Nola Taylor
Scientific American
A new study suggests primordial seawater may lurk hidden at the hearts of many comets
The mysterious source of Earth’s water has intrigued generations of scientists. Learning how this liquid—the cornerstone of life as we know it—made its way to our planet has sweeping implications, for the possibility of alien biospheres not only elsewhere in the solar system but also on worlds orbiting other stars. But understanding how water arrived on Earth has proven surprisingly difficult.
After the sun formed from a cloud of dust and gas, the remaining protoplanetary disk of material was probably rich in water’s raw ingredients, hydrogen and oxygen. But conventional wisdom holds that the newborn star’s radiance boiled away much of those volatile gases from the inner solar system, leaving mostly dry material from which to build Earth and the other rocky planets. The majority of Earth’s moisture must have arrived later, by some other means.
For decades, scientists considered icy comets of the outer solar system as the most likely suspects, until observations revealed that most comets’ compositions did not quite match that of Earth’s oceans. And so consensus shifted toward asteroids as the source of Earth’s seas, since these rocky bodies also contain nontrivial amounts of water and are conveniently located close by, where they could have easily rained down on the young Earth. Now, however, an investigation of comet 46P/Wirtanen suggests that the bulk of Earth’s water may have come from comets after all, even though asteroids likely still played an important role.
Read more
Scientific American
A new study suggests primordial seawater may lurk hidden at the hearts of many comets
The mysterious source of Earth’s water has intrigued generations of scientists. Learning how this liquid—the cornerstone of life as we know it—made its way to our planet has sweeping implications, for the possibility of alien biospheres not only elsewhere in the solar system but also on worlds orbiting other stars. But understanding how water arrived on Earth has proven surprisingly difficult.
After the sun formed from a cloud of dust and gas, the remaining protoplanetary disk of material was probably rich in water’s raw ingredients, hydrogen and oxygen. But conventional wisdom holds that the newborn star’s radiance boiled away much of those volatile gases from the inner solar system, leaving mostly dry material from which to build Earth and the other rocky planets. The majority of Earth’s moisture must have arrived later, by some other means.
For decades, scientists considered icy comets of the outer solar system as the most likely suspects, until observations revealed that most comets’ compositions did not quite match that of Earth’s oceans. And so consensus shifted toward asteroids as the source of Earth’s seas, since these rocky bodies also contain nontrivial amounts of water and are conveniently located close by, where they could have easily rained down on the young Earth. Now, however, an investigation of comet 46P/Wirtanen suggests that the bulk of Earth’s water may have come from comets after all, even though asteroids likely still played an important role.
Read more
