AND PERHAPS LIFE CAME TO EARTH THE SAME WAY, FROM MARS: The Amazing Trajectories of Life-Bearing Meteorites From Earth.

About 65 million years ago, the Earth was struck by an asteroid some 10 km in diameter with a mass of well over a trillion tonnes. We now know the immediate impact of this event–megatsunamis, global wildfires ignited by giant clouds of superheated ash and, of course, the mass extinction of land-based life on Earth.

But in recent years, astrobiologists have begun to study a less well known consequence: the ejection of billions of tonnes of life-bearing rocks and water into space. By some estimates, the impact could have ejected as much mass as the asteroid itself.

The question that fascinates them is what happened to all this stuff.

Today, we get an answer from Tetsuya Hara and buddies at Kyoto Sangyo University in Japan. These guys say a surprisingly large amount of Earth could have ended up not just on the Moon and Mars, as might be expected, but much further afield.

In particular, they calculate how much would have ended up in other places that seem compatible for life: the Jovian moon Europe, the Saturnian moon Enceladus and Earth-like exoplanets orbiting other stars.

Somewhere, Fred Hoyle is smiling.