A large demolition derby, with a chaotic mess of asteroids and ever-collapsing planets, took place in the early solar system between 7.8 million and 11.7 million years after the sun formed, according to a new analysis of iron meteorites as a was once part of metallic asteroid cores.
An international team of researchers analyzed isotopes of palladium, silver and platinum in 18 iron meteorites found on Earth to better understand the development of their parental bodies. Metallic asteroids contain dense iron nuclei and iron meteorites derived from these nuclei, blown up by collisions with other asteroids.
Palladium 107 undergoes radioactive decay to silver 107 with a half-life of 6.5 million years. Previous measurements of the relative occurrences of the two isotopes with a mass spectrometer had already indicated that asteroid nuclei that the meteorites were once part of cooled rapidly. The question was when did this rapid cooling occur?
To limit the date, the research team – led by Alison Hunt, a senior researcher at ETH Zurich and the National Center of Competence in Research Planets in Switzerland – refined the mass spectrometer process and searched for isotopes of the rare metal platinum that originated. from cosmic rays met the meteorites as they traveled through space.
“Our additional measurements of platinum isotope deposits allowed us to correct the silver isotope measurements for distortions caused by cosmic irradiation of the samples in space,” Hunt said in a statement. “So we could date the time of the collisions more accurately than ever before.”
The dates that Hunt’s team arrived at were between 7.8 million and 11.7 million years later the formation of the solar system – a relatively short period of time in its 4.5 billion-year history, although studies of other meteorites may extend the era.
The finding suggests that the early Solar system was extremely chaotic. The planets would not even have stopped forming, and asteroids and protoplanets would have collided frequently and removed the silicate mantle from some of the larger asteroids to expose their metallic nuclei in space and allow them to cool rapidly before further collisions crushed the nuclei. .
“Everything seems to have broken down by that time,” Hunt said.
Something caused this chaos, and Hunt’s team believes that it was largely related to the solar nebula, the gas cloud that formed the sun. Then the remnants of that cloud settled on a disk around the young star. As the gas cooled, dust and ice condensed out of it, which through a process called accumulation built up in the planets, asteroids and comets which we are familiar with today.
But the planets had only a limited time to gather; as the sun gradually turn on, the solar wind began to blow away the remnants of the solar nebula. Young planetary bodies had been collected by friction with the gas, which slowed down their orbital speed. Without the gas to hold back these planetary bodies, there must have been a period of chaos where planetary orbits went berserk, leading to a plethora of collisions, before the latter calmed down, the researchers explained.
But other events around the same time could also have contributed to the chaos, the team noted. The gas giant planets – in particular, Jupiter and Saturn migrated around the early solar system, and their gravitational influence disrupted the orbits of smaller bodies, leading them to form asteroid belt and that Kuiper belt.
One model in particular, known as the “Grand Tack”, claims that Jupiter migrated in the system, as close to the sun as March is today, before Saturn seriousness caused Jupiter to migrate outward again to its current position. The Grand Tack model predicts that this event would have taken place about 10 million years into the history of the solar system.
However, proving what happened 4.5 billion years ago is the challenge, and this new study that suggests the fate of the asteroids that produced iron meteorites provides new evidence of how violent the early solar system could be.
More information may appear when NASA’s Psyche missionwhich will be launched later this year, arrives at the metallic asteroid Psyche 2026.
The research was published online on May 23 in the journal Nature astronomy.
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