Explosion! Collision! This is the early solar system

Iron meteorites suggest millions of years of turmoil in early solar system

Meteorites provide clues to dramatic events that occurred in the early days of the solar system.

Asteroid impacts in the early solar system exposed their iron cores to space, which allowed the asteroids to cool rapidly.

Image credit: NASA, Jet Propulsion Laboratory, California Institute of Technology

According to a new research result, which is an analysis of the cores of iron meteorites of metallic asteroids, it is shown that between 7.8 million and 11.1 million years after the formation of the solar system, a huge and violent explosion occurred in the early solar system, and asteroids and asteroids in formation continued to collide with each other.

In order to gain a deeper understanding of the parent body evolution of iron meteorites, an international research team analyzed the isotopes of palladium, silver and platinum in 18 iron meteorites found on Earth. The analysis results showed that metallic asteroids have dense iron cores, and iron meteorites come from these iron cores, which are produced during collisions with other asteroids.

Palladium 107 undergoes radioactive decay to silver 107 with a half-life of 6.5 million years. Previous mass spectrometry measurements of the relative abundance of the two isotopes have shown that the core of the asteroid, which is made of meteorites, has experienced rapid cooling. The question is, when did this rapid cooling occur?

In order to shorten the research time, a research team led by Allison Hunt, a senior scientist at ETH Zurich and the Swiss National Center for Planetary Research, improved the detection process of the mass spectrometer to detect isotopes of the rare metal platinum produced by cosmic rays hitting meteorites in space.

"Additional measurements of the abundance of platinum isotopes corrected for distortions in the silver isotope measurements caused by cosmic radiation from space, so we can date the collision more precisely than ever before," Hunt said in a statement.

Hunter's team came up with a date between 7.8 million and 11.1 million years after the formation of the solar system, and while studies of other meteors may extend that time, it's a relatively short span in the 4.5-billion-year history of the Sun.

The results of this study indicate that the early solar system was extremely chaotic. Before the planets formed, asteroids frequently collided with protoplanets, which stripped away the silicate mantles of larger asteroids, exposing their metallic cores to space. This allowed the asteroids to cool rapidly before the explosions that caused them to break apart.

An iron meteorite (part of the Barringer crater formed by an asteroid impact in Arizona)

Image credit: NASA

“At that point, everything was falling apart,” Hunter said.

Something caused this chaos, and Hunter's team thinks it has to do with the dissipation of the solar nebula, the gas cloud from which the sun formed. The remnant of the nebula then formed a disk around the young star, and as the gas cooled, dust and ice condensed, accreting to form the planets, asteroids and comets we know today.

However, the time for these planets to gather is very limited. As the sun gradually formed, the solar wind blew away the remnants of the solar nebula. The friction of the gas formed young stars, and this friction slowed down the orbital speed of the stars. The researchers explained that if the planetary body loses the gas restraint, it will definitely experience a period of chaos, such as the planetary orbit out of control, and lead to a series of stellar collision events, and then these planets will return to peace.

In 2026, the spacecraft will visit the metallic asteroid Psyche. (Image credit: California Institute of Technology, NASA's Spray Propulsion Laboratory, Arizona State University)

However, the team notes that other things that happened during the same period could have also contributed to the chaos in the solar system. In particular, the giant gas planets, such as Jupiter and Saturn, migrated around the early solar system. Their gravity disrupted the orbits of smaller bodies, causing them to form the asteroid belt and the Kuiper belt.

One particular model, called the "Grand Strategy," suggests that Jupiter once migrated within the solar system, and was very close to the sun, about the distance between Mars and the sun today. Under the influence of Saturn's gravity, Jupiter migrated out of the solar system again and moved to its current position. The "Grand Strategy" model estimates that this migration occurred about 10 million years ago.

However, proving what happened 4.5 billion years ago is a huge challenge. Studying the formation and destruction of the asteroids that produced the iron meteorites could provide new evidence of just how violent the early solar system was.

Later, NASA will launch the Psyche mission, which will bring back more data and information. The Psyche spacecraft will arrive at the metallic asteroid in 2026.

The research will be published online in the journal Nature Astronomy.

BY:Keith Cooper

FY: Wan Lin

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