Meteorites reveal the possible origin of volatile chemicals on Earth

Newswise – By analyzing meteorites, Imperial researchers have discovered the possible distant origin of Earth’s volatile chemicals, some of which are the building blocks of life.

They found that nearly half of Earth’s stock of volatile zinc came from asteroids that originated in the outer solar system – the part outside the asteroid belt that includes Jupiter, Saturn and Uranus. This material is also expected to have provided other important volatiles such as water.

Volatile substances are elements or compounds that change from a solid or liquid state to a vapor at relatively low temperatures. They include the six most common elements found in living things, as well as water. As such, the addition of these materials would be important to the emergence of life on Earth.

Prior to this, researchers believed that most of the volatiles on Earth came from asteroids that formed near Earth. The results reveal important clues about how Earth harbors the special conditions needed to sustain life.

Senior author Professor Marc Recamber, from the Department of Earth Sciences and Engineering at Imperial College London, said: “Our data show that about half of Earth’s zinc stock has been delivered by material from the outer solar system, beyond the orbit of Jupiter. Based on existing models of the early development of the solar system This was completely unexpected.”

Previous research has indicated that Earth formed almost exclusively from inner solar system material, which the researchers conclude is the main source of volatile chemicals on Earth. In contrast, the new findings suggest that the outer solar system played a larger role than previously thought.

Professor Recamber added: “This contribution from outer material to the solar system has played a vital role in creating Earth’s stock of volatile chemicals. It appears that without the contribution of outer solar system material, Earth would have much less volatile matter than we know today – making it drier and possibly unable to nurture and sustain life.”

The results were published today Sciences.

To conduct the study, the researchers examined 18 meteorites of different origins – eleven from the inner solar system, known as non-Carbonaceous meteorites, and seven from the outer solar system, known as carbonaceous.

For each meteorite they measured the relative abundances of the five different forms – or isotopes – of zinc. Then they compared each isotopic fingerprint with Earth samples to estimate how much each of these substances contributed to Earth’s zinc stock. The results indicate that while the Earth only incorporated about 10 percent of its mass of carbonaceous bodies, this material provides about half of the zinc found on Earth.

The researchers say that substances with a high concentration of zinc and other volatile components are also likely to be relatively abundant in the water, giving clues about the origin of Earth’s water.

First author on the paper Rayssa Martins, PhD student in the Department of Earth Sciences and Engineering, said: “We have known for a long time that some carbonaceous material was added to the Earth, but our findings indicate that this material played a major role in establishing our balance of fluctuating elements. , and some of them are necessary for the flourishing of life.”

Next, the researchers will analyze Martian rocks, which harbored water 4.1 to 3 billion years ago before drying out, and the moon. Professor Rekamper said: “The popular theory is that the moon formed when a huge asteroid collided with the embryonic Earth about 4.5 billion years ago. Analysis of zinc isotopes in moon rocks will help us test this hypothesis and determine whether the colliding asteroid played an important role in delivering volatiles, including In that water, to the ground.”

This work was funded by the Science and Technology Facilities Council (STFC – part of UKRI) and Rayssa Martins is funded by a PhD scholarship at Imperial College London.