Neon isotopes from glassy rocks on the ocean floor may hold the key to understanding how Earth formed 4.5 billion years ago.
Depending on how slowly or quickly our early planet assembled from the solar nebula, scientists say the concentration of different gases at the surface would vary.
A new study analyzing deep-ocean neon, said to be the closest we can get to Earth’s mantle, suggests the young planet was born rapidly from clouds of dust and gas around the sun, which trapped water and gases within their midst.
The three leading ideas about Earth’s formation from a protoplanetary disk propose different timelines and processes for how our planet came to be.
While the first suggests the process happened quickly, over about two to five million years as it trapped gas from the nebula, another says Earth formed from dust particles irradiated by the sun, which condensed into mini ‘planetismals’ before coming together.
The third suggests Earth’s formation was a slow process relying on water-rich carbonaceous chondrite meteorites to deliver gases.
‘We’re trying to understand where and how the neon in Earth’s mantle was acquired, which tells us how fast the planet formed and in what conditions,’ said postdoctoral researcher Curtis Williams, from the University of California, Davis.
According to the researcher, neon can stand in for water, carbon dioxide, and nitrogen when looking for their origins.
Neon, unlike the other life-essential chemicals, is inert, meaning I does not change as a result of chemical and biological processes.
‘So neon keeps a memory of where it came from even after four and a half billion years,’ says University of California Davis Professor Sujoy Mukhopadhyay.
In the study, the team measured neon isotopes that became trapped in the mantle when Earth formed.
Of its three isotopes, neon-21 is the only whose amount changes over time, as it’s formed by the radioactive decay of uranium.
The researchers analyzed neon gas found in bubbles within pillow basalts on the ocean floor using a mass spectrometer to establish the ratios for the solar nebula model.
According to the researchers, the ratios found in the basalts did not line up with the ‘irradiated particles’ explanation or the ‘late accretion’ model.
‘This is a clear indication that there is nebular neon in the deep mantle,’ Williams said.
The team also says the findings could serve as a guide in the search for potentially habitable planets, as it’s a marker for other volatile compounds that are essential for life.
‘There are a couple of ways dust could be depleted from the disk, and one of them is that they are forming planets,’ Williams said.
‘We can observe planet formation in a gas disk in other solar systems, and there is a similar record of our own solar system preserved in Earth’s interior,’ Mukhopadhyay said.
‘This might be a common way for planets form elsewhere.’