Asteroids from the inner solar system likely provided Earth with water, say scientists, the first such study to examine the exact extent of water from past impact zones.
A new study, published today in Science, says that asteroids were the source. The authors, led by Conel Alexander of the Carnegie Institution of Washington, in Washington DC, analysed the isotopic abundances of nitrogen and hydrogen in 86 primitive meteorites, and found that they coordinate with Earth’s.
The findings contradict prevailing theories about the relationship between comets and water-bearing carbonaceous chondrites and suggest that meteorites, and their parent asteroids, are the most likely sources of Earth’s water. Previous studies had suggested that water on Earth may have come from comets.
The study found that asteroids, rather than comets, are the source of Earth’s water. Both asteroids and comets are found in a region of the solar system known as the asteroid belt, which occupies a wide swathe of space between the orbits of Mars and Jupiter. However, comets with their icy tails would have been born in the chillier region of space between Saturn and Jupiter and then migrated into the asteroid belt.
The amount of deuterium in celestial bodies’ water ice sheds light on where the objects formed in the solar system’s early days. In general, bodies that took shape farther from the sun have relatively higher concentrations of deuterium, researchers said.
“Our results provide important new constraints for the origin of volatiles in the inner solar system, including Earth,” said Alexander. “And they have important implications for the current models of the formation and orbital evolution of the planets and smaller objects in our solar system.”
Early Earth was likely a hot and dry place. Any water forming on the surface of the early Earth was boiled away from the scorching crust. Ultraviolet light from the newly formed Sun stripped hydrogen atoms from the water molecules leaving no rain to fall back on the surface. The team of researchers analyzed samples from 86 carbonaceous chondrites. These primitive meteorites are thought to be key sources of the early Earth’s volatile elements, such as hydrogen and nitrogen.
The team of researchers said the results of the study could alter our understanding how the evolution of the solar system and life on Earth.
“Our results provide important new constraints for the origin of volatiles in the inner solar system, including the Earth,” Alexander said. “And they have important implications for the current models of the formation and orbital evolution of the planets and smaller objects in our solar system.”
Alexander’s team included Carnegie’s Larry Nitler, Marilyn Fogel, and Roxane Bowden, as well as Kieren Howard from the Natural History Museum in London and Kingsborough Community College of the City University of New York and Christopher Herd of the University of Alberta.
The study appeared July 12 online in the journal Science.