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
