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ESO: Habitable Red Dwarf Planets Abundant

Red dwarfs are all over the news thanks to an announcement by the European Southern Observatory. Results from a new HARPS study show that tens of billions of planets not much larger than Earth are to be expected in the habitable zones around this class of star. The finding reinforces the growing interest in M-class stars and becomes especially interesting when you realize that faint red stars like this make up as much as 80 percent of the stars in the Milky Way. That leaves plenty of room for astrobiology, depending on factors we need to discuss below.

Do we suddenly have a close destination for a potential interstellar probe? Well, Barnard’s Star has always been in the running for an early mission because of its relative proximity to us at 5.94 light years. But we still have no word on planets there (despite a much publicized but soon discredited set of observations from a 1969 paper). Proxima Centauri is available at 4.2 light years, but we have yet to learn whether it has planets. And as far as anything closer, a source on the WISE team passes along the information that no new red dwarfs have been discovered, as of yet, within 10 light years, though of course the WISE results are still under heavy analysis.

Image: This artist’s impression shows a sunset seen from the super-Earth Gliese 667 Cc. The brightest star in the sky is the red dwarf Gliese 667 C, which is part of a triple star system. The other two more distant stars, Gliese 667 A and B appear in the sky also to the right. Astronomers have estimated that there are tens of billions of such rocky worlds orbiting faint red dwarf stars in the Milky Way alone. Credit: ESO/L. Calçada.

But back to the ESO announcement, which focuses on results obtained with the HARPS spectrograph at La Silla. Let me quote Xavier Bonfils (Institut de Planétologie et d’Astrophysique de Grenoble) directly on this:

“Our new observations with HARPS mean that about 40% of all red dwarf stars have a super-Earth orbiting in the habitable zone where liquid water can exist on the surface of the planet. Because red dwarfs are so common — there are about 160 billion of them in the Milky Way — this leads us to the astonishing result that there are tens of billions of these planets in our galaxy alone.”

What the work comes down to is a survey of 102 M-class stars studied over a period of six years, in which nine super-Earths with masses up to ten times that of Earth were found. 460 hours of observing time went into the mix, with 1965 radial velocity measurements made between 2003 and 2009. Interestingly, more massive planets like Jupiter and Saturn turn out to be rare around such stars, with fewer than 12 percent of them expected in M-dwarf systems. From all this, the team thinks that there should be about 100 super-Earth planets in the habitable zones of stars within about 30 light years of the Sun.

We can point to interesting worlds like Gliese 667Cc — discovered in the HARPS survey — as a promising preview of what is out there. This is a planet within a triple star system that is about four times the mass of the Earth and orbits close to the center of the habitable zone. But even assuming an abundance of super-Earths in conditions allowing liquid water on the surface, we still have the old M-class problems to contend with. A habitable world around such a small star needs to orbit close to it, leading to the potential for tidal lock and creating climate conditions that may not favor life. We also know that red dwarfs are frequently flare stars, creating unique evolutionary pressures on any life that does manage to emerge.

Xavier Delfosse (IPAG, Grenoble), another member of the team working the HARPS data, is lead author on one of two papers examining the results that have recently become available. The outlook on tidal locking is troubling but perhaps not a show-stopper for astrobiology, at least not if our own Solar System is any indication. Although a habitable M-dwarf planet is likely to be captured into a spin-orbit resonance, it will not necessarily be forced into synchronous rotation. From the paper (I’ve omitted internal references for brevity — the paper citations are below):

The final equilibrium rotation of a tidally influenced planet depends on both its orbital eccentricity and the density of its atmosphere… Mercury, for instance, has been captured into the 3:2, rather than 1:1, spin-orbit resonance…, and Venus has altogether escaped capture into a resonance because thermal atmospheric tides counteract its interior tides… Whatever the final spin-orbit ratio, the tidal forces will influence the night and day succession, and therefore the climate. As discussed above however, energy redistribution by an atmosphere at least as dense as that of the Earth is efficient… and will prevent glaciation and atmospheric collapse on the night side.

And what about stellar flare activity? M-dwarfs are more active than G-class stars like the Sun, with the result that a planet in the habitable zone of a young M-dwarf takes a huge hit from X-ray and ultraviolet radiation, a period of irradiation 10 times longer than the approximately 100 million years that the Solar System dealt with similar activity on our star. How planetary atmospheres evolve under such conditions, and whether they can actually be stripped away by coronal mass ejections, are issues we haven’t as yet resolved. Digging into the Delfosse paper I find several points worth noting on the matter:

  • We don’t have a good read on just how frequent coronal mass ejections from M-dwarfs are, and how intense they tend to be. Right now these questions need more investigation, though the authors believe the frequency may be less than some earlier studies have indicated.
  • A strong magnetosphere can help to shield a planet that would otherwise be imperiled.
  • The atmospheric chemistry and composition may be key, and there is one study that shows that around active M-dwarfs with an atmosphere consisting mostly of CO2, the atmosphere remains stable despite nearby flare and CME activity.

The paper summarizes the issue this way:

These differences imply that a planet in the habitable zone of an M dwarf is unlikely to be a twin of the Earth. Habitability however is not restricted to Earth twins, and Barnes et al. (2010) conclude that “no known phenomenon completely precludes the habitability of terrestrial planets orbiting cool stars.” A massive telluric planet, like Gl667Cc (M2.sin i = 4.25 M⊕), most likely has a massive planetary core, and as a consequence a stronger dynamo and a more active volcanism. Both factors help protect against atmospheric escape, and super-Earths may perhaps be better candidates for habitability around M dwarfs than true Earth-mass planets.

