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There’s Something in the Air: Trans-planetary Microbes

The views expressed are those of the author and are not necessarily those of Scientific American.

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Here come the microbes! (Credit: China Foto Press/Barcroft Medi)

Cover your mouth when you cough!

We’ve all learned the hard way that microbial organisms, from bacteria to viruses, can be transported by air. But the extent to which organisms exist in the Earth’s atmosphere is only now becoming clear.

There is good evidence that bacteria (or bacterial spores) can help nucleate water condensation, seeding clouds and encouraging precipitation. It has been speculated that this could even form part of a bacterial life-cycle, lofting organisms into the air, transporting them, and bringing them back to earth for fresh pastures.

There’s also growing evidence for just how widespread airborne microbial ‘ecosystems’ might be. Scientists in Austria have found bacteria in cloud droplets at 10,000 feet as well as clear signs that these microbes are not just passengers – they’re actually growing and reproducing in-situ in the super-cooled water environment. This suggests that clouds are quite literally another habitat for life on Earth, and with an average covering of 60% of the planetary surface represent a pretty major ecosystem.

Now a new study finds that dust plumes in the troposphere are carrying over 2,000 distinct species from Asia to North America – right across the Pacific Ocean. Some of these organisms are fungal, but at least 50% are bacterial, and make the trans-planetary journey in only 7-10 days when storms loft them as high at ten miles into the atmosphere.

This might not seem so surprising, we know that single-celled organisms occupy almost every niche on the planet. However, it does seem that the Asian microbes represent a distinct population that’s usually only a trace on the continental USA – but when the wind blows their numbers on the western hemisphere definitely increase significantly. This means that there is real mixing of species going on, a microbial pollution that may have consequences for all manner of things, including local ecosystem function and even disease.

Now *that's* a dust storm. Before and after images of Mars, dust blankets the planet on the right (Credit: NASA/STScI Hubble imagery)

It’s fascinating stuff. This kind of transportation must have been going on across all three to four billion years of life on Earth, leading us to wonder exactly what role it may have played in maintaining the global biosphere. It’s also food for thought in considering the potential ecosystems of Mars, a place where planet-wide dust storms regularly loft particles high into the atmosphere.


Caleb A. Scharf About the Author: Caleb Scharf is the director of Columbia University's multidisciplinary Astrobiology Center. He has worked in the fields of observational cosmology, X-ray astronomy, and more recently exoplanetary science. His books include Gravity's Engines (2012) and The Copernicus Complex (2014) (both from Scientific American / Farrar, Straus and Giroux.) Follow on Twitter @caleb_scharf.

The views expressed are those of the author and are not necessarily those of Scientific American.

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  1. 1. Fossilnut 11:40 am 12/18/2012

    Interesting stuff. Ecosystems afloat on airways.

    Why the last statement about Mars? There’s some inate need at SciAm to go off the rails with speculation. The science of the findings are fascinating in themselves.

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  2. 2. caleb_scharf 12:08 pm 12/18/2012

    It’s not an innate need of Scientific American, it’s my innate need as a working scientist to pose what I think are interesting, albeit speculative, questions. Part of what this blog does (given it’s theme of exoplanetary science and astrobiology) is to air ideas and explore connections.

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  3. 3. Torbjörn Larsson, OM 1:41 pm 12/18/2012

    It is certainly a good potential pathway to avoid huge impact rate conditions by increasing dispersal. But I have to wonder how high survivability was before our atmosphere oxygenation and its protective ozone layer, re heavy bombardment and psychrophile martian worlds.

    “Scientists in Austria have found bacteria in cloud droplets at 10,000 feet as well as clear signs that these microbes are not just passengers – they’re actually growing and reproducing in-situ in the super-cooled water environment.”

    Again, I find the study intriguing if not compelling. (And I believe the astrobiologists agree, isn’t this, a putative high altitude ecosystem, a controversial area?)

