A team of scientists have made a discovery that could help solve one of Earth’s greatest mysteries, where did our planet’s water come from? Using powerful radio telescopes, the researchers have detected water vapour in a comet located far beyond Neptune’s orbit, and the results are changing our understanding of how life sustaining water arrived on our world.
The comet, known as 29P/Schwassmann-Wachmann 1, orbits in the outer reaches of our Solar System between Jupiter and Neptune. What makes this discovery remarkable is that the astronomers detected water vapour so far from the Sun, where temperatures are extremely cold. This suggests the comet contains unusually volatile materials that can sublimate, transitioning directly from ice to gas, even in the frigid outer Solar System.
This Image of the Week features the remarkable Comet 29P, imaged by Gemini North of the international Gemini Observatory (Credit : International Gemini Observatory)
Using the Atacama Large Millimetre/submillimetre Array (ALMA) in Chile, scientists observed distinct radio wavelengths emitted by water molecules as they escaped from the comet’s nucleus. This marks one of the most distant detections of water vapour from a comet ever achieved, providing crucial data about the composition of these ancient remnants from our Solar System’s formation.
For decades, scientists have debated how Earth acquired its oceans with leading theories suggesting water arrived through bombardment by comets and asteroids during the planet’s early history, roughly 4 billion years ago. However, not all water sources it seems are created equal.
Two of the Atacama Large Millimeter/submillimeter Array (ALMA) 12-metre antennas gaze at the sky at the observatory’s Array Operations Site (AOS), high on the Chajnantor plateau at an altitude of 5000 metres in the Chilean Andes (Credit : Iztok Bončina/ESO)
The key lies in the ratio of heavy water (deuterium) to regular water. Different regions of the Solar System produced ice with distinct deuterium signatures. By analyzing these ratios in comets, asteroids, and Earth’s oceans, scientists can trace which celestial bodies most likely delivered our water.
Previous studies of comets from the inner Solar System showed deuterium ratios that didn’t match Earth’s oceans very well. However, comets from the outer Solar System, like 29P appear to have ratios much closer to what we find in Earth’s water. This discovery strengthens the theory that comets from the distant Kuiper Belt and Oort Cloud were major contributors to our planet’s water supply.
Known objects in the Kuiper belt beyond the orbit of Neptune. (Scale in AU. Distances but not sizes are to scale; the yellow disk is about the size of Mars’ orbit and the planets Jupiter, Saturn, Uranus and Neptune are also shown
Understanding how Earth acquired its water has implications for the search for life elsewhere. If we can determine which types of celestial bodies best deliver life sustaining water to rocky planets, we can better predict which exoplanetary systems might harbour habitable worlds.
This research demonstrates the power of modern radio astronomy to probe the chemical composition of distant objects. As telescopes become more sensitive, scientists expect to detect water vapour in even more distant comets, building a comprehensive map of water distribution throughout our Solar System’s history.
Each new detection brings us closer to understanding not just how Earth became a blue planet, but how common water rich worlds might be throughout the universe.
Source : Comet’s Water Holds Clues to Life on Earth