A new method rewrites the age of asteroids

Salam, a moon of the Dinkinsh asteroid was discovered to be a "unique body known as a "pair in contact" and consists of two lobes that are actually piles of stones stuck together, and the first of its kind seen orbiting another asteroid

An asteroid discovered last November is actually a toddler in the solar system - only 2-3 million years old, estimates a research team led by Cornell University using innovative statistical calculations.

The team deduced the age of Selam, a "moon" orbiting the small asteroid Dinkinesh in the asteroid belt between Mars and Jupiter, based solely on dynamics, or how the pair moves through space. Their calculation matches that of NASA's Lucy mission based on analysis of craters on the asteroid's surface, the traditional method for dating asteroids.

The new method complements this work and has several advantages: it does not require an expensive spacecraft to take close-up images, it can be more accurate in cases where the surface of the asteroid has undergone recent changes, and it can be applied to the secondary bodies in dozens of other known binary systems, which make up 15% of the asteroids The country, the researchers said.

"Finding the age of asteroids is important to understanding them, and this asteroid is very young compared to the age of the solar system, meaning it formed fairly recently," said Colby Merrill, a doctoral student in aeronautics and space engineering. "Finding the age of this specific body can help us understand the entire population."

Merrill, a dynamics expert who was part of NASA's DART mission, watched intently as the Lucy spacecraft flew by Dinkinsh on November 1, 2023, and unexpectedly found Salam. Salam turned out to be an "unusually unique and complex body," Merrill said, known as a "couple in contact" and consisting of two lobes that are actually stacks of rocks stuck together, and the first of its kind seen orbiting another asteroid.

Binary asteroids are fascinating and dynamically complex objects involved in a tug-of-war, the researchers said. The gravity acting on the objects causes them to physically protrude and gyrations are formed, which slowly reduce the energy of the system. At the same time, the sun's radiation also changes the energy of the system through an effect called the binary ORP effect (BYORP). Eventually, the system will reach an equilibrium where the tides and BYORP are equally strong - stagnation in the tug of war.

Assuming these forces are in balance and with asteroid data shared by the Lucy mission, the researchers calculated how long it would have taken for Salaam to reach its current state after it was formed from material ejected from the rapidly spinning Dinkinsh surface. Along the way, the team said they improved existing equations that assumed the densities of the two bodies were equal and ignored the mass of the secondary body. After running about a million calculations with varying parameters, the result was that the median age of Salam is 3 million years, with the most likely result being 2 million.

The researchers hope to apply their new age determination method to other binary systems where the dynamics have been well characterized, even without close flybys.

"Used together with crater counting, this method will help to better constrain the age of a system," said PhD student Alexia Kovas, co-author of the paper. "If we use two methods, and there is a match between them, we can be more sure that we get a significant age that describes the current state of the system."

for the scientific article

More of the topic in Hayadan:

• The precious metal-rich asteroid 16 Psyche may not be a solid lump of metal after all but a pile of rocks
• A double asteroid - or two piles of stones?
• The Osiris Rex spacecraft successfully touched down on asteroid Benu in an attempt to obtain a sample