One of space science’s longest-standing puzzles may finally have an answer. Scientists say they’ve figured out why carbon-rich asteroids – which are common in space – almost never make it to Earth’s surface.
The findings, published in the journal Nature Astronomy, could reshape our understanding of how the Solar System formed, and how the ingredients for life first arrived on Earth.
Carbon-rich asteroids are everywhere in the Solar System. According to existing models, they should account for about half of all meteorites that hit the ground.
But in reality, they make up just 4 per cent of recovered meteorites – a discrepancy that has baffled scientists for decades.
The new study suggests these missing space rocks may be breaking down before they ever reach our atmosphere – worn away by repeated heating as they pass close to the Sun.
“We’ve long suspected weak, carbonaceous material doesn’t survive atmospheric entry,” said Dr Hadrien Devillepoix, a researcher from Curtin University’s School of Earth and Planetary Sciences and co-author of the new study.
“What this research shows is many of these meteoroids don’t even make it that far: they break apart from being heated repeatedly as they pass close to the Sun.
The study analysed 7,982 meteoroid trajectories and 540 potential meteorite falls, identifying a pattern: asteroids made of carbon-rich material are far more likely to disintegrate in space, especially after repeated close passes to the Sun.
The few that do survive the journey are also more likely to make it through our atmosphere intact.
This has big implications for our understanding of life’s origins. Although rare on Earth, carbon-rich meteorites are chemically important.
Paris Observatory’s Dr Patrick Shober, who led the study, added, “Carbon-rich meteorites are some of the most chemically primitive materials we can study – they contain water, organic molecules and even amino acids.
“However, we have so few of them in our meteorite collections that we risk having an incomplete picture of what’s actually out there in space and how the building blocks of life arrived on Earth.”
Understanding what gets filtered out and why, Shober said, could help scientists reconstruct the Solar System’s early history and refine our theories of how Earth became habitable.
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