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A new understanding of the extraterrestrial origin of Earth’s lakes, rivers and oceans

The new study, published March 15 in the journal Nature, It brings scientists one step closer to answering this question. Sune Nielsen, a research associate in the Department of Geology and Geophysics at the Woods Hole Institution of Oceanography (WHOI), is one of the authors of a study that analyzed molten meteorites floating in space for the four and a half billion years since the formation of the Solar System. Years ago. The researchers discovered that these meteorites had extremely low water content – ​​in fact, they were some of the driest extraterrestrials ever measured. These results, which allow researchers to rule them out as the primary source of water on Earth, could have important implications for the search for water and life on other planets. It also helps researchers understand the unlikely conditions that make Earth a habitable planet.

“We wanted to understand how our planet gets its water, because it’s not entirely clear,” Newcombe said. Said. “Making water and having surface oceans on a small and relatively close planet is a challenge”

A team of researchers has analyzed seven molten or achondritic meteorites that crashed into Earth billions of years after they separated from at least five planetary objects, objects that collided to form our solar system’s planets. In a process known as melting, many of these planetesimals were warmed by the decay of radioactive elements in the early Solar System’s history, causing them to break up into layers containing a crust, mantle, and core.

Since these meteorites have recently fallen to Earth, this experiment was the first time someone had measured their water content. UMD geology graduate student Liam Peterson used an electron microprobe to measure levels of magnesium, iron, calcium, and silicon, then joined Newcomb at the Carnegie Institute for Science Earth and Planetary Laboratory to measure water content with a secondary ion mass spectrometry instrument.

“The problem with analyzing water in extremely dry materials is that any terrestrial water on the surface of the sample or inside the measuring instrument can be easily detected and the results can be skewed,” said co-author Conel Alexander, a researcher at the Carnegie Institution. Science.

To reduce contamination, the researchers first baked their samples in a low-temperature vacuum oven to remove surface water. Before analyzing the samples in a secondary ion mass spectrometer, they had to be dried again.

“I had to leave the samples under a turbopump – a really high vacuum – for over a month to extract enough Earth water,” Newcombe said.

Some of the meteorite samples came from the inner solar system where Earth is located and conditions are generally considered to be hot and dry. Other, rarer specimens came from colder and icy regions of our planetary system. Although it is generally believed that water came to Earth from the outer Solar System, it has not yet been determined what kinds of objects may have carried this water through the Solar System.

“We knew that many objects in the outer Solar System differ, but we indirectly assumed that they must contain a lot of water because they belong to the outer Solar System,” said WHOI’s Nielsen. “Our article shows that this is certainly not the case. As soon as the meteorites melt, there is almost no water left.”

After analyzing the achondrite meteorite samples, the researchers found that water made up less than two parts per million of their mass. By comparison, the wettest meteorites, a group called carbonaceous chondrites, contain up to about 20 percent by weight, that is, 100,000 times more water than the meteorite samples studied by Newcombe and colleagues.

This means that the warming and melting of planetesimals is causing almost complete loss of water, regardless of where in the Solar System these planetesimals come from and how much water they come from. Newcomb and co-authors found that contrary to popular belief, not all outer solar system objects are rich in water. This led them to conclude that the water was probably brought to Earth via unmelted or chondritic meteorites.

Newcomb said his findings have applications beyond geology. Scientists from many disciplines, and exoplanet researchers in particular, are interested in the origin of Earth’s water because of its deep connection to life.

“Water is thought to be an ingredient for the development of life, so once we look around the universe and find all these exoplanets, we begin to decide which of these planetary systems might be a potential host for life,” Newcombe said. Said. “To understand these other solar systems, we want to understand our own.”

Source: Port Altele



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