An ancient meteorite 2.29 billion years ago changed the Earth and may have contributed to the emergence of life: what scientists have learned
The oldest meteorite impact on Earth known to scientists, which occurred 2.29 billion years B.C., may have created the conditions for the origin of early life on the planet. It also changed the chemical composition of the Earth's crust.
This is according to a study published in the journal Earth and Planetary Science Letters. The authors examined what was left of the world's oldest known impact crater, Yarrabubba in Western Australia.
"We found evidence that hot water circulated in cracks in the rock after the impact, possibly because the impact melted some of the ice that covered most of the planet at the time," Andreas Sametzer, PhD, and his colleague, geochronology professor Chris Kirkland of Curtin University in Australia, told The Conversation in a paper for The Conversation.
They hypothesize that water in rock cracks could have created a niche for early life forms.
"Its presence also has implications for our understanding of how metal ore deposits form in the Earth's crust," the researchers added.
Around 200 major meteorite impact sites have been documented across the planet, but Yarrabubbi is home to the oldest of them all. More than two billion years ago, a space rock slammed into the continental crust at Yarrabubbi, which underwent intense changes as a result of the impact.
The meteorite impact created a crater about 70 kilometers in diameter, which today has eroded to the size of a small hill.
In conducting research to determine the age of the impact crater, scientists measured the ratio of uranium and lead isotopes, "acting like a stopwatch counting down the time since the mineral was formed."
Different isotopes of an element behave the same way in chemical reactions, but contain different numbers of neutrons inside the atom. This makes some isotopes unstable: over time, they radioactively decay into different elements. Measuring isotopes therefore allows us to determine the age because uranium decays into lead over time, and scientists know the rate at which this decay occurs.
The researchers analyzed the isotopic composition of lead in mineral grains from the crust surrounding the crater at Yarrabubbi and were able to determine the composition of the fluid from which the mineral grew.
"We found a wide range of lead isotopic compositions as well as new uranium-bearing minerals that grew in the cracks of the grains during the impact, triggering new stopwatches," the scientists said.
The only plausible explanation for this chemical change in the crust, according to the researchers, is that the impact created networks of circulating hot water that seeped into cracks throughout the rock.
"In the case of Yarrabubba, the water may well have come from a meteorite impact on an ice sheet, since 2.29 billion years ago most of the world was covered by ice," the scientists said.
The hot liquid systems formed by the impact could have contributed to the emergence of early life, they suggested.
"Researchers have demonstrated that microbial communities can flourish where heat, water and nutrients meet crushed rock: these are the conditions that can create collisions. Some even suggest that collision is a fundamental part of planetary evolution, necessary to create a habitable planet," the scientists noted.
Note that the earliest life forms formed on Earth about 3.8 billion years ago.
Scientists also noted that their study provided insight into how hot water formed during collisions can carry metals that form ore deposits.
Such deposits usually form where there is a geologic structure, such as a fracture in a rock formation, into which metals can be moved by fluids.
"Impacts certainly erode the Earth's crust, but they also allow hot water to circulate. If there is metal in the rocks, this hot water can transport and concentrate those metals into a richer deposit," the scientists said.
Earlier OBOZREVATEL told about the research of scientists who suggested that life on Earth could have originated thanks to a radioactive meteorite.