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A Kepler-438b Caveat (and a Digression)

Before we go interstellar, a digression with reference to yesterday’s post, which looked at how we manipulate image data to draw out the maximum amount of information. I had mentioned the image widely regarded as the first photograph, Joseph Nicéphore Niépce’s ‘View from the Window at Le Gras.’ Centauri Dreams regular William Alschuler pointed out that this image is in fact a classic example of what I’m talking about. For without serious manipulation, it’s impossible to make out what you’re seeing. Have a look at the original and compare it to the image in yesterday’s post, which has been processed to reveal the underlying scene.


Image: New official image of the first photograph in 2003, minus any manual retouching. Joseph Nicéphore Niépce’s View from the Window at Le Gras. c. 1826. Gernsheim Collection Harry Ransom Center / University of Texas at Austin. Photo by J. Paul Getty Museum.

And here again is the processed image, a much richer experience.


The University of Texas offers this explanation of how the image was made:

“Niépce thought to capture this image using a light-sensitive material so that the light itself would “etch” the picture for him. In 1826, through a process of trial and error, he finally came upon the combination of bitumen of Judea (a form of asphalt) spread over a pewter plate. When he let this petroleum-based substance sit in a camera obscura for eight hours without interruption, the light gradually hardened the bitumen where it hit, thus creating a rudimentary photo. He “developed” this picture by washing away the unhardened bitumen with lavender water, revealing an image of the rooftops and trees visible from his studio window. Niépce had successfully made the world’s first photograph.”

As with many astronomical photographs, what the unassisted human eye would see is often the least interesting aspect of the story. While we always want to know what a person looking out a window would see, we learn a great deal more by subjecting images to a variety of filters.

Meanwhile, in the Rest of the Galaxy…

Habitable zone planets are a primary attraction of the exoplanet hunt, but so often a tight analysis shows that what we know of a world isn’t enough to confirm its habitable status. Kepler-438b is a case in point, a world that is likely rocky orbiting a red dwarf some 470 light years away in the constellation Lyra. The planet orbits the primary every 35.2 days, but writing in these pages last January, Andrew LePage estimated there was only a one in four chance that Kepler-438b is in the habitable zone, declaring it more likely to be a cooler version of Venus.

Now we have more evidence that a planet some in the media have called ‘Earth-like’ is in fact a wasteland, its chances of life devastated by hard radiation from the host star. Kepler-438 produces huge flares every few hundred days, each of them approximately ten times more powerful than anything we’ve ever recorded on the Sun. These ‘superflares’ are laden with energies of 1033 erg, although energies of 1036 erg have been observed.

But the flares are part of a larger problem for Kepler-438b. They are associated with coronal mass ejections (CMEs), a phenomenon likely to have stripped away the planet’s atmosphere entirely. In work to be published in Monthly Notices of the Royal Astronomical Society, David Armstrong (University of Warwick, UK) and colleagues analyze conditions around the red dwarf. Armstrong explains in a University of Warwick news release:

“If the planet, Kepler-438b, has a magnetic field like the Earth, it may be shielded from some of the effects. However, if it does not, or the flares are strong enough, it could have lost its atmosphere, be irradiated by extra dangerous radiation and be a much harsher place for life to exist.”


Image: The planet Kepler-438b is shown here in front of its violent parent star. It is regularly irradiated by huge flares of radiation, which could render the planet uninhabitable. Here the planet’s atmosphere is shown being stripped away. Credit: Mark A Garlick / University of Warwick.

The relationship of flares and CMEs is complicated, as are the effects of a magnetic field. From the paper:

It is possible that CMEs occur on other stars that produce very energetic flares, which could have serious consequences for any close-in exoplanets without a magnetic field to deflect the influx of energetic charged particles. Since the habitable zone for M dwarfs is relatively close in to the star, any exoplanets could be expected to be partially or completely tidally locked. This would limit the intrinsic magnetic moments of the planet, meaning that any magnetosphere would likely be small. Khodachenko et al. (2007) found that for an M dwarf, the stellar wind combined with CMEs could push the magnetosphere of an Earth-like exoplanet in the habitable zone within its atmosphere, resulting in erosion of the atmosphere. Following on from this, Lammer et al. (2007) concluded that habitable exoplanets orbiting active M dwarfs would need to be larger and more massive than Earth, so that the planet could generate a stronger magnetic field and the increased gravitational pull would help prevent atmospheric loss.

A coronal mass ejection occurs when huge amounts of plasma are blown outward from the star, and the extensive flare activity on Kepler-438 makes CMEs that much more likely. With the atmosphere greatly compromised or stripped away entirely, the flares can do their work, bathing the surface in ultraviolet and X-ray radiation and a sleet of hard particles. For a time, Kepler-438b looked so intriguing from an astrobiological standpoint, especially with its small radius 1.1 the size of Earth’s, but it takes an optimistic assessment of the habitable zone indeed to include it in the first place, and it now appears that the chances for life here are remote.

The paper is Armstrong et al., “The Host Stars of Keplers Habitable Exoplanets: Superflares, Rotation and Activity,” accepted at MNRAS and available as a preprint.


Comments on this entry are closed.

