The impact has been blamed for the mass extinction of the dinosaurs, triggering volcanic eruptions and wildfires which choked the planet with smoke and dust.
It also launched about 70 billion kg of rock into space – 20,000kg of which could have reached Europa. And the chances that a rock big enough to harbour life arrived are “better than 50/50”, researchers estimate.
But could living organisms actually survive these epic trips?
“I’d be surprised if life hasn’t gotten to Mars,” Ms Worth told BBC News.
“It’s beyond the scope of our study. But it seems reasonable that at some point some Earth organisms have made it over there.”
But could life have survived there for any length of time is the next question.
As I noted in a recent article, many hypotheses about life on Mars are currently floating around, in various states of relationship with the evidence at any given time:
There was indeed water on Mars a long time ago there but then, we are told, a 600 million year drought ensued, so some now continue the search underground. Others look for life in the Martian pits. Or Mars’ volcanic glass. Still others search asteroid craters on Earth for clues to Mars “hiding life”. And some, impatient with Mars perhaps, hope to find life in undersea caves elsewhere in our solar system.
The asteroid impact theory has the advantage that we are not expecting bacteria to get started there independently, just survive there for some millions of years.