasting millions of years. Perseverance probes Jezero Crater’s river delta, where sediments preserve potential biosignatures from sustained flows ending in floods.
Magnetic Collapse and Geological Scars
Debate persists on timing, but meteorites suggest Mars’s dynamo lingered until 3.9 billion years ago in spots. Without shielding, solar wind directly stripped the atmosphere, dropping pressure below liquid water stability. Vast features like Valles Marineris—4,000 kilometers long, 200 kilometers wide, 7 kilometers deep—along with river valleys and basins, testify to powerful ancient waters carving the crust.
Today’s Harsh Reality and Lost Habitability
Mars now averages -81°F, with equatorial highs of 70°F plunging to -225°F at poles. Its 95% CO2 atmosphere exerts just 6-7 millibars—one percent of Earth’s—offering scant insulation and wild gradients. Habitability likely spanned from 4.45 to 3.5 billion years ago, with water present early; pressure fell critically by then, though niches may have endured to 2-3 billion years ago.
MAVEN’s Uncertain Future
The spacecraft enabling these insights lost contact on December 6, 2025, tumbling behind Mars. Solar conjunction until January 16, 2026, blocks recovery, leaving its orbit and mission in limbo.
These findings offer a cautionary model for exoplanets: even worlds with water, organics, and energy can turn uninhabitable without magnetic protection against stellar winds. Refined loss estimates will guide Mars’s atmospheric history and search for past life, while MAVEN’s fate underscores mission risks in deep space.
Sources:
“First direct observations of atmospheric sputtering at Mars.” Science Advances, May 2025.
“NASA’s MAVEN Makes First Observation of Atmospheric Sputtering at Mars.” NASA Science, May 2025.
“Mars Curiosity rover finds evidence of ancient lakes in Gale Crater.” Science Magazine, Dec 2014.
“Perseverance rover reveals an ancient delta-lake system and flood deposits at Jezero crater, Mars.” Science Magazine, Oct 2021.
“Revisiting timeline that pinpoints when Mars lost its dynamo.” Harvard Gazette, Nov 2023.
“NASA loses contact with MAVEN, Perseverance continues sample collection.” NASA Spaceflight, Dec 2025.