  • Hop David November 18, 2015, 10:42

    I am still wondering how many gas giant icey moons have liquid water beneath their crusts. Not only can these be outside the Goldilocks zone, they’d also be rad hard. Europa’s icey crust would be more than enough radiation protection even within Jupiter’s monster Van Allen belts.

    I’m not sure what sort of energy flux tidal stretching/squeezing can provide though. I imagine it’s much smaller than the bounty we enjoy from sunlight. If there are “smoker colonies” on Europa or Enceladus, they are likely much less active than earth’s ecosystems.

  • Ronald November 18, 2015, 10:56

    The sobering conclusions in this post with regard to M dwarfs and the habitability of their planets, particularly with regard to tidal locking and flares/CME, confirm my solar chauvinism when it comes to planetary habitability.
    Besides a stellar HZ and a Galactic HZ, there seems to be a (stellar) spectral HZ as well: too large stars (‘early’ spectral types) are too short-lived and emit too much aggressive radiation, too small stars (‘late’ spectral types) will have tidally locked planets in their HZ plus flares/CME.
    The Goldilocks spectral range is from ?? (G7/8/9?) to ?? (K0/1/2?).

    BTW, I wonder what the age of Kepler-438 is. Until what age is flaring and excessive CME a problem in M dwarfs?

  • Harry R Ray November 18, 2015, 10:58

    Here’s my take on Kepler 438b. The new data may actually INCREASE the chances of life there, but with a HUGE CAVAET: ONLY if we discover living organisms in the recurring slope linea on Mars! Here’s my logic: If the combination of no magnetic field AND superflares turning a young Venus INTO an OLD Mars in a few gigayears, there would be a point where very earth-like conditiond would have prevailed. If sufficient water were REDILIVERED to the surface during that time period, there should STILL BE underwater aquifers there NOW! If, at the ANTISTELLAR POINT(i.e. ASSUMING total tidal locking) the water is EXTREMELY BRINEY, it could survive the bitter cold in a liquid form. If life was REGENERATED in the “Earth-Like conditions” period, extremeophiles like Dieniochis Radiodurans could exist underground, but very close to the surface. NOW: On a much lighter(I HOPE) note, page 8 of this paper states the age of Kepler 62 as “14.6 plus or minus 0.6 Billion years, meaning that the ERROR BOX MINIMA is 14 billion years, or 300 million years OLDER than our universe! If this is true, then there is a K5 civilization there that was able to MOVE THE ENTIRE SYSTEM from an OLDER parrallel universe to ours! Obviously NOT(I HOPE true. but where is the proof-reading here!

  • Harry R Ray November 18, 2015, 11:35

    This finding most likely dashes ANY hopes for NASA studying the atmosphere of Gliese 1132b with JWST, because there is a VERY HIGH PROBABILITY of strong CME interaction THERE TOO, meaning there is no atmosphere there to study!

  • Harry R Ray November 18, 2015, 11:42

    Ronald: Kepler 438 is 7.1(plus or minus 0.4) billion years old(see page 8 of the PDF).

  • RobFlores November 18, 2015, 11:50

    Considerer these Red Dwarves, CME/Flares

    If the CME/flare rate is extremely active, on the order several
    hits on the average world per month,
    Could a living organism in the icy regions of such a solar system
    evolve to use the CME/flare matter/energy or the resulting surface chemistry to power themselves and/or grow.
    Since the Icy regions of such a system would start closer to where venus would be, it would be still be quite energetic when it hit an Icy planet/moon.

  • Robert Feyerharm November 18, 2015, 12:32

    Even with a planet orbiting closely to an M dwarf star, if we assume coronal mass ejections are localized phenomena and erupt in a random direction from the star’s surface, what are the odds the direction of the CME would happen to coincide with the planet?

  • TLDR November 18, 2015, 13:27

    Correct me if I am wrong, but The HZ or habitable zone is a distance at which the amount of a star’s radiation is similar to that of our Sun.

    Now factoring in things like a star’s stability, etc., is about the slipperiest slope in this galaxy. Where do you stop? An exoplanet’s magnetic field? The number of continents? Comet and asteroid strikes in the past million years?

  • Keith Cooper November 18, 2015, 13:55

    @Harry R Ray
    We don’t know for sure that 438b doesn’t have an atmosphere – if it has a substantial magnetic field it could still protect itself somewhat, though it would have to be a stronger field than Earth’s. But we don’t know if planetary systems around other red dwarfs are the same until we look. Plus, just like the MAVEN spacecraft has observed the solar wind stripping away Mars’ atmosphere and water, telling us something about the history of Mars, scientists will want to learn more about that process, and planets around red dwarfs might be the ideal laboratory.

    Kepler-438 might also be an outlier. Red dwarfs violently flare when they are young, but my understanding was that they are supposed to calm down after a few billion years – that Kepler-438 is still violently flaring at 7 billion years old seems to suggest it is a bit more violent than others. If a red dwarf does settle down, it is feasible that a planet around it could redevelop its atmosphere from outgassing. So if anything, we’re going to want to study planets around red dwarfs of all different ages and activity levels so we can compare them and figure out the limits of habitability there.

