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Rare Earth? Not Enough Data to Know

George Dvorsky takes on the ‘rare earth’ hypothesis in his Sentient Developments blog, calling it a ‘delusion’ and noting all the reasons why life in the galaxy is unlikely to be unusual. The post reminds me why the book that spawned all this was so significant. Rare Earth: Why Complex Life is Uncommon in the Universe (Copernicus, 2000) is Peter Ward and Donald Brownlee’s take on our place in the cosmos, concluding that complex life is rare because an incredibly fortuitous chain of circumstances must arise for it to occur. Indeed, the authors argue that large parts of our galaxy are composed of what they call ‘dead zones.’

The argument is complex and looks at factors ranging from a planet’s place in the galactic habitable zone (itself a controversial subject), its orbit around its own star, its size, its satellites, its magnetosphere, its plate tectonics, and more. I’m surprised to realize, looking through our archives here, that I haven’t managed to do a complete review of Rare Earth in the past five years (although we’ve certainly kicked its ideas around during that time). I’ll remedy that soon, because I think it’s a hugely significant work. Agree with it or not, the authors have laid out a strong case that has inspired spirited rebuttal, and the study of astrobiology has benefited from the insights they’ve brought.

Back to Dvorsky, who notes Charles Lineweaver’s work suggesting that planets began forming in our galaxy long before our own Sun ever ignited, and goes on to look at progress in exoplanetary science, which is uncovering so many new worlds. The point George is making is that there have been vast amounts of time for life to arise, and a huge range of galaxies within which it could evolve. He’s absolutely right, but I’ll part with him on the use of Gliese 581 c to make the case on life’s odds:

…shockingly, the first Earthlike planet was discovered in 2007 orbiting the red star Gliese 581. It’s only 20 light-years away, 1.5 times the diameter of Earth, is suspected to have water and an atmosphere, and its temperature fluctuates between 0 and 40 degrees Celsius.

If we are one in a billion, then, and considering that there are only 0.004 stars per cubic light-year, what are the odds that another Earthlike planet is a mere 20 light-years away?

But the odds are still where they were, Gliese 581 c now being generally considered too close to its star to be habitable. The next planet out, Gl 581 d, is possibly within the extreme outer edge of the habitable zone, and perhaps a better bet for life than what now seems to be a hellishly hot Gl 581 c, but in any case neither of these massive ‘super-Earths’ are truly Earth-like, and the question of whether they support life or not awaits further data. Recent work by Brian Jackson, Richard Greenberg and Rory Barnes suggests tidal heating for Gl 581 c that may be three times greater than what we see on Io, not a promising sign.

We still, in other words, don’t have a good read on how close the nearest habitable planet is, or how rare our Earth may be. Could Ward and Brownlee still be right? Absolutely. At this point we lack the data to know.

Alan Boss has much to say about all this, and George goes on to quote him to good effect. Author of the recent The Crowded Universe: The Search for Living Planets, Boss (Carnegie Institution) sees Earths as ‘incredibly common,’ going on to make this astounding statement: “…every solar-type star probably has a few Earth-like planets, or something very close to it.” Take that, rare Earthers!

I just finished The Crowded Universe the other day and will have more to say about it soon — we looked at its author’s ideas on habitable planets in a previous post. I tend to go along with Boss, as least in so far that I suspect life is quite common elsewhere in the universe, and probably complex life at that. But the question of sentient, technology-building life is quite another matter. It wouldn’t surprise me at all to find many living worlds in our galaxy, but of necessity we await the results of our explorations, one of which was so recently launched. One day Kepler’s successors will doubtless flag the spectroscopic signature of a living world, but barring a SETI breakthrough, the question will remain. Are there other civilizations? Do they too dream of traveling to the stars?

Comments on this entry are closed.

  • yeti101 March 11, 2009, 17:28

    love the rare earth debate, i just hope Peter Ward and Donald Brownlee are wrong!

    kepler is the first test for earth like planets lets hope we find some and clear the first hurdle. Assuming we do it may take scanning the atmospheres of thousands before we find one thats similar to ours.

  • Enzo March 11, 2009, 18:56

    I’ve read “Rare Earth” quite a few years ago , don’t remember everything from it, but I seem to remember that the point they were making is not that earth like planets are rare, but that complex life is. They seemed to think that simple, bacterial life was indeed common, even in places like Europa and Pluto.

    Their point was that Earth didn’t have multi-cellular life until relatively recently (< 1Gyr ago ?). And that, during that time, Earth had been relatively stable with few cosmic disasters etc.

    A consequence of this is that intelligent life is even rarer, something that would help explain the Fermi paradox.

    I have to say that I found it pretty convincing but of course with little data to go on about it could be completely wrong. Of course is unappealing : a universe teaming with complex life and planet to visit with weird ecosystem is much more interesting, but that doesn’t make it any truer.

    And another thing : evolution and natural selection push towards more and more efficient replication, but not necessarily in the direction of multicellular or intelligent development. On Earth it has taken a long time to get to multicellular organisms and bacteria are still doing very very well.
    Similarly, cockroaches have been around only 350 Myrs and still doing very well too, even with an intelligent specie around. And for how long we’ll be around remains to be seen, thanks to our stupid bacterial growth that assumes an endless world.
    In summary, you do not have to be multicellular or intelligent to be successful.

    To, “Rare Earth” doesn’t seem to be so absurd. Their conclusion might be unappealing, but not implausible and more observations are needed.

  • kurt9 March 11, 2009, 19:39

    I just received my copy of “The Crowded Universe”. Until I finish reading it, I remain a “rare earth” proponent for the following reasons:

    1) Plate tectonics and the Giant Impact:

    I believe that plate tectonics is essential for the emergence of complex life and possibly for any life. Without plate tectonics, a planet will undergo the periodic global resurfacing that Venus has done. I believe each of these resurfacing events would wipe out all life on the planet and might even make the planet into a Venus-like hellhole each time they occur. It is also likely that the giant impact that created our moon also created the conditions for plate tectonic to occur. This is because the giant impact stripped away 70% of the Earth’s crust to make the oceanic crust thin enough for subduction to occur. Also, the impact may have removed most of the water as well. Without it, the Earth would have been a waterworld.

