Science & Technology

Analysis of ancient cosmic dust was able to solve the mystery of the origin of Earth’s water

Meteorites on the way to the earth and meteorites that break through the atmosphere. Credits: Elements of this image provided by NASA-3 Drender’s Earth Map.Courtesy of University of Glasgow

An international team of scientists may have solved an important mystery about the origin of Earth’s water after revealing compelling new evidence pointing to the unlikely culprit, the Sun.

In a recent paper published in a journal Nature Astronomy, UK, Australia, and a team of American researchers show how new analyzes of ancient asteroids suggest that extraterrestrial dust particles carried water to Earth when the planet was formed. explain.

The water in the particles is produced by space weathering, a process in which charged particles from the sun, known as the solar wind, change the chemical composition of the particles to produce water molecules.

This discovery can answer the long-standing question of where the extraordinarily water-rich Earth got the ocean that covers 70% of its surface. This is far more than any other rocky planet in our solar system. Also, future space missions may help find water sources in an airless world.

Planetary scientists have been confused about the sources of the Earth’s oceans for decades. According to one theory, a type of water-carrying space rock known as a C-type asteroid may have brought water to the planet in the final stages of its formation 4.6 billion years ago.

To test that theory, scientists have previously analyzed the isotope “fingerprint” of a mass of C-type asteroids that fell to Earth as a water-rich carbonaceous chondrite meteorite. If the ratio of hydrogen to deuterium in meteorite water matches the ratio of terrestrial water, scientists can conclude that type C meteorites are probably the source.

The results were not very clear. The deuterium / hydrogen fingerprints of some water-rich meteorites did match the Earth’s water, but many did not. On average, the liquid fingerprints of these meteorites did not match the water found in the Earth’s mantle and ocean. Instead, the Earth has a different, slightly lighter isotope fingerprint.

In other words, some of the Earth’s water must have come from C-type meteorites, but the forming Earth must have received water from at least one isotope source originating from elsewhere in the solar system.

The University of GlasgowThe leading team used a state-of-the-art analysis process called atom Probe tomography examines samples from different types of cosmic rocks known as S-type asteroids that orbit closer to the Sun than C-type. The samples they analyzed were from an asteroid called Itokawa, which was collected by the Japanese space probe Hayabusa and returned to Earth in 2010.

Creation of water molecules from asteroid dust

The figure showing the solar wind (+) that creates water molecules from the dust of the Itokawa asteroid.Credit: University of Glasgow

Atom probe tomography allowed the team to measure the atomic structure of a particle one atom at a time and detect individual water molecules. Their findings indicate that space weathering produced a significant amount of water just below the surface of dust-sized grains from Itokawa.

The early solar system was a very dusty place, providing water of many opportunities to be produced under the surface of dust particles floating in space. Researchers suggest that this water-rich dust would have fallen into the early Earth along with C-type asteroids as part of the Earth’s oceanic supply.

Dr. Luke Daly, Faculty of Geography and Earth Sciences, University of Glasgow, is the lead author of this paper. Dr. Daily said: “The solar wind is primarily a flow of hydrogen and helium ions that are constantly flowing from the sun to space. When these hydrogen ions hit an airless surface, such as an asteroid or dust particles in space, from the surface. It can penetrate tens of nanometers below and affect the chemical composition of the rock. Over time, the “cosmic weathering” effect of hydrogen ions releases sufficient oxygen atoms from the rock’s material to the asteroid. H2O (water) trapped in the minerals of the universe is produced.

“Importantly, the water from this solar wind produced by the early solar system is isotopically light. It was blown away by the solar wind and drawn into the Earth, which was formed billions of years ago. It strongly suggests that fine-grained dust may be the cause of the lost reservoir of planetary water. “

Asteroid Itokawa

Itokawa’s curious and varied terrain and lack of impact craters indicate that it is a rubble pile asteroid. Credit: JAXA

Professor Phil Brand, a prominent professor of Earth and Planetary Sciences at Curtin University and co-author of the dissertation, said: Distribution of Itokawa’s dust particles that orbit the Sun in an 18-month cycle. It turns out that this fragment of the space-weathered rim contains enough water. Scale this up to about 20 liters per cubic meter of rock. “

Professor Michel Thompson, co-author of the Department of Earth, Atmosphere and Planetary Sciences at Purdue University, said: It provides extraordinary insights into how small dust particles in space can help balance books on the isotopic composition of Earth’s water, and new clues to help solve the mystery of its origin. Will give you. “

The researchers took great care to ensure that the test results were accurate and conducted additional experiments with other sources to verify the results.

