It’s been nearly one year since Mars rover Curiosity landed on Mars in August 2012. During that year, the rover has analyzed soil, drilled rock samples to determine whether conditions on Mars could have ever been conducive to life. Now, Curiosity has fulfilled that goal.

NASA has announced that two new studies based on Curiosity’s research have been published in the journal Science. They show that the rover has uncovered evidence that Mars has lost much of its original atmosphere. Though the current Martian atmosphere is too thin for water to remain on the planet’s surface, there is evidence to suggest that water was once abundant on the red planet.

These conclusions are based on soil samples Curiosity analyzed using its Sample Analysis at Mars (SAM) instruments. The measurements compared the amount of heavier and lighter isotopes of carbon, oxygen, and hydrogen in the Martian soil. Heavier isotopes of those elements are found in Mars’ atmosphere today, suggesting to researchers that Mars’ atmosphere was lost near its top, depleting lighter isotopes.

“Getting the same result with two very different techniques increased our confidence that there’s no unknown systematic error underlying the measurements,” said Chris Webster, lead author of one of the studies and the team lead for the SAM tunable laser spectrometer at NASA’s Jet Propulsion Laboratory (JPL). “The accuracy in these new measurements improves the basis for understanding the atmosphere’s history.”

Curiosity just passed the milestone of having driven one kilometer on Mars. The rover is currently on a months-long journey to a Martian mountain named Mount Sharp, where researchers hope multiple revealed layers of rock will provide a glimpse of how the surface of the red planet has changed.