  • Andrew LePage November 18, 2015, 14:53

    Even without this issue of atmospheric stripping by super-flares (an unresolved issue affecting many Earth-sized red dwarf planets), I felt that the prospects for the habitability of Kepler 438b were somewhat overstated when its discovery was announced in early January. Its mean stellar flux is about 3/4 that of Venus and it orbits outside the more conservative definitions of the habitable zone, contrary to the claims made by some:


    Except under some pretty contrived conditions, Kepler 438b is more likely to be a slightly larger and cooler version of Venus than a habitable world. Still, in the end more observations of the atmospheric conditions of this world will be required to confirm or refute the predictions made by any of the models.

  • lepton November 18, 2015, 15:03

    > Meanwhile, in the Rest of the Galaxy…

    This is on par with the bone scene in 2001.

  • Michael November 18, 2015, 15:37

    Although these M types are Star are violent and can strip away an atmosphere atmospheres are constantly been replenished provided there is enough tectonic activity. Mars been a small world could not keep up with the loss but a larger Earth massed world could.

  • Charlie November 18, 2015, 15:53

    I just wanted to give some added commentary to your story on photography. The reason why I was insistent on asking about the actual color images of Pluto (in this case) was that I find it very easy to be deceived by the subtle colorations that I and so many space photographs. I noticed that most celestial bodies photographed either by astronauts that actually went there, or by fly-bys space probes tend to be mostly uniformly grayish in coloration.

    The exceptions here on lot of the planets are Neptune, Uranus, Jupiter, Saturn, the earth, Mars. Each of these planets that I mentioned have sufficient coloration that the human eye can distinguish with fair degree of ease exactly what we would say would be the true coloration.

    The distance photographs that were taken of the planet Pluto on the other hand, is of such a nature that it’s HARD to exactly what they are even without any filters. I understand that the filter rations is being used to bring out or suppress certain wavelengths and all that business, but I still find do that in the case of Pluto. I’m still not sure exactly what it is, I’m looking at even in the UNFILTERED STATE. Can someone tell me would that be considered to be a tan coloration ? I wouldn’t think from that distance that that would qualify as gray , would others feel that it was more of a grayish coloration or tan ? But now at least you understand why I have been asking rather detailed questions on pictures that have been sent back on Pluto. To me they go overboard on providing too many filtered pictures which can be confusing to the reader who just wants to get a simple idea to start with about what it is that they are investigating.

    Getting back to the original fellow that did the first photographs, Mr. Gilster , are you saying there in the paragraph that you showed the un-retouched ‘photograph’ that that this gentleman had created a ‘un-retouched plate?’. And that the immediate image below is after he had washed it with the lavender oil and that brought out the image ? I’m confused by what you were saying in your paragraph there, could you please amplify what you were saying there?

  • Paul Gilster November 18, 2015, 16:13

    Charlie, the University of Texas site I quote (and link to) in the article is the best place for background on the image. The ‘unretouched’ version is what it looks like today until we process the image to bring it out more fully. We don’t have any images of what it looked like in his time, I’m afraid.

    So no, the ‘unretouched’ version is not what he produced before he washed it and brought out the image. It’s just what it looks like today to the naked eye.

  • Ashley Baldwin November 18, 2015, 19:28

    Planetary magnetic field strength depends on the presence of a partial liquid iron core ( 150% Earth sized seeming optimum) and planetary size up to 2 Earth mass ( Gaidos 2010) and planetary rotation( Zuluaga et al 2011) , with rates of below 2.5 days critical. After that field strength falls precipitously ( worse for 1-1.5 Mass Earth ) and field duration falls from an impressive ten billion years for a one day rotation for a 2Mass Earth to almost zero by a week . Leconte has shown that for 0.5-0.7 M sun stars a large proportion of the habitable zone will be close enough go be tidally affected and leading to planetary synchronous rotation. For a star of Kepler 438’s age that is over a month. However (Leconte 2014) has shown that even a relatively thin 1 bar atmosphere can help reduce this effect with increasingly thick atmospheres driving up rotation away from synchronicity. Plate tectonics drive vulcanism which in turn creates “secondary atmospheres” that can replace those lost to stellar activity on top of protection afforded by a magnetic field. The optimum mass for this is about twice Earth. In addition to having more internal heat to drive vulcanism such a planet will have greater gravity with which to hold onto its atmosphere . After 2 Mass Earth , increased density and internal pressure lead to a viscous , ” stagnant ” mantle and no tectonics. So vulcanism , thick atmospheres and magnetic fields can all resist stellar activity for the necessary billions of years under ideal conditions. Kepler 438b as stated is at the inner edge of the habitable zone so all those effects withstanding it is still likely to be uninhabitable due to runaway greenhouse and tidal heating. But stellar activity ,even with active M dwarfs, doesn’t preclude habitability if a planet can sit out the storm under its force field and thick atmospheric blanket.

  • Alex Tolley November 18, 2015, 23:59

    I’m not sure of the logic behind “seeing an object as if with unaided eyes”. As Plato’ Cave suggested, we see everything through distorting filters. Our eyes see only certain colors (if color blind fewer), and our brains transform those signals too. Having pictures that enhance features and colors shouldn’t be viewed as distorting “reality”. Almost any astronomical object we have public images of is not how we would see it. Perhaps scientists involved in the microscopic have less concern over this, as there is no unaided seeing, so that any image mediated by an instrument is a construct.