    2) The Eukaryote:

    Nick Lane, in “Power, Sex, and Suicide”, makes a very compelling argument that the emergence of the Eukaryote was the result of such a wildly improbable chain of events that it likely has not occurred anywhere else in the galaxy.

    3) The emergence of intelligence:

    The Earth has stable periods ranging from 50 million to 150 million years where life evolves between mass extinctions. We are the product of the most recent stable period, which is 65 million year. The previous one was the one that the dinosaurs lived in, which was about 150 million year long. The fact that no intelligence appeared during this period, having been at least twice as long as our own, is suggestive of the fact that the emergence of tool-making intelligence is rare.

    So, it appears that we are the winners of at least 3 lotteries in a row. it is not only too early to declare the rare earth hypothesis dead, I maintain that it is still quite likely to be the actual state of affairs.

    Kepler is unlikely to answer this question. Kepler will be able to detect the presence of Earth “sized” planets around the various target stars. However, it will not be able to characterize those planets such to determine atmospheric content, let alone detect the presence of plate tectonics. This will have to be done by a follow-on mission.

  • Goldstein Hovercraft March 11, 2009, 19:49

    I agree with Enzo, but moreover, what I really liked about Rare Earth was what it taught me about Earth itself, as it covered fields of science that I don’t usually read about. Even if we somehow discovered today that complex life was very common, Rare Earth would remain an interesting read. In other words, for this book, the journey is more important than the conclusion.

  • Ross March 11, 2009, 21:45

    Another thing to consider, earthlike planets might be common, but how many would be at the same evolutionary stage, and close enough in space so that if they had advanced civilizations on them capable of sending interstellar messages, they would be able to find and communicate with each other?

    A million civilizations could rize and fall on different planets in different parts of the galaxy at different times in the lifespan of a galaxy, and there might never be more than one or two at the same time at a level capable of communicating with each other. It’s not hard to imagine if there was more than one, they would not be close enough to contact each other.

    Fermi’s paradox might not be a paradox, when time is taken into account. One author in a recent article concluded: There won’t be any star trek. Maybe we shouldn’t expect the Vulcan’s to appear on our doorstep any time soon, even if life bearing worlds are common.

  • Chance March 11, 2009, 21:51

    Doesn’t the existence of Europa show that the idea of narrow habitable zones is probably flawed? There may be few Earths, but many, many Europas out there. Admittedly Europa may be sterile or have only simple life, but still…

  • David March 12, 2009, 0:20

    None of the GJ 581 planets are transiting so we
    can’t say that GJ 581c has a diameter 1.5 times that of Earth. Going back to the Bonfils et al. (2007) discovery paper, that size figure quoted applies only if the exoplanet had the same composition of Earth. A planet largely of Iron would be smaller and a water planet would be larger.

  • bigdan201 March 12, 2009, 2:32

    yes, and cockroaches are still doing well in spite of our attempts to kill them, lol.

    simple life is probably common in the cosmos.. it can arise here on earth in almost any environment. “extremophiles” have been found living and flourishing in places like antarctica, the ocean floor, heavily polluted water, chemical waste, and even radioactive waste. i also read that theres some form of moss growing in the remains of chernobyl.

    life can exist in a wide range of environments, so we cant assume that exo-life requires earth-like conditions to survive. other life may live in hotter or colder planets, maybe underground to avoid radiation, or on the surface with a natural resistance to radiation. it might float in gas giants. it might not even be based on carbon, but on another element.

    complex life of course is not as common as simple life, but i dont see its existence as being far fetched. naturally, ETI is another story entirely – we could have simple and complex biospheres on other worlds without there being intelligent life.

    with the number of stars and galaxies though, im sure there are civilizations out there – we already know at least one occured, around a main sequence star, on a terrestrial water planet of the type that can be found elsewhere. finding them of course is another matter.. ETI in other galaxies would be much harder to find than ETI that happened to share our galaxy.

    on a somewhat related note, I had an idea – taking observations of the earth, spectroscopic or otherwise, would help us in finding earthlike planets. has anyone capitalized on that yet?

  • GOU Limiting Factor March 12, 2009, 3:19

    Another oft-overlooked scenario is intelligent non-technological or non-industrial life.

    If we assume all intelligent life is inherently technological (as we do, unavoidably, with signal-search programs like SETI), or that all intelligent technological life will go through an industrial revolution, we’re discarding a potential cornucopia of worlds with intelligent life.

    It offers a corollary to the Fermi Paradox: we only have the one unequivocal example, ourselves, and so our ability to recognize intelligent life is sharply limited.

  • Didac March 12, 2009, 4:04

    Of course, intelligent life is far less abundant than non-intelligent multicellular life and multicellular life is far less abundant than unicellular life. That said, however, we all remember the pre-extrasolar planet discoveries era (a mere 15 years ago). In those times, the idea of “Rare Solar System” was very widespread. People thought that planets were only possible in “one-star” systems with proper metallicity, etc.

  • Steve March 12, 2009, 5:47

    “And another thing : evolution and natural selection push towards more and more efficient replication, but not necessarily in the direction of multicellular or intelligent development.”

    True, so far as we know. But that’s the key, *As far as we know*. I think the fact is until we *find* life on another world, and thus have a base of comparison, we should be carefull when thinking about what evolution and natural selection can’t do.

    I have a hunch – not scientific, I know -that evolution can do a great deal if life just gets a foot hold, producing lifeforms most diverse and wonderful, as someone said! And is quite capable of producing life *as we don’t know it*.

    Time will tell.

  • Ronald March 12, 2009, 7:16

    @Enzo: agreed, and even more so. I am afraid: few people realize how huge (and poorly understood) the first gap is: that from lifeless organic chemistry to the first living cell. Even one cell seems to be the symbiosis of several primordial organisms or ‘pre-organism’ complexities (larger cell, nucleus, mitochondria, maybe even ribosomes).

    As I argued before, we may even find many potentially suitable planets (right temp, primordial atmosphere, water, etc.) without any life.

