There is no doubt that young solar systems are messy places. Successive collisions defined our young solar system as repeatedly colliding rocks, rocks, and planets.
A new study based on fragments of asteroids that collided with Earth has laid out a timeline of some of that chaos.
Astronomers know that asteroids have remained essentially unchanged since they formed in the early solar system billions of years ago.
They are like rocky time capsules containing scientific evidence from that important era because distinct asteroids had mantles that protected their interiors from space weathering.
But not all asteroids remained intact.
Over time, repeated collisions stripped the insulating mantle of its iron core and then smashed some of these cores into pieces.
Some of these pieces fell to the ground. The rocks that fell from space were of great importance to people and were a valuable resource in some cases; King Tut was buried with a dagger made from an iron meteorite, and the Inuit people of Greenland made tools from an iron meteorite for centuries.
Scientists are very interested in iron meteorites because of the information they contain.
A new study based on iron meteorites – parts of the core of larger asteroids – looks at isotopes of palladium, silver and platinum. By measuring the quantities of these isotopes, the authors can constrain the timing of some events in the early solar system.
The research paper “Limiting Solar Nebula Dispersal to Impacts and Cooling of the Core in Minor Planets” was published in natural astronomy. Lead author is Alison Hunt of ETH Zurich and the National Center for Competence in Research (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 conditions of the early solar system are preserved.”
The ancient Egyptians and Inuit didn’t know anything about the elements, isotopes, and decay chains, but we do. We understand how different elements in chains decompose into other elements, and we know how long it takes.
One of those chains of decay lies at the heart of this work: short-lived 107Pd-107Ag decay system. This series has a half-life of about 6.5 million years and is used to detect the presence of short-lived nuclides from the early solar system.
The researchers collected samples from 18 different iron meteorites that were once part of the iron cores of asteroids.
Then they isolated palladium, silver and platinum and used a mass spectrometer to measure the concentrations of different isotopes of the three elements. The presence of a specific isotope of silver is critical in this research.
During the first millions of years of the solar system’s history, decaying radioactive isotopes heated metal cores in asteroids. As it cooled and more isotopes faded, an isotope of silver (107Ag) accumulated in the nuclei. The researchers measured the proportion of 107Ag to other isotopes and to determine how quickly and when the asteroid’s cores cooled.
This isn’t the first time researchers have studied asteroids and isotopes in this way. But previous studies did not take into account the effects of galactic cosmic rays (GCRs) on isotopic ratios.
GCRs can disrupt neutron capture during decay and can reduce the amount of 107Hajj and 109AG. These new results of GCR interference were corrected by calculating platinum isotopes as well.
“Our additional measurements of platinum isotope abundance allowed us to correct silver isotope measurements for distortions caused by cosmic irradiation of samples in space. So we were able to determine the timing of the collisions more accurately than ever before,” Hunt reported.
“To our surprise, almost all of the asteroid cores we examined were detected simultaneously, in a time frame of 7.8 to 11.7 million years after the formation of the solar system,” Hunt said.
A short 4 million year time period in astronomy. During that short period, the cores of all the asteroids that were measured were detected, which means that collisions with other objects have been stripped of their shells. Without the insulating jacket, the cores all cooled simultaneously.
Other studies showed that cooling was rapid, but they were unable to constrain the time frame clearly.
For asteroids to have the isotopic ratios the team found, the solar system would have to be a very chaotic place, with a period of frequent collisions that stripped the asteroid’s mantle.
“It seemed like everything was crashing together at the time,” Hunt says. “We wanted to know why,” she adds.
Why would there be a period of these chaotic collisions? There are several possibilities, according to the newspaper.
The first possibility concerns the giant planets of the solar system. If they migrated or were somehow unstable at the time, they could reorganize the inner solar system, disrupt small bodies such as asteroids, and cause a period of increased collisions. This scenario is called the NICE model.
Another possibility is gas clouds in the solar nebula.
When the Sun was a protostar, it was surrounded by a cloud of gas and dust called the solar nebula, just like other stars. The disk contained asteroids, and eventually planets would form there as well. But the disk changed in the first millions of years of the solar system.
At first, the gas was dense, which slowed the movement of things like asteroids and small planets as the gas clouds. But as the sun got older, it produced more wind and solar radiation.
The solar nebula was still there, but the solar wind and radiation pushed it to dissipate. As it dissipated, it became less dense, and there was less resistance to objects.
Without the damping effect of the dense gas, the asteroids accelerated and collided with each other repeatedly.
According to Hunt and her colleagues, reducing gas withdrawal is to blame.
“The theory that best explains this active early phase of the solar system suggests that the main cause is the dissipation of the so-called solar nebula,” explained study co-author Maria Schönbachler.
“This solar nebula is the remnant of gas left from the cosmic cloud from which the sun was born. For several million years, it was still orbiting the young sun until it was blown away by solar winds and radiation,” Schönbächler said.
“Our work demonstrates how improvements in laboratory measurement techniques allow us to infer key processes that occurred in the early Solar System – such as the likely time the solar nebula was gone. Planets like Earth were still in the process of being born at that time. Ultimately, it could help us This provides a better understanding of how our planets originated, but also gives us insight into others outside our solar system.”
This article was originally published by Universe Today. Read the original article.