Exoplanets: How we’ll search for signs of life

Arizona State University

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IMAGE: On the left, the oxygen-producing biosphere (photosynthesis/respiration) is fed by nutrient runoff from land. On the right, if you increased water on Earth enough to cover all land, then nutrient… view more  Credit: D. Glaser/ASU

Whether there is life elsewhere in the universe is a question people have pondered for millennia; and within the last few decades, great strides have been made in our search for signs of life outside of our solar system.

NASA missions like the space telescope Kepler have helped us document thousands of exoplanets – planets that orbit around other stars. And current NASA missions like Transiting Exoplanet Survey Satellite (TESS) are expected to vastly increase the current number of known exoplanets. It is expected that dozens will be Earth-sized rocky planets orbiting in their stars’ habitable zones, at distances where water could exist as a liquid on their surfaces. These are promising places to look for life.

This will be accomplished by missions like the soon-to-be-launched James Webb Space Telescope, which will complement and extend the discoveries of the Hubble Space Telescope by observing at infrared wavelengths. It is expected to launch in 2021, and will allow scientists to determine if rocky exoplanets have oxygen in their atmospheres. Oxygen in Earth’s atmosphere is due to photosynthesis by microbes and plants. To the extent that exoplanets resemble Earth, oxygen in their atmospheres may also be a sign of life.

Not all exoplanets will be Earth-like, though. Some will be, but others will differ from Earth enough that oxygen doesn’t necessarily come from life. So with all of these current and future exoplanets to study, how do scientists narrow down the field to those for which oxygen is most indicative of life?

To answer this question, an interdisciplinary team of researchers, led by Arizona State University (ASU), has provided a framework, called a “detectability index” which may help prioritize exoplanets that require additional study. The details of this index have recently been published in the Astrophysical Journal of the American Astronomical Society.

“The goal of the index is to provide scientists with a tool to select the very best targets for observation and to maximize the chances of detecting life,” says lead author Donald Glaser of ASU’s School of Molecular Sciences.

The oxygen detectability index for a planet like Earth is high, meaning that oxygen in Earth’s atmosphere is definitely due to life and nothing else. Seeing oxygen means life. A surprising finding by the team is that the detectability index plummets for exoplanets not-too-different from Earth.

Although Earth’s surface is largely covered in water, Earth’s oceans are only a small percentage (0.025%) of Earth’s mass. By comparison, moons in the outer solar system are typically close to 50% water ice.

“It’s easy to imagine that in another solar system like ours, an Earth-like planet could be just 0.2% water,” says co-author Steven Desch of ASU’s School of Earth and Space Exploration. “And that would be enough to change the detectability index. Oxygen would not be indicative of life on such planets, even if it were observed. That’s because an Earth-like planet that was 0.2% water–about eight times what Earth has–would have no exposed continents or land.”

Without land, rain would not weather rock and release important nutrients like phosphorus. Photosynthetic life could not produce oxygen at rates comparable to other non-biological sources.

“The detectability index tells us it’s not enough to observe oxygen in an exoplanet’s atmosphere. We must also observe oceans and land,” says Desch. “That changes how we approach the search for life on exoplanets. It helps us interpret observations we’ve made of exoplanets. It helps us pick the best target exoplanets to look for life on. And it helps us design the next generation of space telescopes so that we get all the information we need to make a positive identification of life.”

Scientists from diverse fields were brought together to create this index. The formation of the team was facilitated by NASA’s Nexus for Exoplanetary System Science (NExSS) program, which funds interdisciplinary research to develop strategies for looking for life on exoplanets. Their disciplines include theoretical and observational astrophysics, geophysics, geochemistry, astrobiology, oceanography, and ecology.

“This kind of research needs diverse teams, we can’t do it as individual scientists” says co-author Hilairy Hartnett who holds joint appointments at ASU’s School of Earth and Space Exploration and School of Molecular Sciences.

In addition to lead author Glaser and co-authors Harnett and Desch, the team includes co-authors Cayman Unterborn, Ariel Anbar, Steffen Buessecker, Theresa Fisher, Steven Glaser, Susanne Neuer, Camerian Millsaps, Joseph O’Rourke, Sara Imari Walker, and Mikhail Zolotov who collectively represent ASU’s School of Molecular Sciences, School of Earth and Space Exploration, and School of Life Sciences. Additional scientists on the team include researchers from the University of California Riverside, Johns Hopkins University and the University of Porto (Portugal).