So there we are: Tens of billions of rocky planets in the habitable zones of red dwarfs, and perhaps 100 relatively near to the Sun, according to the estimates of these researchers. What we need to do now is increase the red dwarf planet inventory with future instruments made to order — state of the art near-infrared spectrographs that, in the authors’ estimate, should be able to identify between 50 and 100 planets in the habitable zones of M-dwarfs. That should be enough, even with a 2-3% transit probability, to find at least one transiting habitable world.

The Delfosse et al. paper is “The HARPS search for southern extra-solar planets XXXV. Super-Earths around the M-dwarf neighbors Gl433 and Gl667C,” submitted to Astronomy & Astrophysics (abstract). The Bonfils paper is Bonfils et al., “The HARPS search for southern extra-solar planets XXXI. The M-dwarf sample,” submitted to Astronomy & Astrophysics (full text). The ESO news release is also available.


Comments on this entry are closed.

  • Greg March 29, 2012, 10:09

    This reminds me of “The Draco Tavern” by Larry Niven, the chirpsithra say they colonized the galaxy but they only live around red dwarf stars.

  • Tulse March 29, 2012, 10:10

    I presume that CMEs and flares don’t have much of an impact on the non-sunward side of a planet, in which case tidal locking might actually be an advantage. As long as a planet has a dense enough atmosphere to redistribute solar energy, this actually be the ideal arrangement for biology on these worlds.

  • Tony P March 29, 2012, 11:22

    Life on the dark side of a tidally locked, but thermally stable, planet orbiting a red dwarf would be a dark world indeed.

  • A.B. Samma March 29, 2012, 14:07

    This may be good news but a recent paper offers tidal induced dessication of earth size planets as a confounding factor against habitable planets especially those that orbit stars with a mass <0.3 solar mass.
    The conclusion is that even if the earth sized planet is at the habitable spot, its close orbit around the star may cause it to end up dry like Venus due to tidal stress.

  • philw1776 March 29, 2012, 14:47

    Folks don’t seem mindful that any such late K or M primary star planets with other than 1:1 spin orbit resonance would have huge tides sweeping any lakes and oceans across the planet’s surface scouring it flat over the eons.

  • Joy March 29, 2012, 15:44

    Ok, this a vast extrapolation from scant data, but plausible enough. What else is there to say? Could any of these red dwarf planets have goldfish shoals?

    Red Dwarf theme song + lyrics
    (extended version, the familiar part starts at 2:35)

  • Alex Tolley March 29, 2012, 15:58

    @ philw1776 But that wouldn’t preclude life adapting to such conditions. As far as humans are concerned, they could live on platforms that floated on the oceans’ sunward side, or in the atmosphere.

    We can speculate all we like, but what we need is some hard data. The numbers of HZ planets hopefully will make good targets for spectrographic observations in time, with the possibility of detecting bio signatures.

  • Rob Henry March 29, 2012, 16:09

    philwi1776, don’t you think it rather cool that intelligent terrestrial life would arise on the world you described near its poles. Strong ocean tides would make their seas much more productive than ours. Our deep oceans are deserts because of nutrient limitations. Our oceans average just 100,000 W per sqKm of dark reaction capture, but in you new setup it could be at least an order of magnitude higher, and have a much larger surface area. You have just created a world that could contain a biosphere that is dozens of times more powerful than Earth’s. Well done!

  • coolstar March 29, 2012, 16:28

    The Barnes et. al paper referenced by A.B. Samma above is a good one and raises lots of important issues. Even on a planet with 1:1 spin-orbit coupling it should be noted that the rotation period will be long enough that a magnetic dynamo may be quite weak, and thus not strong enough to prevent atmospheric erosion. It may also be that such a planet will lack plate tectonics, which raises a host of other issues. And let’s not forget that super-earths are NOT earth analogs in mass and radii, and most of the ones discovered by the HARPS team so far are likely to much more like Neptune, than like the earth. Thus, I think it’s WAY too early to think of late K and M dwarfs as being great places to look for life.

  • andy March 29, 2012, 17:20

    @A.B.Samma: that is certainly something to bear in mind, but it does not necessarily preclude such stars from hosting habitable planets. If the orbital eccentricities of the planetary system were not strongly excited then the heating would be less.

    @philw1776: Now I’m curious. Do you know of any modelling of just how high we’d expect the tides to be on such planets? At what point would we really expect the lakes and oceans to utterly overflow the continents in the way you describe?

