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Chondritic meteorites (chondrites) are some of the oldest rocks in our solar system, forming 4.5 billion years ago. Therefore, their primitive composition means that they offer a window into the origins of planet formation, particularly as their major elements (heavier than hydrogen and helium, including oxygen, silicon, magnesium, iron and nickel) closely reflect the sun's photosphere composition.

Melting and clumped accumulation (accretion) of dust particles at high temperatures (up to 2,000 Kelvin [~1,727 °C]) in the protoplanetary disk formed crystallized silicate spheres known as chondrules, which further joined together to produce asteroids, the remnants of planetary genesis.

There are two main types, believed to have formed in the inner and outer solar system respectively: ordinary chondrites are composed of up to 90% chondrules, while carbonaceous chondrites have only 20–50% chondrules within a background matrix.

Current knowledge has suggested that high energy collisions between space debris are required to deform and fragment chondrules to produce chondrites. However, research in Earth and Planetary Science Letters has suggested this may not be the case.

Instead, Professor Guy Libourel and Dr. Anthony Seret, of France's Laboratoire Lagrange at the Université Côte d'Azur, suggest that both plastic deformation and fragmentation of chondrules can occur at low collision velocities.

Explaining the importance of this research, Dr. Seret says, "While the understanding of meteorite formation and history has traditionally relied on chemical analysis, this study pioneers a mechanical approach, offering a fresh perspective on these celestial objects.

"Also, the principles of ductile deformation during hot collisions and self-cracking due to differential cooling could be extended to the study of other rocky bodies, including asteroids."

To investigate this further, the researchers used simulations to explore the mechanical behavior of chondrules during different temperature windows. Below a critical temperature threshold (the glass transition temperature), the chondrules behaved like a solid with brittle deformation and cracking, whereas above this the chondrules experienced ductile deformation and flowed like a viscous liquid.

More concretely, Professor Libourel and Dr. Seret note a particularly important finding: "At temperatures exceeding 1,000 Kelvin (~727 °C), cubic chondrule aggregates weighing just a few grams colliding at a relative velocity of less than 10 meters per second (with a kinetic energy of ≈ 40 millijoules) can induce the level of ductile, irreversible plastic deformation observed in meteorites.

"Conversely, below this critical temperature threshold, within a single isolate chondrule, differential thermal contraction between amorphous (shapeless) and crystalline silicate components can lead to spontaneous brittle cracking and even fragmentation, without requiring external impact."

The former scenario is most common in ordinary chondrites, while the latter occurs in the fragmented chondrules of carbonaceous chondrites.

"Ordinary chondrites formed through the accretion of numerous chondrules that were still hot and malleable, allowing them to deform and merge into a larger mass," Dr. Seret states.

"Carbonaceous chondrites formed from a smaller number of chondrules that cooled rapidly and became brittle, leading to spontaneous cracking before they could accrete. Therefore, this research underscores the delicate balance between ductility and brittleness in chondrite formation."