It is the hope of this team that this detectability index framework will be employed in the search for life. “The detection of life on a planet outside our solar system would change our entire understanding of our place in the universe,” says Glaser. “NASA is deeply invested in searching for life, and it is our hope that this work will be used to maximize the chance of detecting life when we look for it.”

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From EurekAlert!

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72 thoughts on “Exoplanets: How we’ll search for signs of life

  1. Whaddaya mean, our place in the universe? Our place is right here. It’s not as if we’re ever going to be able to leave.

    Is this what NASA is doing right now, besides ginning up evidence of global warming? For a long time now, NASA has looked suspiciously like a bunch of smart people doing smart things that have no substantive value. They sent men to the moon to install a plaque bearing the words, “Richard Nixon,” and that was pretty much most of the show right there. Everything else has been a denouement.

    • ” It’s not as if we’re ever going to be able to leave.”

      Mankind will definitely leave this planet and travel to other solar systems. The speed of light is a limitation only when your mind is closed by dogma. GR offers other possibilities. For example, the Alcubierre warp drive whose existence proof is the propulsion method of a photon.

      • Well, I hope you are right, but politicians continually find new and inventive ways to destroy our future. Leave the Planet? Right now, we are scarcely allowed to leave our houses!

      • The real limitation is surviving in a hostile space environment. Even leaving the Earth’s magnetic protection to travel to Mars looks difficult with actual discussions of whether we send men (who will go blind on the trip) or women (who will be more prone to cancer). And that’s within the Heliosphere. Venture outside of that and we suddenly enter a universe of harsh cosmic radiation and who knows what else.

        I love Star Trek and Star Wars and all kinds of interstellar travel fantasies. We have a lot of problems to solve before we get there, if we ever can.

      • Putting humans into a vessel traveling at the speed of light is the 2nd of many problems.

        There are so many problems to solve, the actual propulsion/bending space, human condition in zero gravity for long periods, external hostile elements such as radiation, collision with foreign space objects, transporting necessary supplies to the destination, so that someone can colonize said habitable planet, And quite probably surviving invasive species of germs, animals, vegetables and minerals or if they are advanced, applying for and receiving admittance and acceptance as illegal aliens from a possibly hostile species or at least a conservative species that doesn’t wish to see their neighborhoods go to shite.

        that people will still be debating it on comment boards when your body is fully decomposed.

        • Will any humans still be around on Earth in 300,000 years when the message comes back, “Have arrived safely. Met some nice blokes already. Invited us to a get-to-know-you party. Awaiting further instructions from base operations on Earth. Please respond soonest.”

        • Many of these problems also existed when the New World was ‘discovered’. The ones related to space travel will sort themselves out with technology. Regarding the others, since we will be the ‘greenhorns’ of interstellar space travel, we will be compelled to live by the rules of the others, of which there will be many. We’re closer to this than many think and there’s a lot of public and private dollars being invested in solving the interstellar space travel problem which we already know with absolute certainty is not impossible. Once we’re out there, we’ll be noticed, if it’s not already the case.

          • “…we will be compelled to live by the rules of the others, of which there will be many…” Again, Star Trek and Star Wars are entertaining fantasy. What concrete evidence do you have of the existence of any other technologically advanced space-faring culture in the universe. And no, the Drake Equation is neither concrete nor evidence.

          • Wayne,

            There was some recent video evidence released by the Navy that shows a craft who’s propulsion characteristics can only be explained as control over gravity, or more precisely, the local manipulation of space-time curvature.

            https://www.space.com/ufos-videos-declassified-navy-release.html

            Whether these craft are ours or belong to an ET, it’s exactly the kind of propulsion system required to cross interstellar space in reasonable times. The fact that they’re unaffected by inertia is a dead give away as that would be characteristic of isolating a craft in a sub-space that’s otherwise disconnected from the reference frame of the space-time it’s passing through, effectively hiding its mass from the Universe , thus infinite energy is no longer required to achieve the speed of light, or beyond. Within the craft, you are always weightless, unless similar techniques are used to create artificial gravity within it.