    For one, I don’t see that they check for sporulation or encystment either initially or at low temperatures, but instead extrapolate growth to supercooled water temperatures. [ ]

    Sporulation would also couple back to early worlds, one can’t expect to find it before DNA and its regulated cell division mechanisms has evolved. In our case spores appears with bacteria so after archaea diverged. [ ] Encystment seems an easier if not as sturdy complement tough. [ ]

    Nevertheless, the area is highly interesting. Thanks for being on top of this lofty subject!

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  4. 4. Torbjörn Larsson, OM 1:44 pm 12/18/2012

    Maybe I should say “survive high impact rate conditions” rather. You can’t avoid it, and survival is the name of the game anyway.

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  5. 5. dadster 9:07 am 12/19/2012

    This is pretty old stuff ..
    Yet humans think that planet earth is made for them .
    Humans are such an insignificant component of the total life system on the planet , except for humans !
    Microbes, single – celled organisms that they are , are not only surviving by their “wits” overcoming as many wide and varied obstacles as multicellular organisms like humans do with equal or more success in combating environmental hazards to survive and carry on for billions of years on planet earth co- existing with humans and all other life forms on earth but also perhaps more successful in interplanetary travels than humans .
    And, perhaps they would have long back quit planet earth and the solar system itself, before getting fried with humans when our sun start eating up the planets in the solar system , in its “red giant” avatar in a few billion years more.

    They ought to make us feel humble , if not leave us humiliated !
    They seem to be the quintessence of “life” whereas we the overgrown cancerous growth of life-cells predating on all other life forms and over- using the resources of planet earth greedily steeped in our overwhelming hubris.

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  6. 6. vinodkumarsehgal 9:53 am 12/19/2012

    planetary atmosphere may be limited up to few miles above the surface of planets. Within large distance running into million of miles between planets, there may be either absence of any atmospheric air/gas or it may be very sparse. In such case, how microbial life forms — bacteria or viruses may transport from one planet to another within our solar system?

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  7. 7. dadster 11:29 am 12/19/2012

    In continuation to my previous comments i have this much to add .

    Of course ,we are not microbes ,  we are human beings with our own egos hubris , emotions , sentiments , which microbes are not endowed with . We live our life satisfying our  greed and other weaknesses and strengths . Many of our strengths are our weaknesses too. They have only their instinct of survival to take care of and to guide them .

    But,  We are endowed with ” free will ” which is a double edged sword , which we are just mastering to use for our survival in cosmos in an ” informed” way, not getting buffeted by  random chance as microbes and other mono- cellular organisms are subjected to. Since homo sapiens are evolutionary refinements on microbes ( or so we want to think of ourselves ) and, since  the characteristic defining quality of “life”  is survival,what qualities we are blessed with,ought to prove  logically to be  better survival tools of which we ought to be proud of !
    Isn’t it ? We should feel superior to microbes in every way ! ( is this our hubris again raising its evil head ? We hope , we are  not doing  that ) . We hope it’s a  redeeming fact that we are stating . In computer terminology , we the complex multicellular organisms  are to be considered as   the “sophisticated advanced software” of nature and,  the organic single celled micro- organisms infused with life- energy are to be considered as the “raw initial elementary software” products of nature  . This reduces the electromagnetic energy -products ( both in its  radiating-energy form and the lumpen matter-energy form),  as the
    hardware of nature that provides the structure for life- energy to manifest.

    This brings us to reconsider the proposition of “élan vital”,  which got discredited somewhere on the way , like it happened with the ” cosmological constant ” ( which incidentally is revived now ).

    Analogically , we can say that microbiology is to life- sciences as nano technology ( or quantum science)  is to material physics. Microbes help us  to re- establish the fact that ” life” is not an emergent phenomena but as fundamental ( if not more fundamental ) an entity as matter is, in cosmos. Matter is the medium  through which   life-energy  manifests in our three dimensional material world just like light needs matter to manifest itself as otherwise we cannot “see” or sense light energy.

