Everest-sized Devil Comet might be the mysterious source of Earth’s water, say scientists

Everest-sized Devil Comet might be the mysterious source of Earth’s water, say scientists (Image: Canva)

Sometimes the biggest answers hide within the night sky. Scientists now believe Earth’s oceans may trace their beginnings to ancient comets. A new study has provided the clearest evidence yet.

Did Earth’s water really come from comets?
Researchers found that Comet 12P/Pons-Brooks contains water matching Earth’s oceans. The comet, nicknamed the “devil comet,” was studied using advanced observatories in Chile and Hawaii. Measurements showed its water vapour carried the same deuterium-to-hydrogen ratio found in our seas.

The icy body, about Mount Everest in size, swept near Earth during the April 2025 total solar eclipse. It was the comet’s first close approach since 1954. Following a 71-year orbit, it belongs to the ancient Halley-type family of comets, relics from the solar system’s birth.

How did scientists confirm the water’s origin?
By mapping both normal water and heavy water, researchers confirmed the vapour rose directly from the comet’s nucleus. This ruled out chemical processes in the surrounding coma. NASA scientist Stefanie Milam said the analysis showed gases emerging from frozen ices locked deep inside the comet’s core.

For decades, scientists argued Earth formed too hot to hold water. The leading theory suggested water arrived later through icy impacts. However, earlier comet studies failed to show a close match. The Pons-Brooks data gave one of the strongest similarities yet, said NASA astrophysicist Martin Cordiner.

What are the wider implications for space research?
This discovery supports the argument that Halley-type comets contributed to making Earth habitable. The finding also questions whether comets brought organic molecules along with water. Future missions, such as ESA's Comet Interceptor and NASA's planned CAESAR project, would be able to test these hypotheses further by bringing comet samples back to Earth.