            It only took on the order of 100 million years for DNA to evolve and the initial conditions for its evolution are ubiquitous throughout the galaxy. We now estimate our galaxy to have a billion or more planets in the habitable zones of stars, so that’s a billion other places DNA could have evolved in the last 14 billion years or so. If DNA arrived by way of panspermia, then DNA is already everywhere. Either way, we are the existence proof that DNA readily emerges and that an intelligence capable of understanding the Universe emerges from DNA. Given a billion other places where this could also occur makes it extremely unlikely that we are alone. If forced to bet one way or the other, I’d definitely not bet on us being alone in the Universe, would you?

          • Forced to bet on proving a negative? That’s a no-win position. Either evidence arises of other life to prove you wrong, or you die not having been able to prove that none of the two trillion galaxies and 10^24 stars have a planet with life.

            But if forced to bet whether intelligent extraterrestrial life will be detected within the next thirty years, I would happily bet a large sum against the prospect.

          • Rich,

            How can you explain the flight characteristics of the crafts in the video? If we have technology that can do that, keeping the basic science classified is wrong, although if it is ours, they would have know where are planes are flying in order to keep a low profile, especially since the videos are from long scheduled exercises. The only other rational explanation is that it’s under the control of intelligent extra terrestrial life.

            If it is ours, then based on the flight characteristics of the craft, we’re already capable of being an interstellar species and if we can do it, then any random slime can evolve to do the same. Either way, you’ve lost the bet before you’ve make it.

  2. Life arose on Earth, or arrived here, when there was little land. Yet the first organism could have developed on that small area of land rather than under the sea. Both harbored environments capable of incubating life.

    • John,

      I’m leaning more and more towards Panspermia. While I can see the path of evolution from RNA to DNA, RNA, or perhaps a precursor, arose is a very short amount of time. We know that comets and/or asteroids contain amino acids and other complex organics and that such molecules, or tholins, are wide spread throughout our solar system where we’ve observed them as far away as Pluto. From this organic soup to RNA via solution in liquid water is a more comprehensible path, it’s also short enough that it’s extremely unlikely not to have already occurred somewhere else where liquid water is present. Even ʻOumuamua, which is the extra solar system object that passed through recently, is thought to have been covered in tholins, so we also know that organics can pass between solar systems and based on its velocity, it could have traversed the galaxy many times over showing that the migration of organics from anywhere in the galaxy to here and everywhere else is definitely possible.

  3. Yawn. Really. Double yawn. Coming up with a “detectability index” for exoplanets that are in reality millions of light years (or at the closest possible, hundreds of thousands of light years) away from us? I can think of better ways of putting government (or foundation/endowment) money to use – like putting all of these big brains into a room to think of ways to develop a vaccine for the COVID-19 virus.

    I am generally all for pursuing knowledge for knowledge’s sake. But because of the bees in many scientists’ bonnets and the obsession with government-imposed lockdowns, climate change, and other apocalyptic hysteria, I have become rather suspicious of the extent to which the scientific community avidly pursues this line of research. I smell a much larger ideological purpose to this that I fear is not necessarily to the benefit of mankind as a whole. The money spent on this project, while it may seem small by comparison to, say, climate research (another field where ideological, Lysenko-style science has taken hold) or military research, which fields of research can make a much more compelling case for their work and its net benefit to humanity, is not going to provide the kinds of net benefits to either our body of knowledge for its own sake or our humankind.

  4. Organisms contain DNA, RNA, and complex proteins. It is unlikely in the primordial soup that there would be the right sugars and amino acids to form the DNA helical molecule, let alone the RNA, and the complex proteins that make up a cell. And then to think that a membrane could form around those chemicals, seems impossible to me. On top of that, the inclination on earth is for things to decay, rather than to form complex substances.

    • The main reason things decay on Earth is that there are trillions of microrganisms around the place. Nobody (but the god zealots) believes that modern organisms with their extremely complex ‘design’ arose fully intact, but rather as a multi-step process from simple self-organising structures.

  5. Well no, co2isnotevil, the proposition that nothing with mass can exceed the speed of light is not dogma, but mathematical fact. I am vague about the General Theory of Relativity but I know the Special Theory of Relativity well, and can derive the Lorentz Transformation. (Which you can do with Grade 11 Math, incidentally.) Velocities greater than the speed of light result in the Transformation yielding an undefined value.

