Earthly bacteria could have reached distant planets and moons after being flung into space by massive meteorite impacts, scientists suggest. The proposal neatly reverses the panspermia theory, which suggests that life on Earth was seeded by microbes on comets or meteorites from elsewhere. Both theories envision life spreading through the Solar System in much the same way that germs race around a crowded classroom, says Jeff Moore, a planetary scientist at NASA's Ames Research Center in Moffett Field, California. "Once one planet comes down with life, they all get it."Impacts on Mars and the Moon are known to throw rocks into space that end up on Earth as small meteorites. But spraying Earth rocks towards the edges of the Solar System is more difficult, because the material has to move away from the Sun's strong gravity.To find out just how many rocks could reach the outer Solar System, a team of scientists used a computer model to track millions of fragments ejected by a simulated massive impact, such as the one that created the Chicxulub crater some 65 million years ago.

Similar sized events are thought to have happened a few times in Earth's history.The researchers looked in part at how many Earthly fragments would reach environments thought to be relatively well suited to life, such as Saturn's moon Titan and Jupiter's moon Europa. "I assumed the answer would be very, very few," says Brett Gladman, a planetary scientist at the University of British Columbia, Vancouver, Canada, who led the team. But Gladman was surprised to find that within 5 million years, about 100 objects would hit Europa, while Titan gets roughly 30 hits. He presented the results at the Lunar and Planetary Science Conference in League City, Texas, on 16 March.

View: Full Article | Source: Nature.com

This could mean humans might exist in other planets because of us
A comet hit earth 1000's of years ago and some human dna/bacteria traveled to a distant planet?

I don't think it works that way, only microbial life can survive in space. If a meteorite lands on another planet with life on it evolution pretty much starts all over again.

Oh crap, that means if we finally find life on other planets in the solar system, the religious fanatics are not going to be convinced.

Convinced of what? If it is that you want them to understand evolution, you have only to make your own lifeforms and then cause them to evolve at an accelerated rate for observation to prove it takes place under varying conditions.

It would be great if maybe and a big maybe but to find say for example a sea sponge on titan would be huge, ok I'll settle for a few plankton but damn any life is good life.

Unless the life you find wants to eat you!

If it was that easy!
Even then there will be fundies that still would not believe.

Interesting theory. Too bad it can't be proven to be true. I personally don't believe
that microbes would survive the impact let alone the journey through the vacuum
of space. After all the microbes from Mars found in Antarctica were fossilized.
Not to mention the fact that life from Earth can't survive in the harsh environments
of Titan or Europa.

That's not true, microorganisims are the most primitive creatures on our planet. They're the first organisims to had exist. 100 million years ago, they could of been a lot EVEN more primitive. By saying this, they'd need less of the more carbon based requirements that we need. I'm sure that more earlier micro organisims could of survived space.

+ how roaches can withstand tremendous radiation and extreme cold.

Actually even the most primitive life on earth was carbon based, the very DNA on which all earth based life is based is a carbon based chemical.

By 100 million years ago life on earth was very advanced, this is the period of the dinosaurs. Micro-organisms have not changed much since then.

The most primitive life on earth dates back to more than 3 BILLION years ago.

Bacteria have been known to survive the harsh environment of space. Living bacteria were found on parts of the Surveyor 3 un-manned lunar lander returned to earth by Apollo 12 and on the the Long Duration Exposure Facility (LDEF) which was placed into orbit by the shuttle in 1984 and returned in 1990. However their is a big difference between 6½ years and the 5 million years the scientists are talking about.

The Guinness Book Of Records says that the oldest surviving bacteria were found in salt crystals. They were in a kind of suspended animation but were revived by scientists. They were 250 million years old.

Despite the fact that is possible I personally doubt that life has been transferred from Earth to Europa or Titan this way. First of all we have the 130 rocks that will have hit these worlds. This is just a statistical number based on computer simulations. The scientists will almost certainly have made a few assumptions to get these figures so we can not be sure exactly how accurate they are.

