18 March, 2006

Titan seeded by life from Earth?

Sorry for yet another planetary geology post, but this is just cool. The BBC reports a presentation at the Lunar and Planetary Science Conference in Texas by Brett Gladman, from the University of British Columbia. He was interested in the ability of large meteorite impacts, such as the Chicxulub impact which may have killed off the dinosaurs, to eject rocks bearing microbial life into interplanetary space.

[Dr Gladman's team] calculated that about 600 million fragments from such an impact would escape from Earth into an orbit around the Sun. Some of these would have escape velocities such that they could get to Jupiter and Saturn in roughly a million years...

...[They] calculated that up to 20 terrestrial rocks from a large impact on Earth would reach Titan. These would strike Titan's upper atmosphere at 10-15 km/s. At this velocity, the cruise down to the surface might be comfortable enough for microbes to survive the journey.

But the news was more bleak for Europa. By contrast with the handful that hit Titan, about 100 terrestrial meteoroids hit the icy moon.

But Jupiter's gravity boosts their speed such that they strike Europa's surface at an average 25 km/s, with some hitting at 40 km/s. Dr Gladman said other scientists had investigated the survival of amino acids hitting a planetary surface at this speed and they were "not good".

Of course, just because it's possible for terrestrial life to be transferred to Titan doesn't make it likely. And although Titan is rich in organic compounds, it's still an extremely cold (getting on for -200 C) and harsh environment for any bacteria that did make it. An intriguing possibility though...

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