    So we ain’t gong anywhere, because there is nowhere to go that can sustain human life. Well, physical human life. There may be some variety of life that is not physical (like, after you die), but that’s an undiscovered country, isn’t it?

    • Granting you’re right, Ian, we can still move out by traveling in biospheres. A hollowed-out asteroid, for example.

      When we colonize the solar system, we will inherit riches in raw materials. If we have a fusion industrial power source, it seems likely that we will be able to modify planetoids, or to construct bio-arks.

      Even below the speed of light, colonization of the stars is possible.

      • Adaptation to low/no-gravity would forever alter those travelers and their subsequent generations. Unless you know of some new physics to create gravity fields without mass.

        • I’m inclined to agree with those who are skeptical of our ability to survive the harsh conditions of interstellar space, but artificial gravity can surely be created through rotation. You can’t produce a gravitational field without mass but you can subject a mass to a constant acceleration equal to the acceleration due to gravity.

          • The comment suggested buried inside an asteroid for shielding.
            But Asteroids are mostly heaps of rubble. Likely too mechanically weak to spin at the rates needed a few 1/10s of 1G on the inside without flying apart. Lots of asteroids spin, but at rates too low for any significant centripetal acceleration for someone on the inner surface.
            And iron-nickel core remnant asteroids, which might be mechanically rigid enough for high spin, would be prohibitively difficult to mine and then accelerate, decelerate.

          • How about excavation of a Ni-Fe body with nuclear devices, Joel? Or ablation with a seriously high-powered laser?

            Within 100 years or so I’d expect we humans will be able to deploy very large amounts of energy, tightly focused.

      • Some engineer please calculate how much uranium or thorium (as a percent of the total mass) would be needed to provide the power to move the quite large mass of an asteroid on path out of the solar system at a speed sufficient to get to get to the nearest earth-like planet in less than a million years.

        My guess is that even if it was 50%, that wouldn’t be enough. This is just another incarnation of the escape velocity fuel requirement problem.

    • “So we ain’t gong anywhere, because there is nowhere to go that can sustain human life.”

      Artificial habitats in space can sustain human life. Artificial habitats can supply artificial gravity equavalent to the gravity on the surface of the Earth, and can protect against dangerous radiation and can be large enough to accomodate millions of peole. That’s where most humans who leave Earth will be going, until we learn how to travel faster than light.

      The good news is we don’t have to leave the solar system to survive the Sun changing into a red giant. We can just move our artificial habitats a little farther away from the Sun as it expands. Although what the human race will look like that far in the future is anyone’s guess.

      • My wife and I just spent half a day repairing decorative shutter fasteners on our house. A couple of the screws we had were undersized for the job, so we’ll have to go to Home Depot tomorrow.

        The environment in Northern Virginia isn’t quite as hostile as interstellar space, especially at a single or double digit percentage of the speed of light. And in space, no one can hear you say “Home Depot.” How is a big, mobile bio-ark going to be maintained for centuries with no outside provisioning?

    • Ian,

      The speed of light limitation as it applies to interstellar travel is indeed dogma. How can you deny the preponderance of evidence that shows crafts exhibiting the kind of behaviors consistent with the General Relativity conforming theoretical warp drive. Having seen this, an explanation based in the laws of physics must be possible, we only need to accept the possibility and seek that explanation.

      I consider GR to be the grand unified field theory Einstein was seeking. On one side is space-time curvature and on the other is the stress-energy tensor. In principle, all manifestations of energy (i.e. existence) can be represented by a stress-energy tensor, thus is seems clear that space-time curvature is the more fundamental constituent of all existence and that the Universe’s opposition to being curved is what manifests the stress-energy tensor.

      The one complication is the singularity which I can make disappear by introducing a concept called Conservation of Curvature where all curved space-time is accompanied with an equal and opposite amount of uncurved space-time which leads to a quantification of particles (the uncurved space-time is on the inside of a particle) linking GR to Quantum Mechanics. BTW, this also removes the singularity of black holes which are just giant particles where the event horizon becomes the boundary between the curved space-time on the outside and uncurved space-time on the inside.

