Reverse pansperima: Chicxulub Impact Might Have Spread Life-Bearing Rocks Through the Solar System

Panspermia is the hypothesis that life exists throughout the universe, and is distributed naturally by meteoroids, asteroids, comets, and so on. Specifically, it states that life did not arise on Earth, but arrived here, from someplace else. (http://en.wikipedia.org/wiki/Panspermia)

Panspermia got a major theoretical boost in the last few decades, mostly after the Apollo missions to the moon: Once we had physical samples for comparison, a number of meteorite fragments, here on Earth, were conclusively proven to have come from the moon --- rocks blasted into space lunar impact events, and then falling to Earth.

Later, meteorites were similarly proven to have come from Mars, and asteroids. It turns out to be a fairly common process: Non-Earth stuff gets scattered into space, and lands here all the time.

Now, the reverse process has been shown to exist:

KentuckyFC writes"Some 65 million years ago, an asteroid the size of a small city hit the Yucatan Peninsula in what is now Mexico, devastating Earth and triggering the sequence of events that wiped out the dinosaurs. This impact ejected 70 billion kg of Earth rock into space. To carry life around the Solar System, astrobiologists say these rocks must have stayed cool, less than 100 degrees C, and must also be big, more than 3 metres in diameter to protect organisms from radiation in space. Now they have calculated that 20,000 kilograms of this Earth ejecta must have reached Europa, including at least one or two potentially life-bearing rocks. And they say similar amounts must have reached other water-rich moons such as Callisto and Titan. Their conclusion is that if we find life on the moons around Saturn and Jupiter, it could well date from the time of the dinosaurs (or indeed from other similar impacts)."http://classic.slashdot.org/story/13/11/18/1831250

So, the mechanism for panspermia exists; that part of the hypothesis is, er, rock solid, so to speak.

Of course, panspermia sidesteps the basic question of how life arose in the first place. It had to start somewhere, before it hitchhiked to other places on ejected rock fragments.

And panspermia doesn't address the idea that life may be an inevitable emergent property of the correct local conditions; not requiring lots of transport from place to place.

After all, we've only just started looking, and already have found something like 3,500 earthlike worlds in our immediate vicinity; and over 100 of those are in the habitable zone. Extrapolating the math suggests there are something like 40 billion earthlike worlds in our galaxy alone; one of countless hundreds of billions galaxies.

Given all that real estate, and the vastness of time, the idea that life arose only once, and only locally, seems kind of silly to me.

But still: Once life arises anywhere, it's looking entirely possible that it gets shuffled around, at least on an interplanetary scale, by catching rides on ejecta.

And that's kind of cool.