(CN) --- The numerous, abundant bodies of water that once dotted Mars’ surface billions of years ago have vanished but scientists believe the desert world is storing up to 99% of its water in the planet’s crust, according to a NASA-funded study released Tuesday.
The red planet’s ancient water system once held enough water to cover Mars entirely in an ocean as deep as 4,900 feet in some sections. But the system dried up more than 3 billion years ago, according to NASA.
The evidence that the fourth planet from the sun once supported massive bodies of water stems from previous NASA missions to Mars to examine geological samples.
Popular scientific theories have long held that Mars’ vast water system had evaporated beyond the planet’s atmosphere --- a process known as atmospheric escape --- due to its low gravity levels.
The NASA-funded study sought to challenge that theory by analyzing the amount of water in the forms of liquid, vapor and ice held in geological samples representing Mars’ crust across a vast timeline.
Researchers worked to define the chemical makeup of Mars’ atmosphere and crust and focused primarily on determining the ratio of deuterium --- a denser form of hydrogen --- to hydrogen in the crust.
Large quantities of deuterium would be left behind in mineral deposits if massive amounts of Mars’ water, along with its lighter-weight hydrogen, did in fact vanish through atmospheric escape, researchers theorized.
Researchers said their analysis showed few deposits of deuterium, which would be glaring evidence that any massive amount of water loss through atmospheric escape was to blame.
“Atmospheric escape doesn’t fully explain the data that we have for how much water actually once existed on Mars,” lead author and California Institute of Technology researcher Eva Scheller said in a statement released with the study.
The findings estimate that anywhere between 30% and 99% of Mars’ water is held in its crust, according to the study published Tuesday in the journal Science.
Michael Meyer, lead scientist for NASA’s Mars Exploration Program, said in the statement the trapping of water in minerals on Mars is different from Earth’s process, where water is recycled through tectonic and volcanic cycles.
Unlike Earth, Mars has no tectonic plates. So water molecules become permanently lodged in the crust.
“The hydrated materials on our own planet are being continually recycled through plate tectonics,” Meyer said. “Because we have measurements from multiple spacecraft, we can see that Mars doesn’t recycle, and so water is now locked up in the crust or been lost to space.”
The study was presented at this week’s Lunar and Planetary Science Conference by Scheller and colleagues.
Researchers did not immediately respond to a request for further comment on the study.
Last month, NASA executed its long-awaited landing of the Perseverance rover in Mars’ Jezero Crater.
The six-wheeled, SUV-sized rover will use its high-tech robotic arm and drill to collect soil and rock samples from what scientists believe was once a flourishing river delta and lake.
NASA scientists have said the 28-mile-wide crater once hosted a Lake Tahoe-sized body of water that may have left behind clues of single-celled organisms and microbial life that could’ve populated the planet.
The Perseverance rover isn’t alone in the desert world. NASA’s 1-ton, nuclear-powered Curiosity rover has been crawling across the interior of Mars’ Gale Crater since 2012.
Along with capturing stunning images of the Martian surface, Curiosity is probing geological sites for complex microbes and evidence that life-sustaining conditions once existed there.
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