    Only time and effort will tell. No good theory or model beats observation and discovery.

  • Ronald March 12, 2009, 7:23

    Further to my previous post: and even that situation (rare life), though disappointing at first, need not be hopeless, it would just change the possibilities and responsibilities for humankind: terraforming and seeding planets with adapted forms of our earthly life, i.e. bringing the spark of life to otherwise lifeless worlds. While preserving the rare occasions of inhabited planets with great care and respect, as cosmic reserves.

    Professions of the future, besides of course advanced forms of rocket science, might be planetary engineering and bio-engineering.

  • ljk March 12, 2009, 9:10

    Ronald, your comment about our “responsibility” to seed at least
    the Milky Way galaxy with life brings up the old question about if
    there were at least one other intelligent technological species in
    the galaxy who felt the same way, why don’t we see any evidence
    of their actions?

    For starters, WE could be one of the results of their actions to
    bring life to the galaxy. Or even more likely our small and brief
    efforts are far from what is needed to seriously detect alien life at
    just about any level. Or maybe they did try and their efforts failed.

    In any event, this just further shows why we need to directly
    explore other star systems if we are ever going to answer what
    is probably the most important question ever. Or at least get
    those space telescopes built and going that can supposedly
    image continents on exoplanets.

  • Administrator March 12, 2009, 9:37

    ljk writes:

    Ronald, your comment about our “responsibility” to seed at least the Milky Way galaxy with life brings up the old question about if there were at least one other intelligent technological species in the galaxy who felt the same way, why don’t we see any evidence of their actions?

    Yes, and of course this ties in with Lineweaver’s estimates about Sol-class stars being available for planetary system development a couple of billion years before our own Sun formed. You would think an effort to seed the galaxy would be detectable unless there are reasons why self-reproducing probes can’t achieve the task. On that score, andy’s objections to ‘ancient probes’ in the earlier thread do seem reasonable.

  • Administrator March 12, 2009, 9:44

    Re Ross’ statement:

    Another thing to consider, earthlike planets might be common, but how many would be at the same evolutionary stage, and close enough in space so that if they had advanced civilizations on them capable of sending interstellar messages, they would be able to find and communicate with each other?

    An excellent point, also interesting in light of Lineweaver’s conclusions. And of course it gets to the question of just how long a technological civilization can expect to survive. We have the tools to ensure our own destruction now. If most civilizations do this not long after they produce such tools, the chances of contact between civilization would drop hugely. We would be left with the prospect of exploring ruins around other stars, at best.

  • Ronald March 12, 2009, 11:58

    @bigdan: “simple life is probably common in the cosmos.. it can *arise* here on earth in almost any environment”
    Well, I’d rather say that it can *adapt* to almost any environment, not just a word game, but very essential: life’s arising may be very rare, but once it gets a foothold, it can creep almost anywhere.

    @Ross: good point, it may all be a matter of (very) narrow overlapping temporal windows of opportunity. From that perspective it would even be very strange if intelligence, or at least technological intelligence were common, even taking into consideration Lineweaver’s publication and another relevant one ‘Coming of Age in the Galaxy’. A window of opportunity of, say, 10,000 years is extremely little in comparison with sunlike stars being roughly in their same gigayear of stellar evolution.

    @ljk: excellent point! Also in combination with the previous (by Ross): advanced intelligences may be long gone, but may have left their planetary legacies.

    I think, ljk, that you answer your own, very relevant, question, in this regard:
    “why don’t we see any evidence of their actions?”
    –>
    “Or even more likely our small and brief efforts are far from what is needed to seriously detect alien life at just about any level.”
    “In any event, this just further shows why we need to directly explore other star systems if we are ever going to answer what is probably the most important question ever. Or at least get those space telescopes built and going that can supposedly image continents on exoplanets.”

    We are not even able yet to detect and spectroscopically analyze any earthlike planets (or moons).

    If we ever find a striking abundance of the same, and with strikingly similar characteristics, this might actually be a telltale that a galactic gardener, long gone itself, has left a heritage. A moving thought in a way. Otherwise, that galactic gardener is going to be us, for the first time, equally stirring.

  • Ronald March 12, 2009, 12:01

    Sorry, the second publication, I referred to is: “Coming of Age in the Milky Way” by Timothy Ferris.

  • Athena March 12, 2009, 23:02

    Rare Earth contained a large number of errors and selective evidence for propping up its thesis. A major consultant of its two authors was Guillermo Gonzalez, later unmasked as an unabashed creationist.

    I reviewed Rare Earth for The Seti League in an essay titled E. T., Call Springer-Verlag! This is the nugget of the review:

    “In science, theories cannot be identical to their predictions, nor can their predictions be trivial. In fact, the rare earth theory is neither hypothesis nor prediction, but a description of how life arose on Earth.”

  • Administrator March 13, 2009, 8:02

    Athena, thanks for the link to your review — I want to quote this from it on selective evidence:

    In Rare Earth, the authors present the theories they favor as complete and widely accepted, masking the fact that many are controversial (for example, whether star metallicity is as rare as they describe and whether Cambrian Ediacarans represent additional extinct phyla). Furthermore, I spotted errors in my field of expertise (conflation of transcription and translation, a 20-fold exaggeration of the number of human genes — both pertaining to the crucial concept of complexity) and a howler regarding the rotations of Mars and Venus (which are not locked, as the authors assert in their haste to make Earth unique in the solar system), These missteps make me wonder whether the authors misquoted additional facts instrumental to their hypothesis.

    Good points indeed! Let’s also quote this:

    Given our current almost total lack of knowledge, such books serve as reviews of existing evidence and as mirrors of the philosophical preferences of their authors; as such, they quickly become obsolete.

    Lack of data remains the problem.

  • kurt9 March 13, 2009, 12:27

    I’ve read “Rare Earth” and have just finished “The Crowded Universe” (I read this last one in a single sitting). Athena’s points are correct. There are other parts of “Rare Earth” that have been challenged as well. For example, it appears that Jupiter may have attracted as many comets to hit the Earth as it has protected the Earth. None the less, one key point that “Rare Earth” brings up that remains valid is the issue of plate tectonics and their relevance to the evolution of life. Earth’s got them. Venus and Mars do not. It is possible that Mars may have had them in the distant past, but this remains controversial. Another valid point that “Rare Earth” brings up is the relevancy of having a large moon.

