A tiny meteorite is upending what scientists previously believed about when the planets of our solar system formed.
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New evidence found in fragments from a meteorite known as Northwest Africa 12264 — a 50-gram piece of space rock — suggests that rocky planetslike Earth and distant icy bodies may have formed at the same time. This contradicts the long-held belief that planets closer to the Sun formed before those in the outer solar system, beyond the asteroid between Mars and Jupiter.
Planets form within the rotating disks of gas and dust surrounding young stars, where particles collide and stick together through a process known as accretion. As the rocky planets in formation heat up, they begin to differentiate, forming distinct inner layers known as a core, mantle, and crust.
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Scientists believed that the inner rocky planets of our solar system—Mercury, Venus, Earth, and Mars—formed first (about 4.566 billion years ago), while the gas giants and icy bodies of the outer solar system formed a little later (about 4.563 billion years ago), due to the cooler temperatures at greater distances from the Sun. It was also believed that the more distant rocky planets formed more slowly, because their higher water and ice content slowed the heating and growth of cores .
Analysis of the meteorite's composition revealed a ratio of chromium to oxygen that suggests it came from the outer solar system. Using precise isotopic dating methods, the researchers determined that the rock formed 4.564 billion years ago — just two to three million years after the first solid materials in the solar system. Until now, such an early formation was thought to be limited to bodies in the inner solar system, according to a statement accompanying the new study.
According to the researchers, evidence showing that rocky planets beyond Jupiter formed just as quickly and simultaneously as the inner planets could fundamentally change our understanding of how planets form — not just in our solar system, but in planetary systems throughout the universe.
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Their findings were published July 4 in the scientific journal Communications Earth & Environment.
Source: livescience
