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Earth Space Science

Scientists Study Trajectories of Life-Bearing Earth Meteorites 199

Hugh Pickens writes "About 65 million years ago, Earth was struck by an asteroid some 10 km in diameter with a mass of well over a trillion tonnes that created megatsunamis, global wildfires ignited by giant clouds of superheated ash, and the mass extinction of land-based life on Earth. Now astrobiologists have begun to study a less well known consequence: the ejection of billions of tons of life-bearing rocks and water into space that has made its way not just to other planets but other solar systems as well. Calculations by Tetsuya Hara and his colleagues at Kyoto Sangyo University in Japan show that a surprisingly large amount of life-bearing material ended up not on the Moon and Mars, as might be expected, but the Jovian moon Europa and the Saturnian moon Enceladus also received tons of life-bearing rock from earth. Even more amazingly, calculations suggest that most Earth ejecta ended up in interstellar space and some has probably already arrived at Earth-like exoplanets orbiting other stars. Hara estimates that about a thousand Earth-rocks from this event would have made the trip to Gliese 581, a red dwarf some 20 light years away that is thought to have a super-Earth orbiting at the edge of the habitable zone, taking about a million years to reach its destination. Of course, nobody knows if microbes can survive that kind of journey or even the shorter trips to Europa and Enceladus. But Hara says that if microbes can survive that kind of journey, they ought to flourish on a super-Earth in the habitable zone (PDF). 'If we consider the possibility that the fragmented ejecta (smaller than 1cm) are accreted to comets and other icy bodies, then buried fertile material could make the interstellar journey throughout the Galaxy,' writes Hara. 'Under these circumstances fragments could continue the interstellar journey and Earth origin meteorites could be transferred to Gl 581 system. If we take it as viable, we should consider the panspermia theories more seriously.'"
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Scientists Study Trajectories of Life-Bearing Earth Meteorites

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  • Place Bets Here (Score:3, Interesting)

    by flyneye ( 84093 ) on Thursday April 12, 2012 @08:27AM (#39656175) Homepage

    Hmmm, made it to other Earth-like planets instead of randomly catching a closer strong gravitational field or drifting randomly into nothingness.
    Even making Europa would be kind of like hitting a cockroach with a needle from across a football stadium.
    Oh to be the house, if this scientist ever landed in Vegas with a wallet-load... Sounds like someone needs to re-fill the ol' grant jar.

  • Sub 1cm Ejecta (Score:5, Interesting)

    by RivenAleem ( 1590553 ) on Thursday April 12, 2012 @08:27AM (#39656177)

    How do objects this size survive the trip through the destination planet's atmosphere?

  • by Trapezium Artist ( 919330 ) on Thursday April 12, 2012 @08:30AM (#39656205)

    I've made a quick scan of the underlying academic article by Hara et al., along with one of my colleagues in a meeting here, who is closely involved in the issue of planetary protection (i.e. making sure that our spacecraft don't "pollute" the solar system bodies they fly to and land on).

    Of course, this is a known issue in general: after all, there are meteorites on Earth which we know came from Mars, so the converse is obviously possible. But extending this to moons of Jupiter, Kuiper Belt objects, and even exoplanetary systems, and finding that a significant number of Earth rocks may have been dumped there is interesting. So, the article is worth a more careful read.

    However, my antennae were sent into a state of high agitation when I saw that the article has been posted on the arXiV following its having been accepted to the infamous Journal of Cosmology. We've discussed that here before: I invite you to view the journal website (easily found by googling) and decide for yourselves how reputable it is.

    Which raises the question of why Hara et al. chose to publish there. That I can't answer, obviously, but will keep it firmly in mind as I read the paper in more detail.

  • Re:Panspermia (Score:5, Interesting)

    by fatphil ( 181876 ) on Thursday April 12, 2012 @08:41AM (#39656261) Homepage
    I've seen arguments on a scientific mailing list in the last few days that this paper is based on false assumptions. It has assumed (too high) values for masses based on (too low) values for velocities based on the assuption that the meteorites are aiming at earth under its gravity, rather than aiming for the sun under its gravity and accidentally hitting earth on its way towards the sun.

    If you change the masses downwards to what they should be, then the chance of them getting through an atmosphere without breaking/burning up and denaturing all its alleged payload become minuscule.
  • Re:Panspermia (Score:5, Interesting)

    by Migraineman ( 632203 ) on Thursday April 12, 2012 @09:33AM (#39656737)

    I guess he just threw a rock to see what would happen at some point.

    So your version of God isn't all-knowing and all-powerful? I'm not buying that a God who is capable of creating billions of planets, stars, and systems wouldn't have a firm grasp on probability and interstellar trajectories. Maybe we should consider that your God is bored (he does control everything, right?) and has set up the universe as a giant Rube Goldberg machine for His entertainment. He would have to accede to non-interference for the exercise to have any value.

  • by Lluc ( 703772 ) on Thursday April 12, 2012 @10:25AM (#39657429)
    Assume we're just dealing with Carbon (molecular weight 12) here, and "well over 1 trillion tonnes" is actually 2 trillion tonnes:

    number of molecules per gram = (Avogadro's Number) / 12 grams = 5.02E25 molecules/kg
    2 trillion tonnes = 2E15 kg
    (5.02E25 molecules / kg * 2E15 kg) = 1.004E41 molecules

    Surface area of sphere with radius of 20 light years = 4.499E35 meters^2

    1.004E41 molecules / 4.499 meters^2 = 223,091 molecules / meter^2 == 4.44 attograms of carbon per square meter.
    This is a pretty thin layer of material to survive reentry on some 20 light year distant planet.

    Alternatively, from google: ((Avogadro's number / (12 grams)) * (2 trillion tonnes)) / (4 * pi * ((20 lightyears)^2)) = 0.223099739 kilometers per liter = 0.5 miles/US gallon, which means we totally need to collect some gas guzzler tax on this material
  • by onyxruby ( 118189 ) <> on Thursday April 12, 2012 @01:31PM (#39660727)

    Just a thought here, but I don't think re-entry would be that challenging for bacteria based life to survive. Most people think that what left of an asteroid is really hot when they land, but that just isn't the case. In fact asteroids have been touched right after landing and described as 'cool' in temperature. []

    If bacteria were in the core part of the asteroid that survived impact it should be reasonable to assume that the part that is cool to the touch never got hot enough to kill any bacteria that were inside it. The other two questions than become what kind of shock (g-forces) can bacteria survive? We know they can survive the shock of being launched into space, and without the squishy bodies that we have they may well survive the shock of re-entry.

    If we could determine the answers to those questions than really the only questions remaining are can bacteria adapt to their new home? We already know they live in places on earth that are very inhospitable by our standards. The only other real question is how long can they survive in space? We have documented cases of bacteria surviving in space for years at a time. If there is no real limit to how long they can survive in space than cross solar system colonization is all but inevitable.

Anyone who imagines that all fruits ripen at the same time as the strawberries, knows nothing about grapes. -- Philippus Paracelsus