    It is believed that our moon is the result of a massive collision between the original Earth and a Mars-sized object and that this collision was just right to strip off much of the Earth’s crust (and some mantle) such to make the moon, but not enough to completely shatter the original Earth. What “Rare Earth” does not do is link the moon forming giant impact with the creation of the conditions for allowing plate tectonics.

    I still think much of “Rare Earth” is still valid, regardless of whatever religious motivations the authors may have had in writing it.

    “The Crowded Universe” is quite good. I even think Boss is correct, as far as the implications of the information he presented in the book. It is likely that Earth SIZED terrestrial planets are common in the universe. However, Boss says nothing about issues such as plate tectonics, large moons, and the like, not to mention biological issues such as the evolution of the Eukaryote. To his credit, he states that he is not qualified to comment on the biological issues because he is not a biologist and that such discussion is beyond the scope and intent of his book.

    I have found that both “Rare Earth” and “The Crowded Universe” are excellent books. The second is much more empirical in that Boss is unwilling to climb out on a limb except to defend the slightly more controversial “disk instability” theory of planet formation. The evidence seems to support this theory.

    I believe that the issues of plate tectonics and the evolution of the Eukaryote and what not are such that, even if every F, G, K in the galaxy had an Earth-sized world in their Goldilocks’s orbits, that the Earth could possibly be the only planet in the galaxy with complex life.

  • Administrator March 13, 2009, 14:31

    Like you, kurt9, I liked Boss’ candor, especially in being upfront about what he views as his own limitations re the biological issues. I also appreciated the extensive summation of exoplanet discovery highlights. We’ll have more to say about The Crowded Universe in these pages.

  • andy March 13, 2009, 15:59

    I don’t buy the rarity of plate tectonics arguments, since giant impacts would appear to be fairly common occurrences during planet formation. The subset that result in moon-formation might be small, but moon formation is not necessary to blast significant quantities of material off a planet (the reason for Mercury’s proportionally large core?)

    And large moons would not be so necessary for planets around less luminous stars. In between the regime where solar tides are insufficient to stabilise a planet against severe axial wandering and the regime where tidal locking occurs, intermediate-strength solar tides could also function as axial stabilisers, provide tidal pools on shorelines, etc.

    Tectonics is also not necessarily rare: bear in mind Venus is very dry (plus the high temperature/pressure conditions at the base of the atmosphere, which is perhaps better regarded as a supercritical ocean, may well have an effect – I’ve seen a study which suggests that the temperature gradient through the outer layers of Venus is likely too small for significant tectonic activity thanks to the high surface temperatures), Mars is small and getting cold on the inside. Neither is a particularly good analogue for Earth, where the presence of water helps lubricate the subduction process.

    As for Earth being the only planet with complex life, I seriously doubt it. Earth represents one route to doing it, there are likely others. Maybe the only planet with Earthlike complex life?

  • Adam March 13, 2009, 17:05

    What andy said.

    Plus: There’s hints of granite on Venus so it might have been much wetter in the deep past.

    And plate tectonics proper might not have begun until very late in Earth’s evolution – some estimates put the beginning of the current tectonic cycles to the Proterozoic, just a billion years ago. Prior to that the mantle motions and asthenosphere that underly the motion of continents and the birth/death of seafloors were developing via a series of stages. Venus and Mars might represent early stages that have been frozen in place by other processes – mantle dehydration and mantle cooling respectively.

  • ljk March 13, 2009, 17:12

    David Darling also addressed the Rare Earth concept and the
    book of the same title in his 2002 work Life Everywhere, which
    you can read about, including the first two sections, here:

    http://www.daviddarling.info/works/life_everywhere.html

    As I recall, Darling brought up the issue of Guillermo Gonzalez’s
    creationist religious beliefs with Ward, who did not seem to
    realize his bias.

    Gonzalez was later co-author of the seriously biased and just
    plain awful book The Privileged Planet. You just have to read
    the bio of his co-author to see where he and the book stand:

    http://www.privilegedplanet.com/authors.php

    As with any other theory, if creationists want to claim that a
    “higher power” made the Universe, which they promote as
    being especially made for humanity despite having at least
    100 billion galaxies full of stars and loads of planets, they
    need to come up with much more convincing real evidence
    than they have presented so far.

    “Life is so complex it could not possibly have been made by
    chance” isn’t it.

  • Athena March 13, 2009, 22:03

    The trouble that Gonzalez created is actually reflected in some of the comments in this thread: Gonzalez had a decisive input into the theories of Ward and Brownlee not only when they wrote Rare Earth, but also in a later article that all three co-wrote. The article appeared as the cover of Scientific American, in which they further advanced the concept of uniqueness and extended it to the entire universe (Gonzalez, G., Brownlee, D., & Ward, P.D. (2001). Refuges for life in a hostile universe. Scientific American, October issue, 60-67).

    Both the book and the article have since seriously and consistently skewed debate in astrobiology. I can only hope that the Kepler mission will be one more nail in the coffin of this persistent revenant.

    Here is the extremely relevant portion of an interview with David Darling in Salon in June of 2001:

    “I contacted Peter Ward and asked how much Gonzalez influenced him in the writing of the book. He replied, “He’s been a major influence about the importance of some features of the earth that are unique to Earth and that we believe are important in the rise of complex life.” I then said to him, “Did you know that Gonzalez writes extensively as a Christian apologist, defending the view of intelligent design?” And he said, “No, I had no idea of this. Are you sure?” Then he wrote to Gonzalez and asked for an explanation and Gonzalez said he wasn’t making any apologies for the fact that his religious beliefs affect his science and vice versa.”

    [snip]

    And I have no problem with creationist people, but the fact is that it is influencing the public perception of where astrobiologists stand. “Rare Earth” sold over 100,000 copies, which is extraordinary for a science book. My concern is that if the public is persuaded that there isn’t very much of interest out in space other than bugs, then it might eventually filter through and stifle the very means by which the question can be decided.”

