This rubber-like material, never before seen in space, likely formed in the early days of the solar system as the parent asteroid Bennu heated up. The ancient “space gum”, once soft and flexible but then hardened, is composed of polymer-like materials extremely rich in nitrogen and oxygen. Such complex molecules may have been the chemical precursors that helped give rise to life on Earth, and finding them in pristine Bennu samples is important for scientists studying how life began and whether it exists beyond our planet.
Electron microscopy of a particle from a sample from Bennu. Image credit: Sandford etc.., two: 10.1038/s41550-025-02694-5.
Bennu's progenitor asteroid was formed from materials from the Solar Nebula – the rotating cloud of gas and dust that gave rise to the Solar System – and contained many minerals and ices.
When the asteroid began to heat up due to natural radiation, a compound called carbamate was formed through a process involving ammonia and carbon dioxide.
The carbamate is soluble in water, but it survived long enough to polymerize, reacting with itself and other molecules to form larger, more complex chains that are impermeable to water.
This suggests that it formed before the parent body became hot enough to become aquatic.
“With this strange substance, we may well be seeing one of the earliest material changes that have occurred in this rock,” said Dr. Scott Sandford, a researcher at NASA Ames Research Center.
“On this primitive asteroid that formed at the dawn of the solar system, we are seeing events close to the beginning.”
In the study, the authors examined the characteristics of Bennu's rubber-like material.
As details emerged, evidence emerged that the material was deposited in layers on ice grains and minerals present in the asteroid.
It was also flexible—a pliable material similar to used rubber or even soft plastic.
Indeed, while working with the samples, the researchers noticed that the strange material bent and dimpled when pressure was applied.
The material was translucent, and exposure to radiation made it fragile, like a chaise longue left in the sun for too many seasons.
“Looking at its chemical composition, we see the same chemical groups that are found in polyurethane on Earth, making this material from Bennu something of a ‘space plastic,’” Dr Sandford said.
“However, the ancient asteroid material is not just polyurethane, which is an ordered polymer.”
“It has more random, mixed connections and an elemental composition that differs from particle to particle.”
teams conclusions were published on December 2, 2025 in the magazine Nature Astronomy.
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Yu.A. Sandford etc.. Organic material rich in nitrogen and oxygen indicates polymerization in pre-water cryochemistry on Bennu's parent body. Nat Astronpublished online December 2, 2025; doi: 10.1038/s41550-025-02694-5
