Space dust could carry alien life across the galaxy, study suggests

An artist's depiction of an asteroid hitting Earth.
Powerful asteroid impacts on life-harboring planets could eject small life-carrying particles into interstellar space, a March 2023 study suggests.. (Image credit: NASA/Don Davis)

Astrobiologists should examine space dust and other exoplanetary debris to search for the existence of life beyond Earth, a new study suggests.

Up to 100,000 pieces of life-carrying dust particles could be making their way to Earth every year, according to the study, which was authored by Tomonori Totani, an astronomy professor at the University of Tokyo. 

When a big asteroid slams into a planet, the impact can have cosmic repercussions — just ask the dinosaurs. (Or don't; they're extinct, killed off by a space rock that hit Earth 66 million years ago.) These cataclysmic collisions can create hemisphere-size craters and spread debris across entire planets and out into interstellar space. 

Related: The search for alien life (reference)

This piece of interplanetary dust is thought to be part of the early solar system and was found in Earth's atmosphere, demonstrating lightweight particles could survive atmospheric entry as they do not generate much heat from friction.

This piece of interplanetary dust is thought to be part of the early solar system and was found in Earth's atmosphere, demonstrating lightweight particles could survive atmospheric entry as they do not generate much heat from friction. (Image credit: NASA)

In the new paper, which was published online Wednesday (March 22) in the International Journal of Astrobiology, Totani argues that the debris ejected into space from a large enough impact on a life-inhabited planet could carry evidence of that life out into space with it.

Theoretically, fossilized microorganisms or other indications of life could be preserved on planetary ejecta as they careen away from their home planet, pending their survival through the harsh environment of outer space. Some of these debris particles could find their way to the surfaces of other life-sustaining planets, like Earth, where they could potentially establish a foothold — or, perhaps, be studied for evidence of alien life

This idea is similar in some respects to the panspermia hypothesis, which presumes life is ubiquitous and is proliferated throughout the galaxy from one planetary body to another. Totani cites this near the beginning of his paper, alongside the observation that Mars meteorites have been found here on Earth. "My paper explores this idea using available data on the different aspects of this scenario," Totani said in a press release

Not all debris from an exoplanet can be ejected with enough velocity that it not only escapes the gravity of its planet but also that planet's host star; rather, escapees must be tiny. Totani calculates that fragments around one micrometer (one one-thousandth of a millimeter) wide would be big enough to host something like a single-celled organism, and small enough to reach interstellar speeds. 

"The distances and times involved can be vast, and both reduce the chance any ejecta containing life signs from another world could even reach us," Totani said. "Add to that the number of phenomena in space that can destroy small objects due to heat or radiation, and the chances get even lower." 

Despite the odds, however, Totani's calculations show that up to 100,000 such pieces of space dust might possibly land on Earth each year, and may be present and well-preserved within Antarctic ice or on the seafloor. 

Those specimens may be relatively easy to recover, compared to space dust with evidence of microbial life still floating around in space. But that latter scenario isn't impossible either. 

"Discerning extrasolar material from material originating in our own solar system is still a complex matter," the press release states, but also points out that aerogel technologies that capture space dust exist today. 

Both the paper and the press release conclude with Totani urging scientists in adjacent fields to pick up this research and explore the possibilities it may add to the search for life outside our solar system. 

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Josh Dinner
Writer, Content Manager

Josh Dinner is's Content Manager. He is a writer and photographer with a passion for science and space exploration, and has been working the space beat since 2016. Josh has covered the evolution of NASA's commercial spaceflight partnerships, from early Dragon and Cygnus cargo missions to the ongoing development and launches of crewed missions from the Space Coast, as well as NASA science missions and more. He also enjoys building 1:144 scale models of rockets and human-flown spacecraft. Find some of Josh's launch photography on Instagram and his website, and follow him on Twitter, where he mostly posts in haiku.

  • Manix
    I am a big believer in Panspermia. I truly don't understand why this is such a controversial idea these days. The universe seems to be conditioned for life. There is apparently abundance of water throughout the universe and the building blocks of life seem to be contained in asteroids, meteors and comets. IF these rocks were to crash onto a world that could support or act as a catylist to life, why is this idea still seen as controversial? Clearly as we discover more this seems to be the most likely hypothesis of how life spread throughout the galaxy if not the universe.