Particles blasting out from the sun stripped away what was once a thick, Earth-like atmosphere on Mars, leaving behind a dry and cold world inhospitable to life, researchers said in a study released on Thursday.
About 4 billion years ago when life was starting on Earth, Mars also had a dense atmosphere, which kept the planet warm and wet, according to the study in this week’s issue of the journal Science.
Over time, energised particles in the solar wind stripped off Mars’ atmosphere, leaving a thin and still-shrinking envelope of gases around the planet, measurements by one of NASA’s Mars-orbiting spacecraft show.
“The lines of evidence point to the period between about 3.7 billion years ago and 4 billion years ago as when Mars went bad,” lead researcher Bruce Jakosky with the University of Colorado in Boulder, said.
Conditions on early Mars could have supported microbes, Jakosky said, but as the thick atmosphere around the planet disappeared, “it went from a wet planet that could support life at the surface to the cold, dry planet we see today.”
The findings offer insight into why a planet that started off similar to Earth ended up so different and what conditions could make planets beyond the solar system suitable for life.