  • Randy Kelley March 29, 2012, 17:24

    I find it unlikely that any star of spectral class M will have a habitable planet.
    The super-earths found by HARPS in the habitable zone of M class stars are most likely:
    (a) To be tidally locked and therefore without a magnetic field
    (b) To be blasted by flares
    (c) To lose any primordial oceans because of the solar wind bombarding a planet without a protective magnetic field (like Mars did)
    (d) To develop a run-away greenhouse because of volcanoes producing greenhouses gases that constantly buildup in the atmosphere without being absorbed in an ocean (like Venus did)

  • Ole Burde March 29, 2012, 17:48

    Lets say we have an earthsized planet orbiting just outside the habitable zone of a relatively big red dwarf . The same forces working to acheive tidal lock will also tend to warm up the planet , as in the case of jupiters moons , so it might be warm enough anyhow .
    What would happen if this planet had a really big moon with an orbital period not too many times bigger than the planets own period ? My intuition try to tell mee that some sort of orbital resonance could be possible , where the planets rotation and the mooons period would be “tuned in” to a stable relationship at least for a very long period , and thereby preventing tidal lock of the planet . The energy that otherwise gradually would cause the tidal lock , would in this case mostly become heat .
    Our own solar system keeps surprising whenever new information becomes avaiable , so if someboddy can dream it up , its probably out there somewhere !

  • philw1776 March 29, 2012, 20:26

    @ andy Dole’s “Habitable Planets for Man” has formulae for tidal effects. Without access and w/o having done the calcs recently I would estimate tides in the hundreds of meters minimum, maybe Km in some cases.

  • spaceman March 29, 2012, 21:11

    Encouraging news in light of the news presented earlier this month based on John Rehling’s analysis of the latest round of Kepler data– an analysis implying that HZ earth sized planets are relatively rare around solar type stars. These more upbeat HARPS statistics could mean, M dwarf habitibility constraints withstanding, that there are relatively close abodes for Life.

    Although these statistics are encouraging, I suspect that they may be on the verge of being challenged. The previously announced HARPS results– the ones implying that roughly half of FGK stars have SEN planets with orbital periods of 100 days or less– will in fact be directly challenged tomorrow by two astronomers from the University of Exeter in the UK. This will take place at the 2012 Exoclimes conference.

    If you go to the website of Exoclimes 2012 look for a talk to be given by Alexander Pettitt and F. Pont. You can read the abstract, but the gist of it is that they analyzed the same HARPS GTO 2003-2009 data set as the Geneva team only using a different analysis technique and found a much lower low mass planet frequency. They assert that this lower frequency is in much better agreement with other large scale planet searches. I checked astro-ph/ and found no paper by these researchers backing up their assertions though I suspect one is in prep. By ‘other large scale planet searches’ I am almost certain they are referring to Kepler and the UC NASA eta-earth survey. The eta-earth survey found a SEN planet freq. of 15-20 percent within 50 day orbits, as did Kepler. Greg Laughlin performed an analysis to see whether Kepler and HARPS could be reconciled. I am not an astrophysicist, but the Laughlin paper reconciled the two data sets by suggesting that Kepler is missing small radius very dense planets that HARPS was detecting.

    To tie all of this back in with today’s post, it seems likely that if Pettitt and Pont are challenging the Geneva team’s analysis for planet frequency around solar type stars, then they will challenge the M dwarf results based on similar grounds.

    The ultimate tie breaker here may be Kepler. All analyses thus far have compared HARPS with the Kepler results from Feb. 2011. Several pieces of evidence strongly suggest that the latest batch of 1000 plus candidates will bring Kepler and HARPS into much better agreement regarding the issue of small planet frequencies. Look no further than John Rehling’s data table showing the frequencies of planets of various radii within different orbital separation bins. A visual inspection and simple addition shows that the frequency of planets from app. 2-6 earth radius (the probable radii range of most of the HARPS planets) easily agrees with the Geneva team’s results.

    By the way, if you do a google search of ‘Exeter planet fever’ you will see the same HARPS debunker, F. Pont, using very odd language– referring to recent exoplanet research as being a type of ‘planet fever’ and how he was going to introduce a ‘vaccine’ against the ‘contagion.’ Such bold provocative language, used at a 2009 AAS meeting, is unprofessional, pejorative, and grandiose. My prediction is that each Kepler data release going forward will agree more and more with the Swiss HARPS analysis and F. Pont only being remembered for eccentricity (and no, I am not referring to orbital eccentricity).

  • Rob Henry March 29, 2012, 21:58

    Ole Burde, tidal forces may work admirably to warm a bodies core, but not really at warming its surface. Volcanisms would just give small regions with HZ temperatures, and these shouldn’t be particularly stable.

    An Earth analogue with 1000x our rate of tidal energy release might be interesting but it would only have 2% of our heat levels from its tides. A world 10,000 times as active yet still just outside the traditional HZ should be rare (I think) since even M7’s should be marginal, leaving only M8 and M9 stars as possible hosts. Anyhow, such a world would be many times more active than Io.

  • Rob Henry March 29, 2012, 22:42

    Sorry Ole, I should have also commented on your idea of adding a massive moon. Here the solution must lie between the Roche and Hill sphere of the planet. Normally that is not much of a requirement, but I think it might be here. Note that if tidal force from the star ever reduces the planets spin faster than the moon is approaching, the moon will be orbiting faster than the planet rotates. That should result in a dramatic acceleration in the rate that the moon spirals into its planet at the best of times, eg Deimos should fall 2,000km and disappear within the next 10 million years. I am sure that someone has already worked out how long such a setup could last, and would love to hear if anyone knows.

  • andy March 30, 2012, 3:37

    @spaceman: The Exoclimes 2012 conference has already happened back in January. I see no reference to a talk by Pont and Pettitt on the website. Are you sure it is Exoclimes 2012 you are talking about?