    One can just imagine the photograph “View from the Window at Le Gras” being further enhanced with color to try to show the color of the sky and the buildings. One’s view about that will depend on what one wants to see in such a photograph.

  • Harry R Ray November 19, 2015, 10:29

    Andrew LePage: That’s why it is extremely important to check for an atmosphere at Gliese 1132b! If there IS one(which I seriously DOUBT), CME atmosphere stripping would almost certainly NOT be a factor at Kepler 438b, which is much farther away from its parent star than Gliese 1132b is, and much cooler(at the cloud tops AT LEAST), and therefore would MOST LIKELY resemble Venus. NO atmosphere at Gliese 1132b would imply a POSSIBILITY, at least, that Kepler 438B is, instead, a Super-Mars with Mercury-like temperatures at the stellar point(assuming tidal locking), and extreme cold at the anti-stellar point, which COULD favor the scenario I put forth in my earlier comment.

  • Mark Zambelli November 19, 2015, 13:01

    Paul pointed out…
    “We don’t have any images of what it looked like in his time, I’m afraid.”

    Had to chuckle a bit there when I conjoured-up the mental-image that the second photograph ever taken was a pic of the first photograph ever taken! Reminds me of the old joke about Alexander Graham Bell… he was a genius not for inventing the first telephone, but for inventing the second telephone.

    On a serious note… Charlie, I can appreciate what you say about ‘false colour images’ not being what you’re after. These images are chock full of colour data that speaks volumes about the material composition etc of the subject, be that Mars, Pluto, what have you. Even our grey old Moon shows a wealth of colour if you simply up the colour saturation as I did here on one of my DSLR images… https://flic.kr/p/4hrySD .

    Add to the mix personal taste and it gets even more varied. There are many image processors who love assembling mosaics etc of any and all space imagery coming down from all over the solar system and as can be seen when 10 people have a go, you’ll get 10 different images. Some you’ll intuitively feel are better than the others. White Balance also causes headaches for processors trying to acheive that ‘natural to our eyes’ look and it is the reason colour swatch charts are in the frame when you look at images coming from our landers on Venus, the Moon and Mars… we know what the orange square, for example, should look like so the image is adjusted/corrected until the square looks orange.

    As has already been mentioned, what you ‘see’ shouldn’t be considered the absolute truth. There are many different ‘real’ images of a single subject and while they will differ, no one image is less real than another. Our eyes see in millions of shades of grey while our technology has improved from 2 bit images, through 8bit and up. 256levels of grey has rocketed to 65,536 levels with Photoshop regularly handling my 16 bit images.

    The best bet would be to read the image captions and ferret-out those images that have been processed to give a ‘natural as possible’ view, trust to it and bask in the wonders. Oh and I personally think ‘tan’ was a good description for Pluto in that image mentioned above.

  • Michael November 19, 2015, 13:12

    I am just wondering what would happen to a CO2/N rich atmosphere that shrouds a HZ world that has a lot of water. At first the primary atmosphere H/He would be lost and then the CO2/N one. Now would the water not be eradiated by the UV emission and break down to form Hydrogen which would then escape and leave a somewhat Oxygen rich atmosphere with an Ozone layer.

  • Michael November 19, 2015, 15:50

    Found the paper,


    It states some worlds can have substantial oxygen envelopes.

    Even stranger certain Stars can have oxygen atmospheres but alas gravity is a little steep, I wonder if after trillions of years cooling down they could accumulate water on their surfaces as well as oxygen.


  • Ashley Baldwin November 20, 2015, 14:36

    All of the above excellent comments just go to show that even with a potentially unfavourable case like Kepler 438b there is still ways of conceiving the presence of life . I have to admit that Mars doesn’t excite me as much as it dies others and much of the attention it gains is due the convenience of proximity and a solid surface , but the bottom line as pointed out is that if conditions were ever more favourable there , even if only for a short time as now seems likely , the experience of our sample size of one , Earth , is that when water and suitable energy coexist then life arises quickly and can persist through the most challenging of circumstances . The discovery of one novel microbe, different chirality or not and the whole equation changes for ever. I’m extremely disappointed that the Enceladus Life Finder, ELF, wasn’t short listed for the latest Discovery programme ahead of yet more asteroid missions and yet more Venus missions. How many do we need ? After Mars Enceladus is the best bet of discovering life without having to pull off mind boggling engineering feats of drilling through miles of ice on Europa whilst bathed in deadly radiation. I think it is likely that bio signatures will be found sooner on nearby planets by an ELT or the 2030s HDST than life on Europa, however likely it might be deep down in the icy depths . Enceladus genially brings it to us . It’s the long journey times that do for these outer solar system missions as Nasa want/need quick results and publicity to justify budgets at a difficult time . Alan Stern has to be congratulated for single handedly driving New Horizons through by force of will alone almost . For a few hours of science. Will Nasa try to get Congress to fund the use of SLS for such missions and thus make them viable ? The innovation is there it’s just the journey time that scuppers ELF,TiME and co. It was them who so wanted the SLS after all !

