The late origin of life on Earth
An international team of geologists — led by the University of Cologne and involving UNSW scientists — published new findings on the origin of oceans, and thus life, on the planet Earth. A large proportion of the elements thought necessary to form oceans and life — like water, nitrogen, and carbon — arrived on Earth late in its natural history.
In the past, scientists thought these elements were already here at the start of our planet's formation, in the stellar material swirling around the early days of the Sun. But new geological investigations suggest that most of the water on Earth came to the planet only when its formation was nearly complete.
Vivacious elements like water come from asteroids, the planetary building blocks that formed in the outer solar system. Much discussion and controversy have grown in the scientific community about when it was these building blocks made their way down to Earth.
Leader of the study, Dr. Mario Fischer-Gödde from the Institute of Geology and Mineralogy at the University of Cologne, said we're now capable of narrowing down the timeframe with greater precision, according to phys.org
"The rocks we analyzed are the oldest preserved mantle rocks. They allow us to see into the early history of the Earth as if through a window," said Fischer-Gödde.
"We compared the composition of the oldest, approximately 3.8 billion-year-old, mantle rocks from the Archean Eon with the composition of the asteroids from which they formed, and with the composition of the Earth's mantle today."
'Late veneer' and life's genetic fingerprints
But to understand the temporal process, researchers found an abundance of an isotope of a very rare platinum metal called ruthenium, contained in the Archean mantle of the Earth.
"Platinum metals like ruthenium have an extremely high tendency to combine with iron. Therefore, when the Earth formed, ruthenium must have been completely discharged into the Earth's metallic core," added Fischer-Gödde.
These late building blocks of the Earth, which arrived through collisions of the Earth with asteroids or smaller planetesimals, are called "late veneer."
"Our findings suggest that water and other volatile elements such as carbon and nitrogen did indeed arrive on Earth very late in the 'late veneer' phase," said Fischer-Gödde.
With the rise of the coronavirus pandemic, we live in uncertain times. But this is why there's a special pleasure in coming to know the more about one of the most classic mysteries in science: the formation of life's building blocks — and by extension life itself — on Earth.