  • spaceman March 30, 2012, 10:28

    @Andy: Thank you for bringing this to my attention. You are correct. I had the two conferences mixed up in my mind. The one in which Pettitt and Pont presented their work today is the Exoplanets meeting of the Royal Astronomical Society, as this year’s Exoclimes indeed already took place. I found it by going to the ‘meetings’ list on the Extrasolar Planets Encyclopedia. The Royal Astronomical Society Exoplanets conference is listed at the top of the page.

  • ljk March 30, 2012, 14:40

    spaceman said on March 29, 2012 at 21:11:

    “By the way, if you do a google search of ‘Exeter planet fever’ you will see the same HARPS debunker, F. Pont, using very odd language– referring to recent exoplanet research as being a type of ‘planet fever’ and how he was going to introduce a ‘vaccine’ against the ‘contagion.’ Such bold provocative language, used at a 2009 AAS meeting, is unprofessional, pejorative, and grandiose. My prediction is that each Kepler data release going forward will agree more and more with the Swiss HARPS analysis and F. Pont only being remembered for eccentricity (and no, I am not referring to orbital eccentricity).”

    I wonder what Pont’s religious background is? He might be just a really conservative by-the-book scientist, but when I see someone getting real touchy about anything having to do with extraterrestrial life – especially when actual evidence is involved – there usually seems to be more to the story than just a really thorough scientist.

  • henk March 30, 2012, 16:37

    I wonder what Pont’s religious background is? He might be just a really conservative by-the-book scientist, but when I see someone getting real touchy about anything having to do with extraterrestrial life – especially when actual evidence is involved – there usually seems to be more to the story than just a really thorough scientist.

    just because someone is skeptical does not mean he must be religious. We just see what kind of evidence he show to back up his claim. If someone will claim that 90% of all stars will have a earthsize world with life will you than reject the same ?

  • Mike March 30, 2012, 17:28

    “Gentlemen, skepticism is our business.” At least if you are a scientist. Let the the data show.

  • andy March 30, 2012, 17:44

    The danger is that this is all based on small-number statistics and also on one instrument which may have various systematic effects. Getting another instrument with similar precision to HARPS on the sky will be a very welcome development! The current situation leaves conclusions very vulnerable to things like assumed priors on the distributions and such like, and it definitely seems to me that the large size of the error bars is not being communicated nearly as well as the best-fit value.

  • philw1776 March 30, 2012, 20:40

    andy is spot on. Without well described error bars these small # conclusions are suspect. I plead guilty s an impatient redhead wanting to know the #s NOW. The good news is that data continues to flow. These are great times.

  • Ole Burde March 31, 2012, 8:24

    Rob Henry
    “tidal forces may work admirably to warm a bodies core, but not really at warming its surface. Volcanisms would just give small regions with HZ temperatures, and these shouldn’t be particularly stable. ”
    Wouldnt the extra heat eventually be ballanced by an equal amount of heat being tranferred to the surface , by whatever heattransfer-mecanisms could be accelerated by the lack of symetry in the general situation ? It could ofcourse take several billions of years , but then red dwarfs have very long lives , and could as an average be much older than earth .
    Eventually such a planet could be a varm enough to moove the habitabble zone slightly outwards , and this could perhabs be enough to decrease the tidal forces to something that can be neutralized by the lowering of the moons orbit , if this was big enough or a “doubble planet” . In our own earth-mooon system ,it works the other way round , energy is beeing transferred from the earths rotaition to the moons orbit , but in the case of a spinn-orbit resonance this could be expected to behave as as a ballanced system RESISTING any change in its status . If it started far enough out , the stablity period could be long enough to be relevant from a human perspektive . The chance of finding such a planet could be bigger than an earthtype . The hardest question is if such a ” Self Organized ” or tuned -in proces would actually occur . The anwer may lie in understanding our own systems present “adult” stablity as oposed to its violent youth .

  • spaceman March 31, 2012, 15:16

    @Henk: If you read the abstract for Pont’s 2009 AAS DPS talk you will see that the nature of it is more like a rant against the exoplanet community rather than conservative carefully worded skepticism. Frankly, it borders on bizarre and I have seen nothing comparable to it in all of my years of reading abstracts for astrophysics conferences. It begs the question: Is this how a truly conservative “by the book” scientist would want to address/present himself or herself? For example, I am currently reading Allegra Goodman’s “Intuition” which is a novel about the trials and tribulations of research scientists. In one of the chapters, a laboratory leader is thinking about how to word their grant proposal to the U.S. NIH. In doing so he also had to take into consideration the tendencies of his close colleague– a colleague who happens to be much more conservative in her approach to doing science and writing about science then he. So, he contemplated using more subdued language in the grant proposal so as not to cause a divide with his more conservative colleague. Again, you all can decide for yourselves, but I would hardly describe the bizarre rant of F. Pont as being something that a truly conservative scientist would compose, as there is an air of grandiosity, certainty, a sort of I am going to set things straight for all of those in the community who are caught in the proverbial fog. Here is the exact abstract:

    “Super-earth Detection and “Planet Fever”

    Pont, Frederic; Aigrain, S.; Zucker, S.
    American Astronomical Society, DPS meeting #41, #31.07

    “Radial-velocity spectrographs and space transit searches have become sensitive enough to detect planets only a few times more massive than the Earth – the telluric planets or “super-Earths.” We are getting one step nearer to knowing how common are Earth analogs. There is a catch however: many of the super-Earth detections are very close to the detection thresholds, and intrinsic stellar variations are an important source of false positive with both the radial velocity and transit technique. In preparation for the coming harvest of new detections, it seems worth attempting to develop some vaccine against the most extreme strands of “planet fever,” the contagious disease of seeing extra-solar planet in any signal.”