  • Nixak November 20, 2015, 20:19

    Kepler 438B- A Rare-Earth Reality Check:

    IMO the fact that Kepler 438b orbits its RED-Dwarf star in just 35 days should have been a dead give-away it almost certainly was more Mercury-Venus like than ‘Earth-like’. If Kepler 438b’s yr was only 1/10th that of Earth’s, that implies it was likely at-least 10Xs closer to it RED-Star than Earth is to the Sun [= 1AU] if it’s orbital speed approx = Earth’s [if twice as fast- it would likely be 5Xs closer]. That would mean radiation from Kepler 438b’s RED-star is up-to 25Xs – 100Xs more intense than if it were 1AU away.

    A planet that close to its star is almost certainly tidally-locked [which creates its own set of problems for habitability- flares or NOT], & the star’s solar-winds plus its massive [& regular] corona-flare bursts would strip it of its atmosphere [especially if it lacked a strong magnetic field-shield].

    IMO the real lesson of Kepler 438b is that [in general] red-stars’ planets should NOT be seen as good candidates for habitability.

  • Andrew LePage November 21, 2015, 13:33

    @Nixak November 20, 2015 at 20:19

    Your reasoning for concluding Kepler 438b is not habitable is seriously flawed and your calculation of its “mean radiation” (what is actually referred to as mean stellar flux or insolation) is just plain wrong. You can not conclude anything about the potential habitability of a world based solely on its orbital period and you can not calculate the mean stellar flux of a world from the orbital period without taking into account the mass and luminosity of the star in question.

    The orbital radius, a, of a planet orbiting a star with mass, m, is NOT proportional to its orbital period, P, as you claim. According to Kepler’s Third Law, a^3 = mP^2 (where a is in AUs, P is in years and m is in solar mass units). In the case of Kepler 438b, it has an estimated orbital radius of 0.166 AU according to its original discovery paper. If it were orbiting the Sun at that distance, it is true that Kepler 438b would have a mean stellar flux 36 times that of the Earth. But the star Kepler 438 has only about 3.9% the luminosity of the Sun (owing to its smaller radius and lower surface temperature) so the mean stellar flux is actually only 1.40 times that of the Earth not “up-to 25Xs – 100Xs more intense” as you claim.

  • Nixak November 22, 2015, 12:35

    @ A.LePage:

    Firstly you misunderstood what I said re: the intensity of radiation flux Kepler 438b gets from its own parent star. I said that if Kepler 438b were 0.1 AU away from its own star, the radiant intensity it would get from THAT star [NOT our Sun] would be 1/[(0.1)^2] = 100Xs [FYI: radiant intensity is equivalent to 1/(r^2), with r = the dist between the light-heat source & the location getting that light & heat] – thus 1/[(0.1 Au)^2] = 100Xs more intense than if were 1AU away from ITS OWN Parent star [NOT our Sun]. But now that you’ve informed me that Kepler 438b is actually 0.166Au away from its own parent star that means it actually gets 36.3 Xs more radiation intensity from its own star than it would if it were 1AU away from THAT star [NOT our Sun].

    But Of course a red-dwarf star generates far less heat & light power & intensity that a Sun type star, which is why you’d have to move the planet in question in so much closer to such a star- because a red-dwarf’s HZ is much closer to it than our own Sun’s HZ is to the Sun. But when you do that you significantly increase the odds that planet will become tidally-locked in such a close orbit to its star [become a so-called ‘eye-ball’ planet], as well as greatly increasing the risk that it get blasted by a red-star’s massive intense solar flare eruptions- especially if that happens frequently- which turns out that’s exactly the case re Kepler 438b!

    – 2nd: Yes a planet’s orbital period is indeed related its radial distance from its star. The dist a planet travels to make 1 complete orbit = 2(pi)r [r = the dist the planet is from its star]. The time it takes to make 1 complete orbit = its orbital speed / 2(pi)r. Thus one can calculate its aver orbital speed if you know the length of that planet’s yr [= 35 Earth days] & the distance it is from it star [per you = 0.166AU – Note: 1 AU = 93 Million mi / 150 million km] . thus Kepler 438b’s orbital speed = [2*3.1416{=pi}*(0.166AU) / 35 days] = [6.2832*0.166*93 million mi / 35*24hrs] = [97 million mi / 840 hr] = approx [0.1155 *10^6 mph] or 115,476 mph = what I calculate Kepler 438b’s average orbital speed is- assuming it’s 0.166AU from its red-star. Of course its orbital period [35 Earth days] = the dist it travels to make 1 complete orbit [=2(pi)r {r = dist it is from its star] divided by its orbital speed.

  • Andrew LePage November 23, 2015, 19:13

    @Nixak November 22, 2015 at 12:35

    Instead of arguing in circles about who is misunderstanding whom and why your calculation of the mean stellar flux of Kepler 438b is incorrect, you can read the preprint of the discovery paper (Guillermo Torres et al., “Validation of Twelve Small Kepler Transiting Planets in the Habitable Zone”) for yourself here:


    It clearly states that the mean stellar flux of Kepler 438b is 1.40 times that of the Earth not the figure(s) you claim.

