Scientists have discovered a possible “missing link” in the search for the origin of water on Earth, with evidence suggesting the planet's water could be older than the Sun, research published on Wednesday showed.
The team used ground-based telescopes to work out the chemical composition of a young star, V883 Orionis, and detected chemical signatures of heavy water in its rotating disc of gas and dust.
Lead author John J Tobin said the work suggests V883 Orionis, 1,300 light-years away from Earth, may be the connection scientists have been waiting for to understand more about how the solar system and Earth got their water.
Mr Tobin, an astronomer at the US National Radio Astronomy Observatory, said: “We can now trace the origins of water in our solar system to before the formation of the Sun.
“The composition of the water in the [Orionis] disc is very similar to that of comets in our own solar system.”
Researchers used the Atacama Large Millimeter/Submillimeter Array (Alma), made up of 66 radio telescopes in northern Chile, to observe V883 Orionis.
Water there is frozen in the outermost part of this disc so the instruments were unable to detect it.
But an outburst of energy from the star heated the inner disc to a temperature in which water is gaseous, and the astronomers were able to identify its chemical signatures.
From there, they determined the composition of the water and mapped its distribution within the disc.
They said the V883 Orionis disc contains at least 1,200 times the amount of water in all Earth’s oceans.
The team, whose work was published in the journal Nature, also detected the presence of heavy water, in which water molecules are made with heavy isotopes of hydrogen known as deuterium.
Water with high deuterium content can only form if there is enough energy to power the reaction that binds hydrogen, oxygen and deuterium.
Heavy water occurs naturally on Earth but in smaller quantities — at a proportion of about one heavy water molecule in 3,200 normal water molecules.
As normal and heavy water form under different conditions, their ratio can be used to trace when and where it was formed.
In this instance, scientists believe Earth got its water from icy asteroids or comets from outside the solar system.
“We can think of the path of water through the universe as a trail,” Mr Tobin said.
“Until now, the chain of water in the development of our solar system was broken.
“V883 Orionis is the missing link in this case and we now have an unbroken chain in the lineage of water from comets and protostars to the interstellar medium.”
V883 Orionis is a protostar, which means it is still gathering mass in the form of rotating discs of gas and dust from its parent molecular cloud.