[meteorite-list] Earth Ejecta Could Have Seeded Life on Europa

[Ron Baalke]

http://www.technologyreview.com/blog/arxiv/27092/      

Earth Ejecta Could Have Seeded Life on Europa
Technology Review (MIT)
August 22, 2011

Life-carrying rocks ejected from Earth by asteroid impacts could have
made their way to Jupiter and beyond, say astronomers

Astronomers have long studied meteorites that have clearly come from the
Moon and Mars. These are the result of massive asteroid impacts which
eject material with such force that it ends up in interplanetary space,
eventually being washed up here.

This raises an interesting question: how much Earth ejecta could have
ended up elsewhere in the Solar System?

Various astronomers have studied this question by simulating how far
test particles can travel after being ejected from Earth. Their
conclusion is that it's relatively easy for bits of Earth to end up on
the Moon or Venus. But very little would get to Mars because it would
have to overcome both the Sun and the Earth's gravity.

Today, Mauricio Reyes-Ruiz at the Universidad Nacional Autonoma de
Mexico and a few pals reveal the results of the biggest simulation of
Earth ejecta ever undertaken. And they have a surprise.

These guys have created a computer model in which 10,242 test particles
are ejected from Earth into the Solar System. They've run the model five
times, increasing the average velocity of the ejected particles each time.

What they've found is quite a surprise. First up, the number of particle
that end up on Mars is two orders of magnitude greater than previous
studies have found.

But the biggie is that, at higher ejection speeds, particles are much
more likely to end up hitting Jupiter than Mars.

That could have significant implications for the possibility that life
on Earth could have travelled elsewhere. In these simulations, the
Mexican team followed the test particles for up to 30,000 years, which
is the length of time that astrobiologists believe Earth's hardiest
lifeforms might survive in space.

So that raises the possibility that Earth could have seeded life on
Jovian moons such as Europa, which many astronomers believe has a large
ocean. However, the Mexican team doesn't simulate the number of
particles that hit Jovian moons, only Jupiter itself.

Another surprise is that, at the higher ejection speeds, many particles
end up leaving the Solar System entirely. In fact, far more end up in
interstellar space than on all the planets combined, including those
that return to Earth.

If these particles can preserve life from Earth for even longer periods
than astrobiologists think, then at this very moment, life from Earth
could be speeding its way towards distant stars.

Ref: http://arxiv.org/abs/1108.3375 : Dynamics Of Escaping Earth Ejecta
And Their Collision Probability With Different Solar System Bodies