    I believe some of F. Pont’s education took place at University of Geneva. This is the same place where the Swiss team of HARPS researchers come from (e.g. Michel Mayor). Perhaps these two had a falling out of some sort (e.g. I want to one up my higher up), since that AAS DPS abstract has an “I have an axe to grind” feel to it.

    As for the results coming out of the Swiss team’s analysis, so far they have been peer-reviewed. They have been accepted for publication in a scientific journal. I am not an astrophysicist, but I am pretty sure that the initial HARPS Kepler super-earth frequency discrepancy may have been alleviated by the latest round of Kepler data. Look no further than John Rehling’s analysis, albeit the first planet occurrence analysis based on Kepler’s latest, and you will see (using his table of planet radii and frequency for different orbital period bins) that counting even half the planets in the 1.8 to 2.8 Earth radius bin and all of the planets in the planets in the 2.8 to 4.0 Earth radius bin you will easily reach, if not pass, the 0.50 mark for planet frequency within 100 days. Also, go to Rehling’s Centauri Dreams from earlier this month and you will see that the Kepler data already imply several planets per star with most of those planet existing in short orbital periods. This strongly suggests that the Geneva team’s analysis of the 2003-2009 HARPS data set is correct and Kepler is, if you will, catching up with Mayor et al implied planet frequencies the longer it observes stars in the constellation Cygnus.

  • Tarmen April 1, 2012, 9:23

    This is an exiting time of dicovery. We are at the beginning again. Just like the ancient Greeks trying to imagine and visualize and visit the far away places across the sea. They imagined men with horse bodies and such.Maps depicting large blank ‘wastelands’. Soon enough, they learned about many strange things for certain. Not centaurs maybe, but monkeys, Huns and Himalayas. The so-called ‘wastelands’ were not waste at all!! I am sure that we will find similer about our ‘wastelands’….

  • Nick April 1, 2012, 14:35

    Wow, that’s quite a reaction to a short abstract. One piece of evidence that Pont, Aigrain, and Zucker are on to something about “planet fever” is the heated reaction in response.

    What these authors are observing is one branch of a larger religious phenomenon: strong beliefs, despite only very speculative “evidence” in favor of them, and good arguments against them, in the commonality of life (and for many of ETI as well) in our galaxy. Here are some symptoms of this contagion:

    * The bizarre phenomenon of “scientists” proclaiming methane as a signal of life, when it is one of the most common abiotic molecules in the universe.

    * The similarly weird phenomenon of interpreting a spike in one of the most common spectral lines of the most common element (hydrogen) as a “WOW” signal of ETI.

    * Rushing to interpret little ovoids found in Martian meteorites as fossils of bacteria.

    * The odd obsession with a technique best suited for communicating through planetary atmospheres (radio) when looking for ETI.

    You don’t have to believe in other mythological entities to not believe that a large number of planets in our galaxy harbor life. But apparently there are many, including in the scientific community, who feel compelled to believe in some kind of wonderful thing beyond what has actually been observed. Thus Percival Lowell’s canals on Mars, and thus today’s “planet fever.” Indeed a whole “scientific field” has hopefully called themselves “astrobiology”. We might as well have a community of anthropologists set themselves up as “dwarfologists” and go making field trips to mines to look for the telltale signs. How about let’s study real things?

    So yes, we should worry about “the contagious disease of seeing extra-solar planet in any signal”, especially when dubious statistical estimates of the number of “habitable” planets are at issue. Fortunately, actual observations of actual planets will sort this issue out soon enough. The same can’t be said for astrobiology.

  • Rob Henry April 1, 2012, 18:50

    Nick, may I be so bold as to suggest that the evidence that you see as indicative of an outbreak of planetary fever actually better fits the proposition that the consensus is being forced into unscientific stances by the general adoption of a paradigm approach to science.

    It is true that methane seems to be one of the most common abiotic molecules. It is also true that it is rapidly destroyed through photolysis, and attempts to synthesise its production by proposed abiotic mechanisms fail (all good catalysts get choked by a coating of oil). Rather than admit impasse, what you are seeing is the arbitrary adoption of one clear stance.

    In the case of ALH84001 this is even more obvious. There were may indications that this rock once held life, and so it was interpreted as such. This belief was retained when further examination showed these indications to be less convincing than they first appeared. But in this case we have a counterpoint of the Viking life tests. In the second case, though all tests passed predetermined criteria as indicating signs of life, the low levels of organic material lead to a consensus that they had failed to detect life. Such a belief has been clung to even though we now know how misleading those tests were on life containing samples from unusual terrestrial soils.

    To me the real mystery is why a known human failing (the want of creating coherent stories where they don’t exist) has been institutionalised into the methodology of modern scientists.

  • Daniel April 1, 2012, 21:03

    By the way

    For those who don’t expect Many Earth-size exomoons Let’s see how many of this 100 exomoons light signal isn’t a exomoon:

    “The Hunt for Exomoons with Kepler project has identified around 100 potential light curves that could reveal moons orbiting alien worlds already found by the Kepler Space Telescope.”