    The differences between life- energy and matter- based energies are too stark to ignore . Life- energy is an organizing energy unlike matter- energy which is a disintegrating , dissipating type of energy subject to entropy . Matter- energy tend to arrive at stabilized states . Life- energy is basically de- stabilizing, lively and dynamic .Life-energy is endowed with the defining quality of possessing “instinct of survival” which matter- based energy lacks . Awareness of environments , instinct of self- propagation, etc are manifestations of the instinct of survival.

    To go one step further.
    The recent Cambridge university proposal expressed in the  ” pandora’s box ” article proposes that the most fundamental entity in the cosmos is NOT, quarks, strings , protons or electrons but it is ” INFORMATION ” .

    Bytes and bits  of Information is life- based phenomenon not fundamentally matter- based which makes “matter” as the emergent phenomena and, “life- energy ” the fundamental entity out of which matter emerges . Spontaneous manifestation of “life-energy”  emanates from vacuum energy which creates matter to facilitate the manifestation of life in three ( or four , if we consider space-time also), dimensional material world. Quantum science has established that by constant , continuous and consistent intention ( mind involved )  
    observations can be created to observe , meaning all scientific observations are
    subjective and not a single one is unadulterated objective observation including  the observation of ” space- time” a non- material entity created to localize matter in.

    All these could be derived from the considerations of microbes the ” nano-
    particles “of life- energy.                   

    Sent from

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  8. 8. Torbjörn Larsson, OM 5:41 pm 12/20/2012

    My original comment was never approved (too many links?), so the current one is an orphan. Sadly, I didn’t make a backup.

    Let me see what I can reconstruct:

    - I was critical of the paper, since it predicted but didn’t test survivability in super-cooled water.

    Also, I didn’t see that they checked for spore or cyst formation before or under the growth experiments.

    Cysts are easier to evolve but not so tough (membrane hardened), endospores takes a long time to evolve but tough (special cytoplasm conditions, but needs DNA controlled cell division to form) – endospores evolved in bacteria and eukaryotes, first after archaea split off – and both messes with viability assessment. [See Wikipedia for references on bot, I'm not going to link this time.]

    - If this extended biosphere is viable, it will help prokaryote dispersal during early high impact ratios from dispersing debris disks. This part is what my correction referred to, life can this way more easily survive high impact rate conditions.

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  9. 9. Torbjörn Larsson, OM 5:49 pm 12/20/2012

    @dadster: No, the first time use of controlled experiments with certified good null blankets means this is entirely new stuff.

    As for your last comment, we don’t observe any extraordinary separate “life-energy”, even less have extraordinary evidence needed.

    Same goes for “free will”. (One can make a predictive choice effective “will” theory, though.)

    But this has nothing to do with the extent of the current biosphere and its ramifications.

    @vinodkumarsehgal: It’s “trans-planetary”, not “trans-interplanetary” (transpermia).

    That said, any new extremophile environment makes transpermia more likely, as transport and transplantation survivability increases.

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  10. 10. Torbjörn Larsson, OM 5:51 pm 12/20/2012

    Oh, now my original commentary is back. It appears I have some browser script troubles. My apologies.

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  11. 11. Quinn the Eskimo 9:58 pm 12/22/2012

    So, all of this considered, excluding the rumors of life on Mars, when I dusted my apartment today, I WAS CLEANING ASIA???

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  12. 12. American Muse 10:17 am 12/25/2012

    Can life on this planet migrate away from the “earthosphere” and colonize other celestial objects?

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  13. 13. bucketofsquid 11:43 am 12/27/2012

    @American Muse – The proper term is currently “Terrestrial Biosphere”. Yes we can migrate out from Earth if we have sufficient will and resources to do so. This would be somewhat akin to the Polynesians setting out in large canoes upon the Pacific with nothing on the horizon and no hope of survival if they didn’t hit land before the drinking water ran out. It will take a substantial investment to launch enough building materials and personnel to make the moon or Mars exploitable in a cost effective manner. Until space exploitation pays for itself there will be little motivation beyond pride for such endeavors.

    I hope it happens within my lifetime but I’m not holding my breath.

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