      The theoretical Alcubierra Warp Drive is a conserving function of space-time curvature which looks almost exactly like what my hypothesis proposes is the curvature signature of a photon manifesting its propulsion method. If a craft’s mass is enclosed by the region between the relatively curved and uncurved space-time, then the curvature of that mass (i.e. it’s gravity) is shielded from the space-time it’s traversing through. In principle, the region between the curved and uncurved space-time is a sub-space at a singular point in time.

      A photon exposes both its curved space-time and its uncurved space-time curvature to the Universe, effectively cancelling each other out relative to gravity. A particle exposes only its curvature to the Universe. The anti-curvature on the inside is hidden behind it’s surface of relative flat space-time (the particles surface) while the curvature on the outside manifests mass and gravity. Another important consideration is that this surface is a singular point in space-time independent of the speed of light and it’s apparent dimensions, the result of which manifests the Heisenberg Uncertainty Principle.

      https://phys.org/news/2017-01-alcubierre-warp.html

  6. “It’s easy to imagine that in another solar system like ours, an Earth-like planet could be just 0.2% water,” says co-author Steven Desch of ASU’s School of Earth and Space Exploration. “And that would be enough to change the detectability index. Oxygen would not be indicative of life on such planets, even if it were observed. That’s because an Earth-like planet that was 0.2% water–about eight times what Earth has–would have no exposed continents or land.”
    What effect would having 8 times more ocean on Earth, be?
    Are we certain, that Earth would have plate tectonic activity?
    With Earth, and whenever get super continent {one say we currently have super continent type situation, now}
    The oceans get deeper. Hmm not finding it, but related {and wild theories}, as in:
    ” The ancient supercontinent of Rodinia turned inside out as the Earth swallowed its own ocean some 700 million years ago, new research suggests.”
    https://www.livescience.com/64707-earth-swallowed-superocean.html
    And:
    https://www.express.co.uk/news/science/1139691/Ocean-sinking-Earth-mantle-oceans-consumed-dead-supercontinent-Pangea
    Anyways, I thought with supercontinents one has deeper oceans, but could not find ref to it. But above ref talk of “swallowed its own ocean” so if had more ocean, would it swallow more ocean. Or do have any plate tectonic if “land surface” are 30 km under the ocean.
    Or would earth’s mantel be as dry. Though if have soggy mantel, do get even more plate tectonics.
    Or maybe when have as much rock as Earth has, it can’t ever be submerged. Or plate tectonic is responsible bringing water to surface. So planet less geological active {less volcanic and/or less plate tectonic activity] water sinks back into interior. But if as geologically active as Earth {or more geologically active] it simply pushes land up, even if added say 40 times as much ocean. Or 40 times more gives a less dry {or soggy} mantel {and I guess you have much more explosive volcanoes}.

  7. “Anyways, I thought with supercontinents one has deeper oceans, “…

    Not necessarily, but certainly larger ocean/oceans as there would be one ocean stretching from one coast of the supercontinet around the planet to the other coast.

    Ther have been [or it is postulated that there have been] about 11 supercontinenets through the last 3.600 miilion years.
    https://en.wikipedia.org/wiki/Supercontinent

    • 70% of Earth surface {ocean floor} is at most, is about 200 million years old.
      The puzzle of Earth’s history has big pieces missing.

  8. Given the insane global Wuhan flu economic shutdown, and the growing popularity of Socialism, it seems intelligent life doesn’t exist on earth…

  9. I always worried that sticking an LP with a soundtrack including the Beatles on the side of Voyager would be taken by any intelligent life as a declaration of war.

  10. Why is the assumption made that life requires oxygen. Even here on Earth there are many species that not only do not require oxygen but it is actively toxic. Admittedly they are “only” bacteria but they are still life. It is not beyond the realms of possibility that higher life forms could evolve without the need for oxygen.

  11. We all remember the song from Monty Python’s Meaning of Life. …. intelligent life elsewhere in the universe because there’s bugger all down here on earth. https://www.youtube.com/watch?v=buqtdpuZxvk

    The way many keep falling for scare campaigns- hole in the ozone layer, catastrophic anthropogenic global warming, the COVID scamdemic which is just a slightly worse than usual flu is testament to how humans have evolved in to dung beetles. Dung beetles have evolved in to swallowing copious amounts of bovine excrement.

