Ancient asteroids show early solar system was more chaotic than we thought


There is no doubt that chaos reigns in young solar systems. Cascading collisions defined our young solar system as rocks, boulders and planetesimals collided repeatedly.

A new study based on asteroid debris that crashed into Earth establishes a timeline for this chaos.

Astronomers know that asteroids have changed little since they formed in the early solar system billions of years ago.

They are like stone time capsules that contain scientific clues from that important era because differentiated asteroids had mantles. which protected their insides from cosmic weathering.

But not all asteroids remained intact.

Over time, repeated collisions ripped the insulating shells from their iron cores and then destroyed some of those cores. in pieces.

Some of these pieces fell to Earth. Rocks that fell from space were of great interest to humans and in some cases were a valuable resource; King Tutankhamun was buried with a dagger made from an iron meteorite, and the Inuit in Greenland have been making tools from an iron meteorite for centuries.

Scientists are very interested in iron meteorites because of the information they contain.

The new study, based on iron meteorites, which are fragments of the cores of larger asteroids, looked at isotopes of palladium, silver and platinum. By measuring the number of these isotopes, the authors were able to more accurately determine the timing of some events in the early solar system.

The article “Dispersion of the solar nebula constrained by collisions and cooling of the core of planetesimals” was published in the journal Nature Astronomy . The lead author is Alison Hunt of ETH Zurich and the National Center for Scientific Research (NCCR) PlanetS.

“Previous scientific studies have shown that asteroids in the solar system have changed little since they formed, billions of years ago,” Hunt said. “They therefore represent an archive that preserves the conditions of the early solar system.”

The ancient Egyptians and Inuit knew nothing about elements, isotopes and decay chains, but we do. We understand how different elements break down into other elements in chains, and we know how long it takes.

This work is based on one of these decay chains: the short-lived 107 sup>Pd– 107 Ag decay system. This chain 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 parts. iron cores of asteroids.

They then isolated palladium, silver and platinum from them and measured the concentrations of various isotopes of the three elements using a mass spectrometer. The specific isotope of silver is critical in this study.

During the first few million years of the solar system’s history, decaying radioactive isotopes heated the metallic cores of asteroids. As they cooled and more isotopes decayed, the silver isotope ( 107 Ag) accumulated in the nuclei. The researchers measured the ratio of 107 Ag to other isotopes and determined how quickly and when the asteroid cores cooled.

This is not the first time researchers have studied asteroids and isotopes in this way. But earlier studies did not take into account the influence of galactic cosmic rays (GCR) on the isotope ratio.

GCRs can disturb the process of neutron capture during decay and reduce the amount of 107 sup>Ag and 109 Ag. These new results are corrected for GCR interference by counting platinum isotopes.

“Our additional platinum isotope measurements allowed us to correct silver isotope measurements for distortions caused by cosmic irradiation of samples in space. So we were able to date the collisions more accurately than ever before,” Hunt said.

“And, to our surprise, all of the asteroid nuclei we examined were detected almost simultaneously, within a 7.8 time frame. up to 11.7 million years after the formation of the solar system,” Hunt said.

The span of 4 million years is short for astronomy. During this short period, all of the measured asteroids had their cores exposed, meaning that collisions with other objects tore off their mantles. Without insulating mantles, all cores cooled simultaneously.

Other studies have shown that the cooling was rapid, but they could not limit the time frame as clearly.

To asteroids Judging by the isotope ratios found by the team, the solar system must have been a very chaotic place with a period of frequent collisions that ripped the mantles off asteroids.

“Everything seemed to come together at the time,” Hunt says. “And we wanted to know why,” she adds.

Why was there a period of such chaotic clashes? According to the article, there are several possibilities.

The first possibility concerns the giant planets of the solar system. If they migrated or were somehow unstable at the time, they could have reorganized the inner solar system, destroyed small bodies like asteroids, and triggered a period of increased collisions. This scenario is called the Nice model.

Another possibility is gas drag in the solar nebula.

When the Sun was a protostar, it was surrounded by a cloud of gas and dust. called the solar nebula, like other stars. The disk contained asteroids, and planets eventually formed there as well. But the disk has changed in the first few million years of the existence of the solar system.

At first, the gas was dense, which slowed down the movement of asteroids and planetesimals due to gas drag. But as the Sun accelerated, it produced more solar wind and radiation.

The solar nebula was still there, but the solar wind and radiation pressed against it, dispersing it. As it dissipated, it became less dense and objects offered less resistance.

Without the dampening effect of the dense gas, the asteroids accelerated and collided with each other more frequently.

According to the data, Hunt and her colleagues believe that the reason for this is a decrease in gas drag.

“The theory that best explained this energetic early phase of the solar system indicated that it was caused primarily by the scattering of the so-called solar nebula,” said study co-author Maria Schönbakhler.

“This solar nebula is the remnant of gas left over from the cosmic cloud from which the Sun was born. For several million years, they still revolved around the young Sun until it was blown away by the solar wind and radiation,” Schoenbechler said.

“Our work illustrates how improvements in laboratory measurement methods allow us to draw conclusions about key processes that occurred during the early solar periods. systems – for example, the probable time for which the solar nebula disappeared.

Planets like Earth are still in the process of birth at that time. Ultimately, this could help us better understand how our own planets began, as well as give us insight into others outside our solar system,” Schoenbachler concluded.


Contact us: [email protected]

Our Standards, Terms of Use: Standard Terms And Conditions.