June 25, 2022

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Earth's crucial meteorites may have formed in the outer solar system: Study

Earth’s crucial meteorites may have formed in the outer solar system: Study

The study also examined the physical and chemical conditions of (representative) outer belt asteroids.


A new study by researchers at the Earth Life Sciences Institute (ELSI) at the Tokyo Institute of Technology has suggested that this asteroid material could have formed far in the early Solar System and then transported around the inner Solar System by processes. mix up. .

The study was published in the “Advances AGU” journal.

Our solar system is thought to have formed from a cloud of gas and dust, called the solar nebula, that began to condense gravitationally about 4.6 billion years ago. As this cloud shrank, it began to rotate and form a rotating disk around the higher gravitational mass at its center, which would become our Sun.

Our solar system inherited its entire chemical makeup from a previous star or stars that exploded as supernovae. Our sun collected a general sample of this material during its formation, but the material remaining in the disk began to migrate due to its tendency to freeze at a certain temperature. When the Sun became dense enough to start nuclear fusion reactions and become a star, it collected a general sample of this material during its formation, but the remains in the disk formed solid matter to form planetary bodies based on their tendency to freeze anywhere. Nowadays. given time. Temperature.

When the Sun radiated the surrounding disk, it created a temperature gradient in the early solar system. For this reason, the inner planets, Mercury, Venus, Earth, and Mars are mostly made of rocks (mainly made up of heavier elements, such as iron, magnesium, and silicon), while the outer planets are made up of rocks. of the lighter elements, in particular hydrogen and helium. carbon, nitrogen and oxygen.

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Earth is believed to have formed partly from carbonaceous meteorites, which are believed to have originated from asteroids in the outer main belt. Telescopic observations of the outer main belt asteroids reveal a common reflection feature of 3.1 mm indicating that their outer layers contain water ice or ammonia clay, or both, which are stable only at extremely low temperatures.

Interestingly, although many evidence suggests that carbonaceous meteorites derive from these asteroids, meteorites recovered from Earth generally lack this feature. The asteroid belt raises many questions for astronomers and planetary scientists.

In this study, a combination of asteroid observations using the Japanese AKARI space telescope and theoretical modeling of chemical reactions in asteroids indicates that the surface minerals in the outer main belt asteroids, especially ammonia-containing mud (NH3), are formed from ice-containing raw materials. NH3 and CO2 which are stable only at very low temperatures and in conditions rich in water.

Based on these findings, this new study suggested that outer main belt asteroids form in distant orbits and differentiate to form different minerals in the water-rich mantle and rock-dominated cores.

To understand the origin of the discrepancies in the measured spectra of carbonaceous meteorites and asteroids, using computer simulations, the team modeled the chemical evolution of several plausible primitive mixtures designed to simulate primordial asteroid materials. They then used these computer models to produce simulated reflection spectra for comparison with those obtained with the telescope.

Their models indicated that to match the spectra of asteroids, the starting material must contain a large amount of water and ammonia, a relatively low abundance of carbon dioxide, and react at temperatures below 70, indicating that asteroids would form much larger. . Presence. Locations in the early solar system. In contrast, the absence of the 3.1 mm feature in the meteorites could be attributed to a possible deeper interaction within the asteroids, where temperatures reached higher values. Therefore, recovered meteorites can sample from deeper parts of asteroids.

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If true, then this study suggests that the Earth’s composition and unique properties were the result of certain aspects of the formation of the solar system. There will be many opportunities to test this model, for example, this study provides predictions about what will be found in the analysis of samples returned by Hayabusa 2. This distant origin of asteroids, if correct, predicts the presence of ammonia and metal salts in samples returned from Hayabusa 2. Analyzes of materials returned by NASA’s OSIRIS-Rex mission will provide further validation of this model.

This study also investigated whether the physical and chemical conditions of the outer main belt asteroids should be able to form the observed minerals. The cold and distant origin of asteroids suggests that there must be great similarities between asteroids and comets and raises questions about how each of these types of bodies formed.

This study suggested that the materials that shaped the Earth may have been formed in faraway places in the early solar system, and then introduced during the particularly turbulent early days of the solar system. Recent observations of protoplanetary disks by the Atacama Large Millimeter/Submatter Array (ALMA) have found many ring structures, believed to be direct observations of planet formation.

As lead author Hiroyuki Kurokawa summarized the work: “Whether the formation of our solar system is a typical outcome remains to be determined, but many measurements suggest that we may soon be able to put our cosmic history into context.”

(Except for the title, this story has not been edited by the NDTV crew and is posted from a syndicated feed.)

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