  • spaceman April 2, 2012, 3:07

    @Nick: Pont is on to something, really? If anything, I think the “planet fever” take on the state of current exoplanet science does not cohere with the facts. First of all, it has taken decades of painstaking analyses, new telescopes, improved spectrographs, faster computers, etc. to get to the state where we are today of being able to finally detect planets in large enough numbers so as to get an accurate picture of the galactic planetary census. Second, lots of effort is put into making sure that signals are really planetary; for example, the Swiss team, using HARPS, looked for and failed to find evidence for the planet Gliese 581g. The progress being made is certainly grounds for the existing optimism. Just because a field that for many years was relatively stagnant is now making enormous progress does not make those who are responsible for accelerating that progress victims of a ‘contagion.’ This is why Pont et al comment is distasteful, unprofessional, and grandiose.

    I wouldn’t be so quick to call the estimates for the number of small planets in the HZs of red dwarfs ‘dubious.’ The approximately 40% figure reported by the Geneva team– although it is based on a relatively small sample size– happens to agree quite well with estimates coming from Kepler’s Feb. 2011 data set in which the science team reports that small planets with short orbital periods are actually quite common (occurrence rate 30-40% so far) around MK type stars. Furthermore, it is probably even more in agreement with the latest Kepler data since more planets have been found around the same number of observed stars. No where did the Swiss team say anything about the planets having life just that small planets around small stars in short period orbits are probably quite common. Fortunately, science marches on and the error bars will shrink and the estimates will be refined, as HARPS is on-going and there are other planned very precise RV programs specifically dedicated to the M dwarf population.

    I fundamentally disagree with your views on astrobiology and ‘how about studying something that is real?” Astrobiology is a broad interdisciplinary field and those involved study a variety of phenomena in hopes of gaining a better understanding how common or uncommon life may be in the Universe. It is a new scientific field fueled by imagination and creativity mixed with some excitement over what we are learning and may yet come to learn through additional probing. What may not be “real” today may be reality tomorrow and that is part of what makes not just astrobiology but all cutting-edge science so valuable. Finding other life in the Universe would easily qualify as one of the greatest breakthroughs of all time, and astrobiologists are getting us to expand our imaginations in terms of what might constitute life, where it might be found, what form it might take, and so on. Astrobiology uses the various areas including biology, planetary science, chemistry, physics, and in some cases engineering to help us get our bearings in our cosmic habitat. Who might we be sharing that habitat with is a fascinating and worthwhile question. As Sagan said: “All species become either space faring or extinct.” How important then it is for us to start investigating in earnest our context within the larger Universe given that our survival will ultimately depend on a detailed knowledge of this vast realm.

  • kzb April 2, 2012, 7:38

    Only the other week we had the article on here about the frequency of Earth like planets being as low as 0.7%. That was extrapolating the Kepler data. Now we have extrapolated HARPS data giving 41% (confidence range 28 to 95%) of M-stars hosting a 1-10 Earth-mass planet in the liquid water range. Presumably, when extended to sub-Earth mass, but still habitable, planets, this frequency can only go up.

    I think we can only wait for the positive detections, rather than statistical extrapolations.

  • henk April 2, 2012, 12:20


    that is true. If they are correct, than we are going to find 100 of planets inside the habitable zone zone in a few years. I only think there sample of planets is a little small.

    about that 0.7% that was about sunlike stars and not about red dwarfs. It is possible that red dwarfs have far more planets in the habitable zone than sunlike stars. we will see in the next kepler data.

    every year they come with new models how many stars has a planet with life.
    i want to see those planets now, not more statistics

  • andy April 3, 2012, 2:57

    Evolution of magnetic protection in potentially habitable terrestrial planets

    Essentially argues that for Earth-mass planets, M, K and even late-G stars would be unsuitable for habitable conditions, for dM stars only the most massive super-Earths would retain habitable conditions.

    Not entirely sure I am convinced yet, would prefer actual data on this…

  • andy April 3, 2012, 2:58

    (Oops, link failed in previous, here it is again)

  • Ronald April 3, 2012, 11:15

    kzb: the 0.7% is a very lower limit, the median estimate is somewhere around 3-4% (and the upper limit is even considerably higher). So, rare is a very relative concept, as is even admitted by Rehling himself in follow-up comments.

  • Ronald April 3, 2012, 11:42

    andy: but, according to the same article, prospects are considerably better for larger planets, even below real super-earth mass: a 3*Me planet could retain its atmosphere and remain habitable as close as 0.1 AU around a M or late K dwarf.
    It would be nice to have a graph of ‘minimum planet mass for long-term habitability’ (defined, say, as atleast 3 gy) versus ‘minimum HZ distance (in AU)’, the latter corresponding with stellar mass, spectral type and luminosity. If the former is on the y-axis and the latter on the x-axis, it would show a line (curve) going from upper left to lower right (closer-in HZ requires larger planets). However, to the right the curve might go up again, because of more aggressive radiation from large mass/hot stars (F). It will also be suddenly cut off to the right, because very large mass/hot stars (A, early F) evolve so quickly that they will not allow a HZ to exist long enough.

