This discovery was made possible by an original multidisciplinary approach combining observations from the James Webb Space Telescope and quantum physics calculations. The study was carried out as part of the PDRs4All^[1] Early Release Science (ERS) programme and led by a young researcher Marion Zannese, PhD candidate at Université Paris-Saclay.

Water is an essential ingredient for the emergence of life as we know it. On Earth, most of the water in our oceans was formed long before the birth of the Solar System, in the cold regions of interstellar space (-250°C). However, a fraction of this water could have been destroyed and re-formed at higher temperatures (100-500°C) when the Solar System was still just a disk of gas and dust orbiting our nascent Sun.

To understand this enigmatic recycling of water, astronomers pointed the JWST towards "d203-506", a planet-forming disk located in the Orion Nebula, a planetary system nursery. The intense ultraviolet radiation produced by nearby massive stars leads to the rapid destruction and reformation of water in d203-506, making it a true interstellar laboratory.

But how can the formation and destruction of molecules located more than 1,000 light-years away be observed? A collaboration with quantum dynamics experts^[2], was the key to meeting this challenge. When water (H2O) is destroyed by ultraviolet light, a hydroxyl radical (OH) is released with a fast spinning (rotational) state. This is followed by the emission of photons which travel to and are detected by the JWST. In total, it is estimated that the equivalent of a terrestrial ocean is destroyed every month in the young system d203-506.

However, it doesn’t end there. Via a similar mechanism of near-infrared photon emission, JWST reveals that hydroxyl is produced in abundance from atomic oxygen by the O+H2 reaction. Hydroxyl is a key intermediate in the formation of water, as it then reacts with H2 to form water via the OH+H2 reaction. The destruction/formation cycle is complete. Some of the water making up our oceans could indeed have undergone such a cycle.