Secondly even if their calculations are 100% the figure they have generated is a statistical probability. The motion of small objects through the solar system is chaotic. Over long periods of time it is impossible to predict their motion. It is, therefore, possible that in reality 260 earth meteorites hit these worlds or none at all.

Thirdly, even though bacteria 250 million years old survived on earth they needed particular conditions. I don't know how common these conditions are but I'd bet my house that considerably less than 1% of rocks will produce these conditions. Even if the figure is as high as 1% that means only 1 of these rocks would have the conditions for the bacteria to survive.

Next we have the blast itself. The bacteria need to survive the impact blast and intense heat generated at the moment that the impact body collided with earth.

After surviving their traumatic launch and millions of years in space things are going to get worse for these bacteria. They are going to hit either Europa or Titan. Europa has no atmosphere so the rock containing the bacteria is not going to be slowed down. It will impact Europa at tens of thousands of miles an hour. This means there will be a high energy impact which the bacteria must survive. Titan has a thick atmosphere. The rock will be slowed down by it's plunge through Titans atmosphere so it will not hit the ground so fast, however the rock will be heated and partly burned up by the atmospheric atmosphere.

If the bacteria have survived all this they must be luck enough to find an environment they can survive in. On Europa it is hypothesised that there are geothermal vents which provide the heat where life could survive. If the rock were to just sit on the surface or plunge into the ocean at a point where there are no geothermal vents it seems unlikely to me that it will be able to find the energy required for it to survive and reproduce. Titan is very cold. It also has an atmosphere more like the earth had billions of years ago rather than that in which life has become abundant. Unless the conditions are right, again the bacteria will not be able to reproduce.

The study in the initial article shows that it is possible that Earth seeded the solar system with life, it didn't show that it was likely.

Even a roach can't survived 5 million years in space.

These bacteria could survive on another planet. In an Earth lab, Deinococcus radiodurans (D. rad) survive extreme levels of radiation, extreme temperatures, dehydration, and exposure to genotoxic chemicals. Amazingly, they even have the ability to repair their own DNA, usually with 48 hours.

Known as an extremophile, bacteria such as D. rad are of interest to NASA partly because they might be adaptable to help human astronauts survive on other worlds. A recent map of D. rad's DNA might allow biologists to augment their survival skills with the ability to produce medicine, clean water, and oxygen.

Already they have been genetically engineered to help clean up spills of toxic mercury. Likely one of the oldest surviving life forms, D. rad was discovered by accident in the 1950s when scientists investigating food preservation techniques could not easily kill it.

D. rad Bacteria: Candidate Astronauts

The problem is that most bacteria are not extremophiles. If extremophiles were on the pieces of rock blasted off of the earth then there is a chance that they could survive the journey and survive on another world, however the vast majority of bacteria are killed at relatively low temperatures, that is why we cook food.

Apollo 12 astronauts retrieved parts from the lunar probe Surveyor 3 for analysis. A common bacteria, Streptococcus mitis, was unintentionally present inside the spacecraft's camera at launch. Around 50 to 100 of these bacteria survived dormant in this harsh environment for three years, to be detected when Apollo 12 brought the camera back to Earth. Many bacteria have dormant forms which can survive in harsh environments, and merely being dormant is not sufficient to make an organism be considered an extremophile.

Extremophile

ps I find this interesting since some believe we didn't go to the moon...

The bacteria found in Surveyor 3 were inside the camera and hence partially protected from the harsh environment of space. They were not blasted onto the moon as the result of a huge impact on the earth but gently placed there. There is a vast difference between 3 years (some bacteria survived 6 years in earth orbit on NASA's LDEF but this does not prove they could survive the hundreds of thousands or millions of years needed to seed another world.

I will emphasise what I have said in all my posts, I don't think this process is impossible just very VERY improbable.