  • ljk April 4, 2012, 10:17

    When it comes to alien life, optimists are considered unrealistic and their insistence on there being other beings in the Universe is discounted as believing in fairies and bordering on a religious zeal. Heck, it’s probably even seen as old fashioned in these hard, cynical times. But act skeptical and you are not only considered probably right but you get to join the “cool kids” in their club house. Human are still so damn tribal, but they let their shiny toys dissuade them from this fact.

    As usual Percival Lowell is dragged out as an example of what happens when you have an enthusiastic person conducting their own interpretation of what looks like evidence for ETI. But one century later we know a lot more, including the fact that there are LOTS of exoplanets out there of all varieties: It is only a matter of time before we find the kinds that *can* support numerous forms of life. Earth may be a single data point, but our world is proof that it has happened at least once.

    And for the record, Lowell did so much more for getting the public interested in astronomy and alien life than all those stuffy, insular scientists who opposed him. To this day scientists like Sagan and Tyson who dare to give the masses more than the scraps from their findings are looked down upon in various ways. Thankfully the Information Age is changing this old attitude.

    It remains so painfully clear that the human race still thinks it is the most important thing in the Universe. Especially because no other intelligences have made any obvious attempts to contact us or otherwise let us know they are out there. As if such beings might not have anything better to do. We have a long way to go before we can make any determinations about extraterrestrial life.

    I happen to see lots of real, scientific evidence that it exists, but I am willing to wait for the actual results to come in. But I do not and will not accept that we are alone in the Universe just because ETI aren’t trying to get our attention. And yes, I think a lot of this negative attitude and desire not to have any celestial neighbors comes from those in power wanting to remain the biggest kids on the block and religious attitudes that God made the Universe just for us. You all know it is too damn early to say there is no one else around. Fifty years of sporadic SETI, a few probes sent across the Sol system, and nothing to even the nearest star is hardly the final say on the matter.

  • anoooo April 4, 2012, 23:44

    I have been wondering about tidal-lock study…

    Can a big moon counter tidal-lock from the main star? Like, if mercury/venus have moon, can they actually spinning instead having orbital resonance? If it can, what is the lowest limit of the moon’s mass and it’s distance to the planet (the formula of barycentric coordinate) to counter the tidal lock?

  • Nick April 5, 2012, 2:16

    spaceman: “[Astrobiology] is a new scientific field fueled by imagination and creativity.”

    As are other genres of fiction. It takes plenty of imagination and creativity to “study” something that has never actually been observed.

    ljk, you put forward the tenets of the SETI faith very articulately. Alas, the main problem with SETI is not that ETI “aren’t trying to get our attention.” Why should they? Are we trying to get the attention of ants? Nevertheless, if any ant is anywhere nearly as close to being aware of their environment as we our of ours, they would certainly be aware of the existence of humans — our artifacts are all over their environment in a blatantly obvious manner.

    The problem with the SETI faith is that wherever ETI exist, across millions of observed galaxies, they must be blatantly violating a principle that all life on earth follows, namely the Malthusian imperative. The Malthusian imperative means that lifeless volcanic islands soon get colonized by life, that a forest (given sufficient water and other nutrients to sustain it) soon absorbs nearly all the available sunlight, and so on, regardless of the fact that these activities make the results highly detectable from afar. Couple the Malthusian imperative with technology millions of years more advanced than our own, and all the surfaces of a galaxy containing any ETI whatsoever should soon look blatantly artificial, just all the surfaces of a forest give off blatant signs of highly evolved life. Straightforward spectrography with our current telescopes (or even many of those of the last century) would readily detect said surfaces. The Malthusian imperative thus produces results that are very attention-getting all on their own, without any need for an intent to gain attention. (Although of course in large economies and political systems we also have plenty of people trying to get each others’ attention, in forms such as advertising and propaganda).

    What you can’t explain is why every one of the billions of ETI you must be positing in readily observable galaxies (if there are even a thousand in our own, and thus any in radio range) so blatantly violate the Malthusian imperative that we can’t even observe the artifacts of societies hundreds of millions to billions of years more technologically advanced than ours. The main response I’ve heard from the SETI acolytes when faced with these facts is that all ETI everywhere mysteriously behave just like elves and fairies — without exception they grossly violate the Malthusian imperative by applying practically all their advances to blending into and hiding within a pristine natural environment and practically none to expanding in it and altering it. Or like dwarves they hide deep in mines and never venture up to alter the surface. In other words, the SETI faith, besides conforming to certain prejudices of the very recent, unprecedentedly rich leisure class, is, more importantly, conveniently unfalsifiable, just like other mythologies. We can’t detect ETI for the same reasons we can’t detect elves and dwarves, because they are all without exception good at hiding from us. So the critics of SETI are not the ones inventing these creatures — it is the advocates of SETI who are, to try to explain away the fact that their beliefs blatantly contradict our actual observations of the cosmos and life.

  • Eniac April 5, 2012, 20:55


    And for the record, Lowell did so much more for getting the public interested in astronomy and alien life than all those stuffy, insular scientists who opposed him.

    So all who opposed Lowell were stuffy and insular? Don’t they even get credit for having been right?

    I happen to see lots of real, scientific evidence that it exists, but I am willing to wait for the actual results to come in.

    Normally, in science, the real scientific evidence comes from actual results. I am a little baffled how you can see lots of the former before there is any of the latter.