  • Nixak November 24, 2015, 0:07

    @ A.LePage: But of-course 4% of 36.3 = 1.44Xs the amount of solar flux than Earth’s.

  • Nixak November 24, 2015, 5:33

    @ A.LePage PS: Yours is an ‘ironic’ choice of terms re: ‘arguing in circles’, since planetary orbits are basically all about- ‘Going Round in Circles’.

  • Eniac November 24, 2015, 21:23


    For a time, Kepler-438b looked so intriguing from an astrobiological standpoint, especially with its small radius 1.1 the size of Earth’s, but it takes an optimistic assessment of the habitable zone indeed to include it in the first place, and it now appears that the chances for life here are remote.

    This may or may not be true for Kepler-438b, but it certainly does not apply to Red Dwarf planets in general. As it says in the passage you quote:

    Following on from this, Lammer et al. (2007) concluded that habitable exoplanets orbiting active M dwarfs would need to be larger and more massive than Earth, so that the planet could generate a stronger magnetic field and the increased gravitational pull would help prevent atmospheric loss.

    So, we only need to look for slightly larger planets, which, for all we know, are at least as common as Earth-sized ones.

  • Nixak November 25, 2015, 7:29

    When you increase the size & mass of the planet, you MIGHT increase its magnetic field strength to better keep its atmosphere from being stripped away from the solar winds & powerful flare eruptions from its parent red-star, But- Say the planet’s radius is 1.5Xs Earth’s w a mass of maybe 3 – 3.5Xs Earth’s. Its gravity would perhaps be about 1.5Xs that of Earth’s- which means every macroscopic object including complex life-forms would be 1.5Xs heavier than they would be on Earth [assuming their masses remain constant]. Also water & blood pressure, would be 1.5Xs as great, & possible even its atmospheric pressure too [but there are other factors that affect air-pressure]. This would affect how large animal type life forms could get, how they’re built- IE: needing a lot more muscle & bone strength & density.
    Yet there’s a much bigger issue than that: Water Vapor has a molecular weight [MW] of 18, while ammonia’s MW = 17 & methane’s MW = 16. This implies the planet’s gravity would have to be ‘fine-tuned’ within at-least 1-2 parts in 18 of Earth’s gravity to hold on to its water-vapor yet dissipate most of its toxic ammonia, & toxic & highly flammable methane- which is also a very potent GHG gas [35Xs – 100Xs more than CO2]. IMO a planet whose gravity is 1.5Xs Earth is just NOT close enough to 1-2 parts in 18 of Earth’s gravity. So that planet would likely have a build-up of the powerful GHG gas methane in its atmosphere- thus triggering a run-away green-house effect, which could vaporize much/most/all of its surface liquid [& ice] water, which water- vapor itself is a GHG gas- Resulting in most of the planet’s liquid water vaporizing into its atmosphere & from there perhaps even dissipating into space. The End Result would likely be more Venus-Mercury like than Earth-Like.

    There are multiple reasons Red-dwarfs in general are not good parents for hosting life-bearing planets:
    – HZ too close to the star.

    – This means bringing the planet in so close it would likely be tidally-locked & become a so-called ‘eyeball planet.

    – Also its closeness would bring it within range to get blasted by the Red-Dwarf’s powerful solar-flare eruptions [ala Kepler 438b]

    – If you significantly increase the planet’s size & mass to generate a strong enough magnetic field shield to protect its atmosphere, you risk building up too much methane, that could trigger a run-away green-house affect.

    – Red-dwarfs’ dimness & red-spectrum light is NOT ideal for photosynthesis.

  • Eniac November 26, 2015, 1:25

    Nixak: A larger planet will retain atmosphere better mainly because of gravity, only secondarily because of magnetic field. A dense atmosphere will equalize temperatures around tidally locked planets. 1.5 times gravity will make little difference in how large lifeforms can get, and has no impact on smaller life. Your theory about fine-tuning gravity for atmospheric composition is misguided. Getting “blasted” by solar eruptions will have no effect at the bottom of a dense atmosphere. Even Earth’s relatively tenuous atmosphere is dense enough to block all ionizing radiation from space, except for some muons from high energy cosmic rays.

  • Nixak November 26, 2015, 20:26

    @ Eniac: If a man weighs 220lb /100 kg on Earth & gets transported to the planet w 1.5Xs Earth’s gravity, he’d then weigh 330 lbs / 150 kg. Are you saying that would absolutely make NO difference re: how his body structure would [have to] develop [a 6ft-5in man at 220lbs is NOT considered over-weight, but at 330lbs he’d be quite morbidly obese]? I’m not saying that could NOT be compensated for, but IMO it would be a significant constraining factor.

    Yeah a dense atmosphere would equalize surface temps on a tidally locked planet, that’s indeed what happened on Venus & we see how that turned out.

    I disagree that a planet w 1.5Xs or more Earth’s gravity is a none factor re: holding on to its water vapor, yet being able to dissipate most of its atmospheric ammonia & methane gas- & if there is a significantly large methane gas build-up in its atmosphere it would not only be toxic [might possibly be compensated for, especially re microbe type life-forms], but also likely quite volatile in the presence of O2, & would almost certainly trigger a run-away green-house effect. But IMO we’ll eventually see if this is indeed so, or no.