  • kurt9 March 14, 2009, 2:17

    Andy,

    Do you have a link to information about plate tectonics being of only 1 billion years old on Earth? I would like to read more about this. Your suggestion that the heavy bombardment early in a planet’s history may be sufficient to strip a crust and make plate tectonics make sense. I know that Mercury is essentially sans crust. Venus may well lack tectonics for the reasons you give. It is currently believed that the lack of tectonics is the reason for the periodic resurfacing the planet undergoes every 300-500 million years.

    I stand by my point with regards to the Eukaryote. I recommend Nick Lane’s “Power, Sex, and Suicide”

  • andy March 14, 2009, 7:13

    You’d have to ask Adam for the reference to the young plate tectonics idea – he was the one who mentioned it.

    As for the evolution of the eukaryote being essential for complex life, consider the many-celled magentotactic prokaryotes. Multicellularity is not limited to the eukaryota.

  • David March 14, 2009, 11:15

    Adam, could you supply a reference to the possibility
    of there being granite on Venus.

    In case anyone doesn’t know, its thought that the formation of granite requires water which is why this is interesting.

  • Athena March 14, 2009, 11:41

    People are often impressed by the complexity of something outside their own field. That’s why they can be blinded by “geniuses” who propose bold, groundbreaking theories that haven’t been thought of by experts — though they neglect to mention that these theories have often been investigated and debunked by the experts.

    The rise of the eukaryotes is one such point for non-biologists (the emergence of vision is another, as is intelligence). Although there is no denying whatsoever that these are extremely complex processes, there is nothing so improbable about them that they would occur only once per universe. Intelligence, in particular, may have been developing in other species, but they didn’t get the time window that we did. Once we became intelligent and then technologically dominant, that was the end of the line for any other potentially sentient terrestrial species. We won a lottery, indeed. Had the dice fallen differently, these words might have been written by velociraptor descendants.

    For the record, the mitochondrial hypothesis was first proposed by Lynn Margulis pretty much in its current form, and was derided for quite a long time before it became obvious that it was correct, confirming the dictum that “scientific theories start as heresies and end as superstitions”.

  • kurt9 March 14, 2009, 13:57

    As for the evolution of the eukaryote being essential for complex life, consider the many-celled magentotactic prokaryotes. Multicellularity is not limited to the eukaryota.

    According to Nick Lane, these were eukaryotes at one point in the past, then retroevolved to prokaryotes and that multicellularity is limited to the eukaryote.

    Plate tectonics may or may not be common. Kepler is not going to find this out for us because it does not have the capability of directly observing these planets.

    However, further exploration of Mars should give us some clue. If Mars did have plate tectonics in the past, then it is likely they are common. If not, the question remains open. What does appear clear is that an Earth-sized planet without them is going to have these periodic global resurfacing events, like Venus, and I cannot help but think that these are bad for life.

  • kurt9 March 14, 2009, 17:29

    It is clear from reading “Rare Earth”, and especially their follow-on book, that its as if Brownlee and Ward want to believe that Earth-like planets are rare. I, on the other hand, would be delighted to be shown that plate tectonics are common to Earth-sized worlds.

    It clear that Gonzales is unapologetic about allowing his religious beliefs to bias his science. However, his sole contribution to astrobiology, the galactic habitable zone, is a reasonable idea. One of the things that Kepler will definitely answer for us will be the correlation between stellar metallicity and the presence of planets, particularly Earth-sized ones. If this correlation is shown to be weak or non-existent, then we can safely discard the idea of a galactic habitable zone.

  • Adam March 15, 2009, 19:45

    Hi All

    Those references to our current plate tectonic regime being “recent” are manifold, usually with a different take on exactly how the late stages of tectonics differ to the early stages. A search on Proterozoic plate tectonics will bring up some.

    As for the Venus granite news here’s Universe Today’s report…

    Venus Possibly Had Continents, Oceans

  • ljk March 15, 2009, 20:21

    While on the one hand you can say there is no solid evidence for
    life of any kind beyond Earth, the “smoking guns” of the possibilities
    for alien organisms keep growing on a daily basis. Even Ward and
    Brownlee say they think there are lots of planets with at least
    simple life forms on them all over the Universe.

    I honestly think a big part of the reason people keep naysaying
    on *intelligent* alien species is a fear of them brought on not only
    by billions of years of competitive species on this planet but the
    deluge of hostile aliens in science fiction, who all consider Earth
    and its inhabitants to be some rare and valuable prize – despite
    the fact that there are 400 billion other star systems to choose
    from. Our planet’s resources can be found in megabulk all over
    the place, and I would be very surprised if another organic species
    was perfectly adaptable to our environment for living upon.

    We are still in this relatively primitive fear stage about the
    unknown. We are also afraid of being dominated or destroyed
    by beings more powerful than us, based on our long and bloody
    history of what groups of humans have done to each other.
    Our leaders certainly do not want to think there is something
    better and stronger than them. Oh they acknowledge the
    existence of certain deities, but they are conveniently remote
    and always on our side and not our enemy’s.

    There is genuine reason for concern about this. But if we
    remain under our beds, we will not develop as a species and
    we may inadvertently end up inviting the very trouble we want
    to avoid because we don’t want to admit or search for ETI.

    If we continue to ignore the wider Cosmos as so many humans
    do on a daily basis and try to keep up the pretense that we are
    the most important creatures in existence, we will not be prepared
    for what really is out there.

  • Ronald March 16, 2009, 10:12

    @ljk: “I honestly think a big part of the reason people keep naysaying
    on *intelligent* alien species is a fear of them brought on not only
    by billions of years of competitive species on this planet but the
    deluge of hostile aliens in science fiction”

    And not to forget all sorts of religious prejudices, often making people quite geocentric and anthropocentric (“we have to be the only intelligence/only living planet, otherwise we wouldn’t be so special anymore”, “God has made everything especially for us”, etc.).

    Now I have to admit that I am quite G-star biassed ánd carbon-chauvinistic myself.

