According to new research, meteorites that formed in the early days of the solar system may contain liquid water, giving credence to the theory that meteorites brought water and other precursors of life to our planet billions of years ago.
Carbonaceous chondrites are a special group of meteorites that date back to the formation of the solar system. When pieces of them are found on Earth, they have been found to contain pieces of seductive information, such as minerals that only appear in the presence of water and organic compounds such as amino acids, some of the basic components of life.
As a result, carbonaceous chondrites have become one of the main candidates for how water ended up on Earth. A fantastic way to know for sure would be if a chondrite — which, though rare among its fallen meteorite compatriots, still hits the Earth regularly — landed with water on it, and we were lucky enough to see the rock and retrieve this.
It is a high order. The asteroid Ryugu was recently dried in water for a long time before Japan arrived with its Hayabusa2 spacecraft. Until now, scientists were aware that fluid flow occurred in carboniferous chondrites at some point, but they did not know to what extent this flow could have occurred. Earlier dating methods showed that water was present in these rocks early, about 4.5 billion years ago, shortly after the formation of the Earth.
“All this leads to the hypothesis that any alteration and any presence of water was very old. So our test had to say: could there be a young alteration? “ Simon Turner, an isotope geochemist at Macquarie University in Sydney, Australia, said in a video call. “That is, there is still ice in these meteorites.” Turner is the lead author of a new article describing the flow of liquids in carbonaceous chondrites, published this week in Scientific Reports magazine.
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A team of researchers from Macquarie University, Florida State University and the Natural History Museum in Paris have discovered that these carbonaceous chondrites have had a certain amount of liquid in the last hundreds of thousands of years, very recently, by which relates to space and geological time scales.
All meteorites fall, but only those that are seen are called “falls” afterwards. Turner’s team only used carbonate chondrite falls in their research, because these fresh rocks from space have a clear timestamp when they arrived and the context of what they came in contact with on Earth (i.e. , with which they could be contaminated). The meteorites included in the study came from everywhere: one came from Sutter’s Mill, where the California gold rush began, while another landed on an icy lake in Russia, among many other places in the world.
The research team took samples of these space rocks and dated their water flow with uranium-thorium dating, in which the isotopes of the two elements can be measured to discern age. In this case, the issue was not the age of these meteorites themselves, but the age at which the liquid moved inside the rock. Uranium has a very mobile fluid, while thorium does not, so, seeing when uranium moved inside the meteorite relative to thorium, the team could deduce when the water spun around.
“If there was ice in the bodies, and if there was any reason why the ice melted and moved, and occurred in the last million years, you should expect a differential behavior of uranium and thorium,” said Turner.
In other words, when liquid flows, either on a space rock or along a river bed, it changes the isotopes around it, leaving a short-term record of flow. This signature disappears if too much time passes. If the isotopes moved in a million years, specifically, the computer would detect this disruption.
The freshness of the liquid the movement found in some of the equipment samples is exciting, meaning that carbonaceous chondrites can contain ice very well if they had a fluid flow liquid a few hundred thousand years ago.
Edward Young, a UCLA geochemist who was not affiliated with the recent paper, said in an email that the new research was “very interesting” and “elegant.” He pointed to the other one recently, scientists have known the widespread flow of water to the asteroid Bennu, thanks to NASA let’s go OSIRIS-REx mission.
The next step would be to test spacecraft that did not fall like a fireball through the Earth’s atmosphere, a violent process that hides exactly how the ice of these asteroids melted (samples provided by a spacecraft would be useful). Meanwhile, researchers will move with the fallen space rocks, watching the sky for new evidence that could fall.