Professor Martin McCoustra of Heriot-Watt University, working with colleagues in Germany, Japan, the USA and Spain, helped compile decades of observational, laboratory and modelling studies. Their conclusion: space dust is often riddled with voids, increasing surface area dramatically and influencing how molecules form and evolve in space.
"In fact, they're more like fluffy little sponges, riddled with tiny voids," said McCoustra. His work on the review was supported by the UK Engineering and Physical Sciences Research Council.
Dust grains shape the universe by providing surfaces for chemical reactions in star-forming regions such as the Pillars of Creation. They also influence how starlight passes through clouds of gas and dust. Dr Alexey Potapov of Friedrich Schiller University Jena, the review's lead author, said: "If these grains are porous, that means they have a far greater surface area than we thought. That could radically change our understanding of how molecules form and evolve in space."
The study drew on multiple space missions. NASA's Stardust spacecraft recovered porous comet particles, while ESA's Rosetta mission to comet 67P found fragile dust with porosities exceeding 99 percent. Analyses of interplanetary dust particles collected on Earth show similar results.
Porosity may help grains clump together during the first stages of planet formation and provide sheltered sites for water and organic molecules to form. However, their fragility also makes them vulnerable to destruction by shocks and radiation during interstellar journeys.
Despite the evidence, astronomers remain divided. Some models suggest highly porous dust would be too cold or fragile to fit observations of interstellar clouds and young planetary systems. "We should remember that nearly 100 years ago, astronomers did not believe molecules could exist in space, as the environment was considered too harsh," McCoustra said. "Today, astrochemistry is recognised as addressing fundamental questions in terms of star formation and the origins of life."
The authors conclude that more laboratory work, observations and advanced modelling will be needed to settle the debate.
Related Links
Heriot-Watt University
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