A study published Friday in the journal Science suggests that up to 50 percent of the water on Earth today may be older than the solar system itself, coming from the molecular cloud before the formation of the sun.

Researchers of the study, led by Ilsedore Cleeves and Edwin Bergin of the University of Michigan, simulated the chemistry involved in the formation of our solar system by constructing a detailed model of the process of creating water in a protoplanetary disk.

“Chemistry tells us that Earth received a contribution of water from some source that was very cold – only tens of degrees above absolute zero, while the sun being substantially hotter has erased this deuterium, or heavy water, fingerprint,” said Bergin in a recent statement.

Researchers focused on deuterium, which is a heavy form of hydrogen created in the big bang alongside hydrogen atoms. According to the statement, the scientists zeroed out the heavy water from the solar system simulation and observed if specific ratios of water – similar to ratios seen on Earth today – could be found.

“We let the chemistry evolve for a million years – the typical lifetime of a planet-forming disk – and we found that chemical processes in the disk were inefficient at making heavy water throughout the solar system,” said Cleeves. “What this implies is if the planetary disk didn’t make the water, it inherited it. Consequently, some fraction of the water in our solar system predates the sun.”

Results from the study estimate that between 30 and 50 percent of the water now on Earth may have existed prior to the birth of the sun 4.5 billion years ago.

“The implications of these findings are pretty exciting,” said Cleeves. “If water formation had been a local process that occurs in individual stellar systems, the amount of water and other important chemical ingredients necessary for the formation of life might vary from system to system. But because some of the chemically rich ices from the molecular cloud are directly inherited, young planetary systems have access to these important ingredients.”