Asteroid strikes could seed solar system's life

The impact that doomed the dinosaurs may also have sent life to Jupiter, James Mitchell Crow reports.

Artist's impression of an asteroid near Earth

Sixty-five million years ago, a 10 km wide asteroid smashed into Earth dooming the dinosaurs to extinction. But elsewhere in the solar system it could have seeded life. That’s the prediction of computer models developed by a team at the Astrobiology Research Center at Penn State University.

The killer asteroid’s impact jettisoned hundreds of millions of tons of rocky debris into space – debris that harboured life. Safely cocooned inside the rock fragments, tough microbial spores could comfortably travel as far afield as Jupiter, says the new study by Rachel Worth Steinn Sigurdsson and Christopher House, published in the journal Astrobiology last December. Of particular interest, is that their models suggest about 20,000 kg of this material would have ended up on Jupiter's watery moon, Europa, long considered a candidate for harbouring life. Beneath its icy crust, the descendants of the hardy microbial space colonists might be living happily in the sheltered subsurface seas of Europa today.

The model also surprised the researchers by predicting that the ejected rock would reach Europa in less than 10 million years, much faster than they expected. “It turns out that the transfer is quite rapid,” says Sigurdsson.

The hardiest spores should survive for up to 30 million years – plenty of time for life to reach Europa, agrees physicist and astrobiologist Paul Davies from Arizona State University.

The main obstacle is what happens when the rock reaches Europa, he suspects. “The surface of Europa is a very unpleasant place.” But a lucky hit might see a rock fragment breach the planet’s very cold, dry surface by disappearing down a fissure in the ice to reach the subsurface ocean. The odds of a fragment reaching that watery oasis might sound slim. “But the solar system has been around for a long time and there is a lot of ejecta and you only need one viable microbe,” Davies says.

Ejected rock might have carried life to Europa but most of the rock launched into space would eventually have crashed back to Earth, the team showed. In the violent days of the early solar system, when asteroid collisions were common, a series of cataclysmic impacts might have wiped life from the planet only to re-seed it as ejected rock slowly rained back down onto the planet, something astrobiologists including Davies have previously suggested. “We showed explicitly that it is a very real possibility,” says Sigurdsson.

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