  • Nixak November 26, 2015, 20:42

    @ Eniac- PS Further to the above: You need a strong enough magnetic field-shield to protect on in close [likely tidally-locked] planet’s upper atmosphere from be stripped away by its red-dwarf star’s regular intensely-powerful solar-flare eruptions. This is indeed what happened to Kepler 438b.

    Such solar flare eruptions would likely regularly trigger lightning storms in the planet’s atmosphere. But if there’s a lot of methane plus O2 gas present- BOOM!!!

  • Alex Tolley November 26, 2015, 22:16

    @Nixak You are thinking in land surface terms. Gravity makes almost no difference for aquatic animals, which is why whales can attain such large sizes, as well as some fish like the Pliocene Megalodon shark.

  • Nixak November 27, 2015, 9:53

    @ A.Tolley: Note that Water Pressure would also increase by a factor of 1.5Xs of that on Earth.

    But again- That’s NOT even the main issue. If too much toxic-volatile methane gas builds up in the planet’s atmosphere because its gravity is +1.5Xs or more than Earth’s, that would likely trigger a run-away green-house effect, that would evaporate most/all that planet’s surface water- making aquatic animal-life [or just about any type conceivable of complex macroscopic life-form] a NON-Starter.

  • Alex Tolley November 27, 2015, 12:29

    I think you are mobving the goalposts. I was responsing to your comment:

    If a man weighs 220lb /100 kg on Earth & gets transported to the planet w 1.5Xs Earth’s gravity, he’d then weigh 330 lbs / 150 kg. Are you saying that would absolutely make NO difference re: how his body structure would [have to] develop [a 6ft-5in man at 220lbs is NOT considered over-weight, but at 330lbs he’d be quite morbidly obese]? I’m not saying that could NOT be compensated for, but IMO it would be a significant constraining factor.

    You compound it with this:

    Note that Water Pressure would also increase by a factor of 1.5Xs of that on Earth.

    Marine organisms live in a pressure range of 1 atm to over 1000 atm in the ocean trenches. Lithospheric microorganisms live in much greater pressures. A mere 1.5x pressure change is insignificant.

    Atmospheric effects on temperature may be more significant, but your intuitions about the effects of gravity and pressure on organisms is wrong. Ii I may be so bold, I think you have taken ideas about size, weight and strength relationships for humans and used these to color your thinking, rather than seeing how life would evolve based on environmental and physical constraints.

    My personal belief is that we need to understand a lot more about life’s origins in determining whether worlds are life bearing or not. It may well be that if life is deliberately introduced to dead worlds, that it will likely flourish if conditions are suitable. In practical terms, I think that Europa and Enceladus are likely sterile, but that we could make their subsurface oceans living by introducing [gene engineered] organisms suitable to those environments.

  • Eniac November 29, 2015, 1:57


    If a man weighs 220lb /100 kg on Earth & gets transported to the planet w 1.5Xs Earth’s gravity, he’d then weigh 330 lbs / 150 kg. Are you saying that would absolutely make NO difference

    No, but I am saying that it makes little difference with respect to the possibility of life. On the 1.5X planet, that man would either be more muscular or smaller. There is plenty of room for both, as the presence of both larger and smaller animals on Earth demonstrates. The same goes for hydrostatic pressure, as Alex has said. The range suitable for life is enormous, and a 1.5X increase will not make a dent in that.

    There is no need for ammonia or methane to escape into space. They could just as well be fixated (biologically or geochemically) or oxidized, or both. Indeed, this is what happened on Earth, I believe. N2 and CO2 are the oxidation products of ammonia and methane, and the CO2 has all been fixated into biomass, fossil fuels, and limestone.

  • Eniac November 29, 2015, 2:15


    My personal belief is that we need to understand a lot more about life’s origins in determining whether worlds are life bearing or not.

    Given the utter inaccessibility of the origin of life to observation, I fear our education will proceed the other way, i.e. by finding (or not finding) life-bearing worlds we will learn something about life’s origin.

    My personal belief: Not finding, most likely, and what we’ll learn from that is that abiogenesis is rare. We could have guessed that…

    We can hope I’m wrong, though. How wonderful it would be to find another form of life to study!

  • Eniac November 29, 2015, 14:55


    You need a strong enough magnetic field-shield to protect on in close [likely tidally-locked] planet’s upper atmosphere from be stripped away by its red-dwarf star’s regular intensely-powerful solar-flare eruptions. This is indeed what happened to Kepler 438b.

    I do not think there is actual evidence that this happened to Kepler 438b. It is merely speculated that it might happen, and it is clear and obvious that it would happen much less on a larger planet. Look up “Jeans escape” to learn more about the effect of gravity on atmospheric escape.

    Such solar flare eruptions would likely regularly trigger lightning storms in the planet’s atmosphere. But if there’s a lot of methane plus O2 gas present- BOOM!!!

    Here you have yourself identified one reason why methane might be absent in an atmosphere even without being lost into space.

