Heavy water is a collective name for substances that are compounds of oxygen with heavy isotopes of hydrogen: deuterium and tritium. Heavy water was recently discovered for the first time in the protoplanetary disk around a young star.
Heavy water in a protoplanetary disk
The discovery of ancient water in the disk forming the planet indicates that some of the water contained in comets — and possibly even on Earth — is older than the disk’s star, providing groundbreaking insights into the history of water in our Solar System.
Using the Atacama Large Millimeter/submillimeter Array (ALMA), astronomers have detected doubly deuterated water (D₂O, or “heavy water”) for the first time in the disk forming a planet around the young star V883 Orionis. This means that the water in this disk, and therefore the water in the comets forming here, existed even before the star was born, traveling through space from ancient molecular clouds long before the formation of the Solar System.
“Our detection indisputably demonstrates that the water seen in this planet-forming disk must be older than the central star and formed at the earliest stages of star and planet formation,” says Margot Leemker, lead author of the paper and a graduate student in the Department of Physics at the University of Milan. “This presents a major breakthrough in understanding the journey of water through planet formation, and how this water made its way to our solar system, and possibly Earth, through similar processes.”
Long space journey of “heavy water”
Does this mean that the water in your morning cup of coffee could be older than the Sun? The chemical signature of D₂O shows that these water molecules survived the violent processes of star and planet formation, traveling billions of kilometers through space and time before ending up in planetary systems such as ours. Instead of being destroyed and reformed into a disk, most of this water has been inherited from the earliest, coldest stages of star formation, a cosmic legacy that may also be present on Earth today.
Scientists have not been sure whether most of the water in comets and planets formed in young disks such as V883 Orionis, or whether it is “pristine,” originating from ancient interstellar clouds.
The detection of heavy water using sensitive isotopic ratios (D₂O/H₂O) proves the ancient origin of water and provides the missing link between clouds, disks, comets, and finally planets. This discovery is the first direct evidence of interstellar water travel from clouds to the materials that form planetary systems — unchanged and untouched.
Water is fundamental to life and habitability. Knowledge about the origin of planetary water helps us understand the components of life in our Solar System and others. This discovery suggests that many young planets, and perhaps even worlds beyond our own system, may inherit water that is billions of years older than themselves, reminding us how deeply our existence is connected to the ancient history of the Universe.
According to phys.org