  • Ronald March 16, 2009, 10:16

    Further to my previous post: but then again, I tend to think that the optimum for ‘habitable stars’ is not our G2, but probably hovers around G5 or G6.

    I sincerely hope this compensates a bit for my shocking confession ;-)

  • Administrator March 16, 2009, 10:28

    ljk wrote:

    I honestly think a big part of the reason people keep naysaying on *intelligent* alien species is a fear of them brought on not only by billions of years of competitive species on this planet but the deluge of hostile aliens in science fiction, who all consider Earth and its inhabitants to be some rare and valuable prize…

    Larry, I’ve often speculated that there are few other intelligent races in the galaxy, and this doesn’t describe my thinking at all. I can’t speak for anyone else, of course, but I think what’s important isn’t the motivations behind peoples’ views as much as the data that will eventually show them to be either right or wrong. Like I said in the original post, we simply need data.

    And hey, there’s plenty of science fiction that doesn’t treat aliens as hostile or malignant.

  • ljk March 16, 2009, 11:59

    Paul, of course I was generalizing but I also think your way
    of thinking on the subject is, unfortunately, atypical when it
    comes to the subject of ETI. By this I mean someone who
    thinks there are few intelligent aliens in the galaxy based on
    current scientific evidence and a heightened knowledge of
    the concept.

    Ask the average person on the street what they think about
    ETI and I am willing to bet that if they don’t find the concept
    ridiculous thanks to the UFO fringe and the immature portrayals
    found on television series and SF films, they will otherwise
    worry about being conquered, eaten, or vaporized by the
    same said aliens.

    We also have those who treat aliens as saviors and gods or
    demons but not beings from our level of reality. Then there
    are the religious fundamentalists I have talked to who “know”
    that nobody else exists in this Universe except on Earth
    because Jesus Christ only came to save the humanity once
    and God would not have him bouncing around the galaxy in
    various forms “saving” other species.

    Ironically, though, you can find Western thinkers in previous
    centuries who not only believed that God would never make a
    planet and then leave it barren, but that God did indeed send
    His Only Begotten Son (or Sons) on endless missions throughout
    the Universe to save all of his lesser creations who had not
    gotten the Message the first time.

    It makes me wonder if some ETI haven’t bothered to contact us
    because their own beliefs either disregard the idea of life on other
    worlds or they are forbidden to find and communicate with aliens,
    or perhaps both. That was the general situation in Western culture
    not too long ago.

    Paul, you are right about some science fiction aliens not being the
    standard villians and monsters, but they are not common, either.
    Since the medium is designed to entertain and usually at the lowest
    common denominator, most fictional aliens are not nice. And this
    does have an affect on the human psyche regarding the subject.

    Hollywood is also in the habit of making money as the bottom line,
    so naturally if Star Trek’s plots consisted of the Enterprise crew
    exploring new planets and finding alien microbes and interesting
    geological formations each week, the series would have died out
    ages ago, assuming it ever even made it to the air in the first place.

    Of course no one will argue that we need more real data on the
    subject, which is why I support SETI and interstellar flight. And
    we sure have come a long way in the last decade or so concerning
    exoplanets, without even having to leave home!

    • Administrator March 16, 2009, 13:12

      Since the medium is designed to entertain and usually at the lowest common denominator, most fictional aliens are not nice. And this does have an affect on the human psyche regarding the subject.

      Larry, you’re going to energize some of the science fiction writers who frequent these pages with that comment about the ‘lowest common denominator’! I find aliens of all kinds in science fiction, and bear in mind that the genre is hardly limited to television and movies.

      When I do think of SF movies, though, I think not only of ‘Independence Day’ and ‘Alien’ but also the original ‘Day the Earth Stood Still,’ ‘ET,’ and ‘Close Encounters.’

  • ljk March 16, 2009, 14:28

    Paul, the medium I was referring to was mainly television and film,
    not the SF novels. There are some nice exceptions, of course, but
    the sad majority is made up of light entertainment and outright junk.

    I have noted there is a new SF trend for more “realistic” worlds,
    with the reimaged Battlestar Galactica leading the way. This will
    of course bring about more mainstream acceptance, but part of
    this so-called realism trend means there are no aliens in BSG,
    unless you count the Cylons.

    The series does, however, bring up the issue of what might happen
    if and when we create a true artificial intelligence. My personal view
    is that a true AI (aka Artilect) might go off and seek more interesting
    pastures rather than try to conquer or destroy us (that alien cliche
    again), but that would not make for compelling television and we
    are left once more with the long influence of Artilects in AI being
    threats to humanity and the subsequent effect it has on the mindset
    of the general populace.

    Boy, when you think about it, our species is paranoid about almost
    everything that is different from it, or what it cannot understand.
    Another reason I think the first real encounter between an ETI and
    a resident or descendant from Earth won’t be by an organic being.

    The novels are much better on the whole, but how many have
    been made into successful cinema or TV series? And even the
    good ones more often than not portray aliens as variations on
    humanity both in terms of looks and behavior. That is fine if
    your agenda is to comment on some aspect of humanity and
    want to do it through the safety net of fictional aliens, but it is
    not terribly common to see a true exploration of an alien mind,
    culture, and biology. I do know they exist, though! :^)

    And about Close Encounters: If those aliens were so benevolent,
    why did they kidnap humans for decades before returning them
    to Earth? These people have not aged a day, which is nice for
    them, but how many of them will have any family or friends left?
    And how will those humans who set up this close encounter ever
    explain these folks sudden reappearance? Or will they be taken
    away and never see mainstream society again?

    And other than knowing that aliens exist, what other knowledge did
    we gain by the dramatic meeting at Devil’s Tower and when do these
    authority types ever plan on sharing it with us? I don’t think
    Spielberg ever addressed this. And why do aliens keep buzzing and
    kidnapping us thirty-plus years after the encounter?

    And how is E.T. able to breathe our air and deal with our gravity
    so easily? And why didn’t they come right back to get him after
    leaving him behind in the first place? A few government types
    with guns should not scare advanced aliens in a starship with an
    FTL drive that makes rainbows.

