There is no doubt that young solar systems are chaotic places. Cascading collisions defined our young Solar System as rocks, blocks, and planetesimals repeatedly collided.
A new study based on pieces of asteroids that crashed into Earth sets a timeline apart from this chaos.
Astronomers know that asteroids have remained essentially unchanged since their formation at the beginning of the Solar System billions of years ago.
They are like rocky time capsules that contain scientific clues from that important time because differentiated asteroids had mantles that protected their interiors from space weather.
But not all asteroids remained intact.
Over time, repeated collisions removed the insulating mantles from their iron cores and then tore some of these cores to pieces.
Some of these pieces fell to Earth. The rocks that fell from space were of great interest to people and were a valuable resource in some cases; King Tut was buried with a dagger made of an iron meteorite, and the Inuit of Greenland made tools with an iron meteorite for centuries.
Scientists are very interested in iron meteorites for the information they contain.
A new study based on iron meteorites, which are fragments of the largest asteroid nucleus, examined isotopes of palladium, silver and platinum. By measuring the quantities of these isotopes, the authors could more narrowly restrict the timing of some events to the first solar system.
The paper “Dissipation of the Solar Nebula Restricted by Impacts and Cooling the Core in Planetary Animals” was published in Nature Astronomy. The lead author is Alison Hunt of ETH Zurich and the National Research Competence Center (NCCR) PlanetS.
“Previous scientific studies have shown that asteroids in the Solar System have remained relatively unchanged since their formation billions of years ago,” Hunt said. “They are, therefore, an archive in which the conditions of the first Solar System are preserved.”
The ancient Egyptians and Inuit knew nothing of the elements, isotopes, and decay chains, but we did. We understand how different elements degrade into chains on other elements and we know how long they take.
One of these decay chains is the focus of this work: the 107Pd-107Ag short-term decay system. This chain has an average lifespan of about 6.5 million years and is used to detect the presence of short-lived nuclides in the early solar system.
The researchers collected samples of 18 different iron meteorites that were previously part of the asteroid’s iron nuclei.
They then isolated palladium, silver and platinum and used a mass spectrometer to measure the concentrations of different isotopes of the three elements. A particular silver isotope is critical in this research.
During the first million years of the history of the Solar System, decaying radioactive isotopes warmed the metal nuclei of asteroids. As they cooled and more isotopes disintegrated, a silver isotope (107Ag) accumulated in the nuclei. The researchers measured the ratio of 107Ag to other isotopes and determined how quickly the asteroid nuclei cooled and when.
This is not the first time researchers have studied asteroids and isotopes in this way. But previous studies did not consider the effects of galactic cosmic rays (GCR) on isotope ratios.
GCRs can disrupt the neutron capture process during decay and can decrease the amount of 107Ag and 109Ag. These new results are corrected for GCR interference by also counting platinum isotopes.
“Our additional measurements of platinum isotope abundance allowed us to correct the silver isotope measurements for the distortions caused by the cosmic irradiation of the samples in space. So we were able to date the time of the collisions more accurately than ever, “Hunt said.
“And to our surprise, all the asteroid nuclei we examined had been exposed almost simultaneously, over a period of 7.8 to 11.7 million years after the formation of the Solar System,” he said. dir Hunt.
A time period of 4 million years is short in astronomy. During this brief period, all the asteroids measured had their nuclei exposed, meaning that collisions with other objects removed their mantle. Without the insulating mantles, all the cores cooled simultaneously.
Other studies have shown that cooling is fast, but they could not limit the time period so clearly.
For the asteroids to have the proportions of isotopes that the team found, the Solar System had to be a very chaotic place, with a period of frequent collisions that removed the asteroid’s mantles.
“It looks like everything was broken at the time,” Hunt says. “And we wanted to know why,” he adds.
Why would there be such a chaotic period of shocks? There are a couple of possibilities, according to the document.
The first possibility concerns the giant planets of the Solar System. If they migrated or were unstable in some way at that time, they could have reorganized the inner Solar System, disrupted small bodies like asteroids, and triggered a period of increased collisions. This scenario is called the Nice model.
The other possibility is the drag of gas into the solar nebula.
When the Sun was a protostar, it was surrounded by a cloud of gas and dust called a solar nebula, just like other stars. The disk contained asteroids, and eventually the planets would form as well. But the disk changed in the first million years of the Solar System.
At first, the gas was dense, which slowed the movement of things like asteroids and planetesimals with the drag of the gas. But as the sun went down, it produced more wind and solar radiation.
The solar nebula was still there, but the solar wind and radiation pushed it away, dissipating it. As it dissipated, it became less dense and there was less drag on the objects.
Without the cushioning effect of dense gas, asteroids accelerated and collided with each other more often.
According to Hunt and colleagues, the reduction in gas drag is responsible.
“The theory that best explained this initial energy phase of the solar system indicated that it was mainly caused by the dissipation of the so-called solar nebula,” said study co-author Maria Schönbächler.
“This solar nebula is the remnant of gas left of the cosmic cloud from which the Sun was born. For several million years, it still orbited the young Sun until it was swept away by solar winds and radiation.” , Schönbächler. dit.
“Our work illustrates how improvements in laboratory measurement techniques allow us to infer key processes that took place in the first solar system, such as the probable time the solar nebula had passed. Planets like Earth were still in process of being born in Ultimately, this can help us better understand how our own planets were born, but it will also give us an insight into others outside our solar system, ”Schönbächler concluded.
This article was originally published by Universe Today. Read the original article.