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Key points:
- Analysis of meteorites from varying origins around the solar system has revealed the origin of Earth’s zinc.
- About half of Earth’s zinc inventory was delivered by material from the outer solar system, beyond the orbit of Jupiter.
- The team will now analyze rocks from Mars and the Moon, looking for other volatile constituents.
By analyzing meteorites, researchers at the Imperial College London have uncovered the likely far-flung origin of Earth’s volatile chemicals, some of which form the building blocks of life.
They found that around half the Earth’s inventory of the volatile element zinc came from asteroids originating in the outer solar system—the part beyond the asteroid belt that includes the planets Jupiter, Saturn, and Uranus. This material is also expected to have supplied other important volatiles, including water.
Prior to this, researchers thought that most of Earth’s volatiles came from asteroids that formed closer to the Earth. The findings reveal important clues about how Earth came to harbor the special conditions needed to sustain life.
In the study, published in Science, researchers examined 18 meteorites of varying origins —11 from the inner solar system, and seven from the outer solar system.
For each meteorite, they measured the relative abundances of the five different isotopes of zinc. They then compared each isotopic fingerprint with Earth samples to estimate how much each of these materials contributed to the Earth’s zinc inventory. The results suggest that, while the Earth only incorporated about 10% of its mass from carbonaceous bodies, this material supplied about half of Earth’s zinc.
“Our data show that about half of Earth’s zinc inventory was delivered by material from the outer solar system, beyond the orbit of Jupiter. Based on current models of early solar system development, this was completely unexpected,” said senior author Mark Rehkämper, professor in the department of earth science and engineering.
The researchers say material with a high concentration of zinc and other volatile constituents is also likely to be relatively abundant in water, giving clues about the origin of Earth’s water.
Next, the team will analyze rocks from Mars, which harbored water 4 to 3 billion years ago before drying up, as well as the Moon.
“The widely held theory is that the Moon formed when a huge asteroid smashed into an embryonic Earth about 4.5 billion years ago. Analyzing zinc isotopes in moon rocks will help us to test this hypothesis and determine whether the colliding asteroid played an important part in delivering volatiles, including water, to the Earth,” said Rehkämper.