If you live and die by food and beverage expiration dates, you might not want to know how old some of our drinking water is. A study finds that 30% to 50% of the water found in our taps and oceans contains molecules created more than 4.5 billion years ago—making them older than our solar system and the sun, the Los Angeles Times reports. The findings from the study, published in Science, indicate that certain water molecules contain a deuterium atom instead of a hydrogen atom (making what's called "heavy water"), which could only be created under very cold, energy-replete conditions—specific conditions that didn't exist before the Earth, sun, and solar system were formed.
Earth was actually "born dry," in an extremely hot environment, according to the Times. Scientists believe we eventually received water via comets or asteroids that crashed down on Earth's surface. Figuring out where the water in the comets and asteroids came from, however, is another story, though researchers think they've narrowed it down to two possibilities: that the heavy deuterium water was dispersed among bodies in the solar system during the "violent" process of our sun's birth, or that the heavy water originated from ice found in the gas cloud from which our sun and solar system were born. Either way, researchers say this could indicate that young planets all around the universe contain water: According to scientists, there are up to 11 billion planets outside our own system that could house liquid water and, possibly, life, notes Time. (The amount of water found on Mars surprised scientists around the world.)