Dr. Daily added: “The Curtin University atomic probe tomography system is world class, but it has never actually been used in the hydrogen analysis we were doing here. We wanted to make sure the results we saw were accurate. I presented preliminary results at the 2018 Moon and Planetary Science Conference and asked if my colleagues in attendance could help validate our findings with their own samples. Fortunately, NASA NASA Johnson Space Center and the University of Hawaii at Manoa, Padu, Virginia, and Northern Arizona University, Idaho, and Sandia National Laboratories all offered assistance. They gave us samples of similar minerals irradiated with helium and deuterium instead of hydrogen, and from the results of atomic probes on those materials, what we saw on Itokawa was of extraterrestrial origin. It soon became clear that there was.

“The colleagues who supported this study are the team of space weathering dreams, so I’m very excited about the evidence we’ve collected. It’s what the early solar system looked like. , And opened the door to a better understanding of how the Earth and its oceans were formed. “

Co-author of this paper, Professor John Bradley of the University of Hawaii at Manoa in Honolulu, added: , The relevance to the Earth’s oceans is much lower, so you would have been skeptical. By showing for the first time that water is produced in-situ on the surface of an asteroid, our study is based on the accumulation of evidence that the interaction of the solar wind with oxygen-rich dust particles actually produces water. I am.

“Because the entire solar nebula was inevitably exposed to abundant dust before the planetesimal accretion began, the water produced by this mechanism is the origin of the planetary waters and perhaps the isotope composition of the Earth’s oceans. Is directly related to. “

Their estimates of how much water the space-weathered surface contains suggests how future space explorers can produce a water supply even on the driest-looking planets.

Professor Hope Ishii, co-author of the University of Hawaii at Manoa, said: ..

“I think it’s reasonable to think that the same space-weathering process that created water on Itokawa happened to some extent in many airless worlds like the Moon and the asteroid Vesta. It may mean that it may be able to handle the supply of fresh water directly from the dust on the surface of the planet. Human life as the process of forming the planet reaches out beyond the earth. It’s exciting to think that it helps to support. “

Dr. Daily added: “NASA’s Artemis project aims to establish a permanent base on the Moon. If there is a similar solar wind reservoir on the Moon that was discovered in Itokawa in this study, it is that. It will be a huge and valuable resource to help you reach your goals. “

The team’s paper entitled “The Contribution of the Solar Wind to the Earth’s Ocean” Nature Astronomy.

For more information on this discovery, see. The mystery of the origin of Earth’s water: the sun is likely to be an amazing source..

Reference: “The Contribution of the Solar Wind to the Earth’s Ocean” by Luke Daly, Martin R. Lee, Lydia J. Harris, Hope A. Ishii, John P. Bradley, and Philip. A. Brand, David W. Saxey, Denis Fougerouse, William DA Rickard, Lucy V. Forman, Nicholas E. Timms, Fred Jourdan, Steven M. Reddy, Tobias Salge, Zakaria Quadir, Evangelos Christou, Morgan A. Cox, Jeffrey A .Aguiar, Khalid Hattar, Anthony Monterrosa, Lindsay P. Keller, Roy Christoffersen, Catherine A. Dukes, Mark J. Loeffler, Michelle S. Thompson, November 29, 2021 Nature Astronomy..
DOI: 10.1038 / s41550-021-01487-w

University of Glasgow, Curtin University, University of Sydney, Oxford University, University of Hawaii at Manoa, Museum of Natural History, National Institute of Ida, Lockheed Martin, National Institute of Sandia, NASA Johnson Space Center, University of Virginia, University of Northern Arizona, University of Purdue all contributed to this paper.

This study was supported by funding from the Science and Technologies Funding Council, which is part of UKRI. Scotland Alliance for Earth Sciences; Environment and Society (SAGES); Arab Emirates (UAE) Seed Grant; US National Aeronautics and Space Administration (NASA); Science Industry Fund (Science Industry Fund); Australian Research Council Discovery Early Career Researcher Awards (ARC DECRA) DE190101307; Australian Research Council LIEF Program (ARC LE130100053); DOE | LDRD | Idaho National Institute (Idaho National Institute) DOE | National Nuclear Security Administration (NNSA)

Analysis of ancient cosmic dust was able to solve the mystery of the origin of Earth’s water Analysis of ancient cosmic dust was able to solve the mystery of the origin of Earth’s water

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