    • Administrator March 16, 2009, 15:05

      Larry, what a dark interpretation of ‘Close Encounters’! ;-)

  • ljk March 16, 2009, 16:13

    Well, you brought it up. :^)

    I can get even darker, those these are really just in-depth
    observations on a film that wasn’t really all that deep to
    begin with, to say nothing of being rather stereotypical
    regarding aliens:

    How “nice” are these aliens if they deliberately terrify a single
    mother and her young son in their own home and then abduct
    the kid right out the cat door?!

    And the “message” that the ETI implanted in the minds of
    Richard Dreyfuss’ character that compelled him to seek out
    the close encounter site cost him his family, though you get
    the feeling he is now much happier (and still young) aboard
    the Mother Ship, which is good for him but what about his
    wife and kids? And why did Terri Garr always play the wife
    of a husband who gets involved with otherworldly beings
    and never quite gets what’s going on?

    All those other people we saw who tried to get to Devil’s Tower –
    did they trash their jobs and the lives of their families and friends
    to get there too, only to fail in the process thereby gaining what?

    And was the aliens’ homing message meant just for certain
    humans or did they just beam it out across the world to see
    who they could get, like a fishing trawler spreading a huge net
    to capture as many aquatic life forms as possible?

    And what about the skin burns that the two main characters
    received after being exposed to the alien ship for their first times?
    Are these radiation burns from their propulsion drives? Why were
    the aliens so careless if their objective was to study humans in their
    native habitats?

    And if you are going to study a less advanced species to see their
    normal reactions, why do it with giant glowing ships that not only
    burn their subjects and disrupt their lives but also knock out power
    to entire regions and spawn hundreds of UFO reports?

    And what about the police officers in that patrol car who went
    flying over an embankment while chasing a bunch of UFOs
    early in the film? Were they okay? Maybe the aliens did not
    realize what would happen if they went flying off the road while
    being pursued by less advanced vehicles that can’t fly – but then
    how did they know to lift up the tolls gates? And note they did
    NOT pay a toll!

    This is a quote from the Goofs section of the IMDB entry on CEot3K:

    Errors in geography: The latitude/longitude received by the scientists (104 degrees 44 minutes 30 seconds West 40 degrees 36 minutes 10 seconds North) isn’t very close to Devil’s Tower at all. The coordinates are very close to Stage Colorado, east of Ft. Collins, Colorado, almost 300 miles away from the monument.

    If you want a “secret” meeting, why do it in a US National Park and
    have the human authorities come up with some fake story that makes
    the national news and causes the evacuation of thousands of people!

    And if the aliens have been studying us for ages, why didn’t they
    speak in English or some other human language, rather than the
    flahing light synthesizer and hand signals? I mean, they knew
    American Sign Language!

    Spielberg may have wanted some family-friendly film with sugar-
    coated aliens who smile and run around the tarmack with pretty
    lit-up spaceships, but upon closer inspection, I see a bunch of
    aliens who either do not realize or do not care about terrifying
    their study subjects and when they do “communicate” with them,
    it’s over in no time, I am not sure what we got out of the deal
    and I am sure even those tidbits were squirrled away and made
    Top Secret by the Authorities.

    Shall I go on?

    • Administrator March 16, 2009, 16:27

      Better stop now — I’d hate for you to take up your whole day on this :-)

      I rather enjoyed the film myself, though I’ve never been much of a Richard Dreyfuss fan…

  • ljk March 16, 2009, 17:11

    This is fun and doesn’t take up as much time as you think. :^)

    My commentary on Close Encounters started out as a sideline
    to my earlier main points, but the more I thought about it, the
    more I realized what a good example this 1978 film is in terms
    of giving the general public conflicting and often just plain wrong
    information about alien intelligences.

    While I am sure the crew of CEot3K meant to show benevolent
    aliens who only wanted to be our friends in some kind of gesture
    of cosmic harmony, a closer look shows beings who, being more
    advanced and rather different (though still humanoid in shape),
    are not entirely careful when it comes to dealing with a less
    sophisticated species. They also seem to have a somewhat
    iffy sense of the Prime Directive, if at all.

    This is a prime example of what the general public, who gets
    a lot of their “education” from Hollywood films about the world
    and beyond, is being fed regarding ETI. It is not necessarily
    deliberate on the part of the filmmakers, but that is what makes
    it all the more potentially damaging, being wrapped in the cloak
    of entertainment.

    They won’t be thinking more deeply about the concept of alien
    life, and if they do, it will be messed up with UFO stories and
    the conflicting messages of benevolence and terror.

    This is why things like SETI and interstellar spaceships are still
    regarded as less than germaine topics by large segments of the
    general public, though of course the fact that we have yet to
    really establish ourselves in space beyond Earth plays no small
    role in this response.

    I am not foolish enough to think that Hollywood and its cinematic
    bretheren are ever going to stop putting out frothy little bits of
    entertainment on the subject of alien life, but we just need to
    recognize where the public is really getting their thoughts about
    aliens from and what the science community needs to do to “fix”
    these notions. Especially if we ever want to see SETI and missions
    to Alpha Centauri really get off the ground.

  • kurt9 March 16, 2009, 23:00

    Adam,

    Thanks for the link on Venus’s plate tectonics. Also, Mars may have had them in the past as well.

    http://www.esa.int/SPECIALS/Mars_Express/SEMF399OY2F_0.html

    http://www.pnas.org/content/102/42/14970

    It appears that plate tectonics may, indeed, be common to Earth-sized planets.

    I stand by my point about the Eukaryote.

  • Ron S March 17, 2009, 0:03

    I very much doubt that Hollywood is out to either mislead or intellectualize about ET, or any subject for that matter. Their aim is money via mass market entertainment. Sensory overload, be it violence, FX, sex or whatever, seems to work so they continue with that. Sci-fi is fertile ground for FX in particular.

    Most human stories, whether novel, film, theater, are similarly structured on core themes such as conflict and quest on a canvas painted with archetypal elements like mythos, survival and sex.