  • ljk April 6, 2012, 15:34

    Eniac said on April 5, 2012 at 20:55:


    And for the record, Lowell did so much more for getting the public interested in astronomy and alien life than all those stuffy, insular scientists who opposed him.

    “So all who opposed Lowell were stuffy and insular? Don’t they even get credit for having been right?”

    Yes, many of them were. I do not have the luxury of time to list all their names and check on their personalities, so sweeping generalizations will just have to do for now. And since we all know they were right about the Red Planet since 1965, I see little point in giving them even more credit.

    I am just glad that Lowell never lived to see just how dead and lacking in artificial canals Mars really is. Even the new John Carter film probably would not have been enough to comfort the man.

    Eniac then said (after me):

    I happen to see lots of real, scientific evidence that it exists, but I am willing to wait for the actual results to come in.

    “Normally, in science, the real scientific evidence comes from actual results. I am a little baffled how you can see lots of the former before there is any of the latter.”

    I tend to blend the word “evidence” in with the word “clues”. Such as in lots of organic molecules in interstellar space and lots of alien planets to me are clues that the odds are pretty good we are not alone in the Milky Way galaxy and beyond. When I want to say something actually exists in reality ande can be quantified by science, I tend to use the word “proof”. My apologies for any confusion.

    I really do not know for absolute certain if alien life exists in reality in our Universe yet, but I guarantee you I will let everyone know the moment I do have proof of it. But I am pretty sure most worlds that aren’t totally nasty do have at least the equivalent of microbes and stromatolites. And I don’t think more intelligent creatures, including ones like us, are all that hard to come by either, but that’s another story.

  • ljk April 6, 2012, 15:41

    You got me, Nick – SETI is indeed a religion and we acolytes all worship the Supreme Deities circling the galactic core around NGC 5907. Whew, I feel so much better now that the truth is out there!

  • ljk April 10, 2012, 21:01

    National Geographic Channel produced a program called Extraterrestrial, which looked at hypothetical life around different kinds of alien worlds.

    One of them depicted a world orbiting a red dwarf. The entire program is here:


  • ljk September 5, 2012, 12:44

    Further evidence that there are many habitable planets for humans to colonize

    George Dvorsky

    An international team of scientists working at European HARPS have announced the discovery of a large rocky planet residing within the stellar habitable zone of the red dwarf star Gliese 163. That increases the number of known potentially habitable planets to six — the majority of which have been discovered in the past year.

    To better understand the significance of the discovery, we contacted Abel Méndez, an Associate Professor of Physics and Astrobiology in the Planetary Habitability Laboratory at the University of Puerto Rico at Arecibo. Méndez told us that the detection of Earth-like worlds is pacing up — and that there’s likely a lot more to come.

    “There are more observatories dedicated to these types of searches, “he told io9, “and many of them now have the required sensitivity to find these potentially habitable planets.”

    Full article here:


  • ljk December 18, 2012, 11:29


    The Physics arXiv Blog

    December 18, 2012

    Three Habitable Zone Planets Discovered Around One Red Dwarf

    A red dwarf that is itself part of a triple star system, hosts three planets in its habitable zone, says astronomer

    Gliese 667 is a triple star system about 22 light years from Earth in the constellation of Scorpius. Two of these stars–Gliese 667 A and B–are Sun-like and orbit each other relatively closely.

    The third is much more interesting. Gliese 667C a red dwarf that is about a third of the mass of our Sun and only about 1 per cent as bright. It orbits the other two stars at a much greater distance: some 200 astronomical units or about 30 billion kilometres.

    Red dwarfs are particularly interesting for astronomers because their small mass makes it much easier to spot orbiting planets. What’s more, their low luminosity means that these stars’ habitable zones are much closer than for brighter stars.

    Since current planet spotting techniques favour closer planets, astronomers know they are much more likely to find planets in the habitable zone around red dwarfs. In fact, today’s news is a good example.

    Today, Philip Gregory at the University of British Columbia in Canada says that Gliese 667Chas three planets sitting squarely in the middle of its habitable zone.

    Gregory is a pioneer of new statistical techniques for evaluating the data from planet-hunting instruments. “The excitement generated by … many … exoplanetary discoveries has spurred a significant effort to improve the statistical tools for analyzing data in this field,” he says.

    So he’s used a new technique to re-examine data on Gliese 667C taken by the High Accuracy Radial velocity Planet Searcher, HARPS, attached the European Southern Observatory’s 3.6 metre telescope in Chile.

    He says this analysis indicates that the most likely number of planets around Gliese 667C is 6 with orbital periods of 7 days, 28 days, 31 days, 39 days, 53 days and 91 days. Only two of these were already known.

    However, the most interesting news is that the 28, 31 and 39 day-planets are all smack bang in the middle of the habitable zone, he says.

    These planets are all larger than Earth but the 39 day period planet (planet e) is only just over twice Earth’s mass. That makes it “the lowest mass planet in the habitable zone detected to date,” says Gregory.

    That’s exciting news which will make Gliese 667C the target of significant interest in the near future from astrobiologists wanting to know more about these potentially Earth-like places. And with three to examine around a single star, they will be spoilt for choice.

    Ref: http://arxiv.org/abs/1212.4058: Evidence for Multiple Planets in the Habitable Zone of Gliese 667C: A Bayesian Re-analysis of the HARPS data