Meteorites That Helped Form Earth May Have Formed In The Outer Solar System, Study Suggests

Tokyo: A new study by researchers at the Tokyo Institute of Technology’s Earth-Life Science Institute (ELSI) has suggested that these asteroid materials could have formed very far away in the early solar system and then been transported around the system. internal solar by chaotic mixing processes.

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

Our solar system is thought to have formed from a cloud of gas and dust, called the solar nebula, which began gravitationally condensing around 4.6 billion years ago. As this cloud contracted, it began to spin and form into a spinning disk around the highest gravity mass at its center, which would become our Sun.

Our solar system inherited all of its chemical composition from an earlier star or stars that exploded as supernovae. Our Sun picked up a general sample of this material as it formed, but the residual material in the disk began to migrate due to its propensity to freeze at a given temperature. As the Sun became dense enough to initiate nuclear fusion reactions and become a star, it picked up a general sample of this material during its formation, but the remnants in the disk formed solid material to form planetary bodies based on its propensity to freeze at any given time. Temperature.

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

Earth is thought to have formed partly from carbonaceous meteorites, which are thought to have originated from asteroids in the outer main belt. Telescopic observations of outer main belt asteroids reveal a common feature of 3.1mm reflectance that suggests their outer layers host either water ice or ammonia clays, or both, which are only stable at very low temperatures.

Interestingly, although several lines of evidence suggest that carbonaceous meteorites are derived from such asteroids, meteorites recovered from Earth generally lack this feature. The asteroid belt therefore 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 suggests that surface minerals present on outer main belt asteroids, in particular clays containing ammonia (NH3), form from raw materials containing Ice NH3 and CO2 which are only stable at very low temperatures and under water-rich conditions.

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

To understand the source 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 primitive asteroid materials. They then used these computer models to produce simulated reflectance spectra to compare with those obtained by telescope.

Their models indicated that to match the asteroid spectra, the starting material had to contain a significant amount of water and ammonia, a relatively low abundance of CO2, and react at temperatures below 70, suggesting that the asteroids would are formed much further than their current presence. locations in the early solar system. In contrast, the absence of the 3.1 mm feature in meteorites can be attributed to a possibly deeper reaction inside the asteroids where temperatures reached higher values. Thus, recovered meteorites can sample deeper parts of asteroids.

If true, this study suggests that the formation of the Earth and its unique properties resulted from particular aspects of the formation of the solar system. There will be several opportunities to test this model, for example, this study provides predictions on what analysis of samples returned by Hayabusa 2 will find. This distant origin of asteroids, if correct, predicts that there will be ammonia salts and minerals in samples returned by Hayabusa 2. Further verification of this model will be provided by analyzes of materials returned by the mission. NASA’s OSIRIS-Rex.

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

This study suggested that the materials that formed the Earth may have formed very far away in the early solar system, then were introduced during the solar system’s particularly turbulent early days. Recent observations of protoplanetary disks by the Atacama Large Millimeter/submillimeter Array (ALMA) have found numerous ring structures, which are thought to be direct observations of planetesimal formation.

As lead author Hiroyuki Kurokawa summed up 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.”

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