    ET has to be brought into line with these themes and elements if it is to generate mass market interest (revenue). It has less to do with exploring ET and more to do with bringing in an element of novelty (or current fashion) into a pre-existing formula.

    I suspect that the majority who go to see much of this crud know full well it is entertainment, not a serious exploration of what might be. However if kept on a steady diet of this stuff it may seep into an individual’s subconscious and inform their opinions. Maybe.

  • Adam March 17, 2009, 5:27

    Hi All

    The aliens in “Star Wars”, “Star Trek” and “Babylon 5” were pretty diverse and multifaceted for what coverage they received. I think the general public has gotten used to the idea of friendly aliens at least since Spock & the Vulcans came along. That they all looked human and spoke English is a side issue.

    One thought is that the discussion is moot until we meet ETIs.

  • Ronald March 17, 2009, 5:46

    @ljk: an interesting possibility that you raise in one of your posts, that might explain Fermi’s paradox: cultural and mental complacency, possibly even religiously inspired (maybe even taboo), that would keep an intelligence from exploring the universe.

  • ljk March 17, 2009, 9:52

    Ron S. said:

    “I very much doubt that Hollywood is out to either mislead or intellectualize about ET, or any subject for that matter. Their aim is money via mass market entertainment. Sensory overload, be it violence, FX, sex or whatever, seems to work so they continue with that. Sci-fi is fertile ground for FX in particular.”

    Of course I don’t think there is some kind of deliberate “conspiracy”
    regarding Hollywood’s depiction of aliens. Their bottom line is money,
    money, and more money by whatever means it takes. They figured
    out a long time ago that the majority want light entertainment (aka
    junk food for their brains), so that is what they get. Of course they
    make a few “intellectual” films on the side to look good at Oscar time,
    but the real moneymakers are the fluff.

    More from Ron S.:

    “I suspect that the majority who go to see much of this crud know full well it is entertainment, not a serious exploration of what might be. However if kept on a steady diet of this stuff it may seep into an individual’s subconscious and inform their opinions. Maybe.”

    Exactly. They may know on the surface it is fiction, but eventually
    it sticks in their brains and this is how they think aliens and the
    Universe in general look and work. I am not being facetious when
    I say that a lot of people get their so-called knowledge about the
    world from films and television. School ended for most adults a
    long time ago, but they keep watching TV and films, so this is
    what the know and remember.

    Ronald said:

    “@ljk: an interesting possibility that you raise in one of your posts, that might explain Fermi’s paradox: cultural and mental complacency, possibly even religiously inspired (maybe even taboo), that would keep an intelligence from exploring the universe.”

    Next to the vast distances and billions of star systems that make
    up the Milky Way galaxy (to say nothing of all the other 100
    billion galaxies in the known Universe), this may be one of the
    most critical reasons why we have not found ETI, or they us.

    The idea of extraterrestrial life was not even considered by our
    species until the ancient Greeks. Then the concept was sporadically
    considered for the next two thousand years, with certain authorities
    in the West (thanks in no small part to Plato and Aristotle) denying
    the possibility and punishing those who said otherwise, Giordano
    Bruno being perhaps the best known example.

    Certainly almost no one seriously considered trying to contact
    or visit them (or they us) until just a few centuries ago. And even
    though many think there is life elsewhere today, the ridicule factor
    is still often in place thanks to the UFO fringe and the subpar SF
    stories already cited.

    If other organic beings in the Cosmos are anything like us, and
    it is certainly possible that most life which developed on a terrestrial
    type planet may have evolved in the similar fashion to our own,
    then they too may be taking a long time to accept the ideas of
    stars being other suns which may have planets with life upon them.

    Who knows, maybe we are actually quicker about accepting the
    concept of alien life than other species. It is ironic, though, that
    so many people readily accept the concept of supernatural beings
    everywhere affecting every aspect of our daily lives, but the
    thought of “mortal” beings developing and living on worlds like
    we are is still met with skepticism and ridicule, all because they
    haven’t bothered to drop in and say Hi yet.

  • ljk March 17, 2009, 11:09

    I should also get with the times: Video games are another area
    of influence regarding our perceptions of alien life.

    With the possible exception of Spore, how many other electronic
    games are out there where the aliens are not marauding invaders
    and horrible monsters? And all the spaceships are desperately
    trying to blow each other up.

  • Ronald March 17, 2009, 15:27

    ljk: “It is ironic, though, that
    so many people readily accept the concept of supernatural beings
    everywhere affecting every aspect of our daily lives, but the
    thought of “mortal” beings developing and living on worlds like
    we are is still met with skepticism and ridicule”.

    Yes, this keeps amazing me as well ! people will often believe just what they wish to believe.

  • andy March 17, 2009, 15:48

    According to Nick Lane, these were eukaryotes at one point in the past, then retroevolved to prokaryotes and that multicellularity is limited to the eukaryote.

    Who is Nick Lane? Never heard of him before, and therefore have no idea whether this is a serious claim or not. Reference for where Nick Lane asserts that these organisms are “de-evolved” from eukaryotes?

  • Ron S March 17, 2009, 17:10

    “ljk: “It is ironic, though, that
    so many people readily accept the concept of supernatural beings
    everywhere affecting every aspect of our daily lives, but the
    thought of “mortal” beings developing and living on worlds like
    we are is still met with skepticism and ridicule”.

    Yes, this keeps amazing me as well ! people will often believe just what they wish to believe.”

    I don’t find it surprising. It’s a quite common thread through many religions (and their new age counterparts) that man (tribe, priesthood, prophet, or whatever) has a privileged relationship with one or more divinities. A distinct intelligent species upsets that paradigm, resulting in diverse attempts to rationalize or reject.

    The ridicule comes about because we often laugh at that which makes us most uncomfortable. It’s a psychological aid to ward off unpleasant thoughts, much like garlic is used to ward off vampires. Since the garlic works at that task (I’ve never been accosted by a vampire when I’ve had a clove of garlic handy), laughter can be employed to ward off ET. It, too, seems to work.

    When you stop laughing, and take ET seriously, that’s when you start to believe in the extra-terrestrial origin of UFOs and Area 51 conspiracy theories.