    Except for the lightening part. Lightening is caused by atmospheric storms, not solar storms. Yours is, to my knowledge, the first speculation that space weather can cause Earthly lightening, and I am taking it with a huge boulder of salt.

  • Alex Tolley November 29, 2015, 17:21

    @Eniac – I agree. The most likely scenario, IMO, is that we will detect bio-signatures of terrestrial like life on exoplanets, while finding none elsewhere in the solar system (or at least where we have managed to search in the next few decades).

    This means that astrobiologists we will be in the frustrating position of having evidence of life elsewhere, but no way to study it up close. No conceivable telescope will be able to help either. We will need probes to study those living worlds in detail, particularly for understanding the molecular and biochemical similarities and differences.

    If by a long shot we discover life in the plumes of Enceladus or Europa, or even in subsurface Mars, a sample return mission will be called for to bring back that life for study. It would be a goldmine of information and possibly new wealth opportunities. (And astrobiology would no longer be a theoretical science).

  • Nixak November 29, 2015, 22:56

    @ Eniac:
    The current prevailing theory is that initially on Earth, both atmospheric N2 but especially CO2 were produced by Volcanic out-gassing.
    Also note Gas & Ice giants have plenty of ammonia in their atmospheres while Titan has methane lakes & a N2 & methane based atmosphere [@ 95% – 98% N2, & 1.5% – 5% CH4]. Of course none of this is due to biological activity.

    IMO we should refrain from using biology as a legit explanation for setting the right initial conditions for planetary habitability, when we’re looking for the right initial conditions to support the development of life to begin with.

  • Michael November 30, 2015, 1:12


    ‘Except for the lightening part. Lightening is caused by atmospheric storms, not solar storms. Yours is, to my knowledge, the first speculation that space weather can cause Earthly lightening, and I am taking it with a huge boulder of salt.’

    They are speculating here that cosmic rays, space weather, can cause lightning on Earth. I find it fascinating that lightning can cause gamma rays!


  • Eniac November 30, 2015, 19:47

    @Nixak: Some planets have a reducing atmosphere, meaning plenty of ammonia, methane, hydrogen, what have you. No oxygen can exist, there. Earth has a fully oxidized atmosphere, including molecular oxygen. No hydrogen, ammonia, or methane can exist, there.

    Earth has become this way because of life, but these are certainly not the right conditions for the development of life. Life most likely originated under reducing conditions, such as those on Titan. Oxygen is a deadly poison that Earth life had to adapt to after photosynthesis began and the oceans, crust and atmosphere slowly became oxidized.

  • Nixak November 30, 2015, 21:43

    @ Michael:

    It was I, NOT Eniac, who stated a nearby planet being regularly blasted by its red-Dwarf star’s regular & powerfully intense solar-flares would likely trigger lightning in its atmosphere, if it lacks a strong enough magnetic field-shield to sufficiently protect its atmosphere. And if its methane levels are hi enough in the presence of O2, this would likely trigger atmospheric explosions in the vicinity of those lightning discharges.

    Why? Because even on Earth there’s upper atmospheric lightning. The Aurora lights are triggered by charged particles from the Sun’s solar-flare activity, but Earth’s magnetic field-shield is strong enough to keep those discharges hi up in the upper atmosphere. In fact even Venus at-times has some strong lightning discharges in its very dense atmosphere.

    Also there appears to be a link between cosmic rays & cloud formation on Earth: From PhysicsWorld.com; Physicists claim further evidence of link between cosmic rays and cloud formation: A Danish group that has reproduced the Earth’s atmosphere in the lab, has shown how clouds might be seeded by incoming cosmic rays… Dr H.Svensmark’s group has studied how the energetic particles reaching Earth from space, aka cosmic rays, can influence the planet’s climate as a result of changes to the Sun’s output. The idea is that cosmic rays seed clouds by ionizing molecules in Earth’s atmosphere that draw in other molecules to create the aerosols around which water vapour can condense to form cloud droplets… [see @ http://physicsworld.com/cws/article/news/2013/sep/09/physicists-claim-further-evidence-of-link-between-cosmic-rays-and-cloud-formation ]
    Of course such cloud formation is linked to lightning discharges in Earth’s lower atmosphere.

  • Nixak November 30, 2015, 21:53

    @ Eniac: O2 is what made the advent of animal life-forms including human-life even possible here on Earth [post Cambrian Explosion]! Cause O2 is what we & nearly all types of animals breath to facilitate our metabolism- NOT H2, ammonia, Nor methane!

    O2 might be a so-called ‘deadly poison’- but try breathing without it!!!

  • Nixak November 30, 2015, 23:45

    PS @ Eniac:

    Yeah such lightning strikes in a planet’s atmosphere w hi levels of methane & O2, would initially be quite volatile but the by-products of such ‘BOOMS’ would be water vapor & CO2. YET both are also GHG gases, just NOT as potent as methane. But w its red-dwarf star’s HZ being so close that the planet would likely be tidally-locked, such that even w the planet’s atmosphere now being laden w CO2 & water-vapor [instead of methane + O2], it still would risk a run-away green-house effect- IE: could still look more like Venus than Earth.