If you think of yourself as a walking collection of molecules, you were never really born, and you never really die. The molecules that make you up were forged in stars and have been circulating throughout the universe in various forms for billions of years. But you aren’t the only cycling collection of stuff. A new paper published this week in Science says that the water on Earth is actually older than the Sun.

We tend to think of the Sun as the oldest part of our solar system. Billions of years ago, the Sun was the first thing to blink into life out of the cloud of gas and dust. What was left over eventually coalesced into the planets and moons that make up our the Solar System. That means, by extension, that everything on the planets, including things like surface water, are younger than the Sun.

But a new model of the Solar System is throwing a wrench in that idea, and it all comes down to deuterium.

Deuterium, sometimes called “heavy hydrogen,” is an isotope of hydrogen with an extra neutron. This gives the isotope a slightly different mass as well as a slightly different behavior in chemical reactions. Where dating water is concerned, the ratio of hydrogen to deuterium in water can tell scientists a lot about where and under what conditions the water was formed.

There’s more water sloshing on our neighboring planets and moons than you think. It obviously exists on Earth, but there’s also subsurface water on Jupiter’s moon Europa, Saturn’s moon Titan, and evidence of water has been found in meteorites from Mars and Moon rocks. It’s also in comets and asteroids. These small bodies are like time capsules; their compositions reflect the gas, dust, and ice environment that circled the Sun at its birth. From studying these small bodies, scientists know that interstellar ice has a high ratio of deuterium to hydrogen. It’s a hallmark of the water having been formed in extremely cold temperatures.

Some of Earth’s water came from interstellar sources, and not the original accretion cloud. (Credit: Bill Saxton, NSF/AUI/NRAO)

But the deuterium levels in water throughout the Solar System has been rising since the Sun’s formation, which seems strange because, well, the Sun makes thing warmer, not colder.

To see if the Sun could be behind the higher deuterium levels, a team of scientists lead by L. Ilsedore Cleeves built a computer model that ran through the Solar System’s formation. When they assumed that there was no deuterium added in the protoplanetary cloud of gas and dust from interstellar sources, the model’s modern levels of deuterium to hydrogen didn’t match what we see today. So the deuterium had to come from somewhere, and it had to exist before the Sun formed to explain the modern ratios.

To explain observations, team estimated that between 30 and 50 percent of the solar system’s water had to come from outside the gas and dust cloud that spawned our Solar System, making the water we drink older than the Sun.

And the implications behind this are pretty interesting. In the ongoing hunt for life off Earth, NASA’s maxim has long been “follow the water;” we need water for life on Earth so finding water elsewhere increases our chances of finding extraterrestrial life. If a substantial amount of our Solar System’s water predates our Solar System, it’s possible that interstellar ices have delivered water to lots of planets in other solar systems.

Following the water might be easier than we realize.

—

Feature image via NASA. Thanks to Meg Rosenburg for the paper.