    We need to find those intelligent life forms and ask them how they got it right, because we have failed badly.

  12. “Without land, rain would not weather rock and release important nutrients”

    Funny.
    What about sea streams?
    Volcanos?

    • An active system of plate tectonics would be a definite advantage to a planet’s ecosystem, though I’m not sure how we’d look for it through a telescope.

  13. Thumbs down from me also.
    What the heck is the benefit of this expenditure, in a few words? Geoff S

  14. This appears to be yet another product of Ivory Tower academic mental master bait shun. So, they believe an entire planet of ocean bottom WON’T be eroded by ocean currents? They believe there will be no underwater volcanoes or smokers? Continental rifts?

    What planet are these guys from?

  15. NASA has no idea what life is. They believe that is you have all the ingredients the rest is magic. They believe like Darwin “Natural Selection” and all the time in the world will JUST DO IT. POOF LIFE naturally puts all the elements together by random chance with NATURAL SELECTION ( the magic). This is the worlds biggest example of completely disconnected science and scientists with more hubris then knowledge.

  16. Salute!
    Everybody keeps looking at the “planets”, and most we have found are fairly large or would not disturb the star or block enuf light.

    I am betting on Cameron’s idea of an Earth like moon orbiting one of those suckers. You know, like Pandora.

    And as far as never having the equivalent of “warp” drive, well then…

    Clarke’s First Law: When a distinguished but elderly scientist states that something is possible, he is almost certainly right. When he states that something is impossible, he is very probably wrong.
    “Hazards of Prophecy: The Failure of Imagination” in Profiles of the Future (1962)

    and then from the master

    “Any sufficiently advanced technology is indistinguishable from magic.”

    Imagine going back to your childhood, like the late forties in my case, and showing your grandma your iPhone, even without an internet connection. I was blessed to see electronics blossom and even built early transistor amplifiers and radios -think CK-722 and 2N-107.

    Gums sends….

  17. The search for life on other planets is only interesting to small minds. Of course there are trillions of other planets, why wouldn’t there be? Detecting them light-years away is done by finding tiny aberrations in the radiation from other stars indicating a transit. So what?

    Enrico Fermi said it best: “Where is everybody?” If there were other intelligent species who could make and use tools, in a universe 13.8 Billion years old, we would have been visited…

    • “Enrico Fermi said it best: “Where is everybody?” If there were other intelligent species who could make and use tools, in a universe 13.8 Billion years old, we would have been visited…”

      Perhaps we have been?

  18. Lots of guesswork and opinions at work. Right under our feet, the geologic partitioning of Earth’s crustal material to push lighter silicates to form continental cratons in Earth’s first 1.5 Gy is not understood or the early processes that started tectonics, other than maybe having a large Moon with its beneficial tidal flexing.

    Any conclusions about what other exoplanets might or might not be like are simply pseudoscience. Find one with a big Moon first. But just like any “answer” to the Drake equation, it’s all guesswork masquerading as science.

    Aliens Cause Global Warming
    By Michael Crichton

    an excerpt:
    “This serious-looking equation gave SETI a serious footing as a legitimate intellectual inquiry. The problem, of course, is that none of the terms can be known, and most cannot even be estimated. The only way to work the equation is to fill in with guesses. And guesses—just so we’re clear—are merely expressions of prejudice. Nor can there be “informed guesses.” If you need to state how many planets with life choose to communicate, there is simply no way to make an informed guess. It’s simply prejudice.
    As a result, the Drake equation can have any value from “billions and billions” to zero. An expression that can mean anything means nothing. Speaking precisely, the Drake equation is literally meaningless, and has nothing to do with science. I take the hard view that science involves the creation of testable hypotheses. The Drake equation cannot be tested and therefore SETI is not science. SETI is unquestionably a religion. Faith is defined as the firm belief in something for which there is no proof. The belief that the Koran is the word of God is a matter of faith. The belief that God created the universe in seven days is a matter of faith. The belief that there are other life forms in the universe is a matter of faith. There is not a single shred of evidence for any other life forms, and in forty years of searching, none has been discovered. There is absolutely no evidentiary reason to maintain this belief. SETI is a religion.”

    https://stephenschneider.stanford.edu/Publications/PDF_Papers/Crichton2003.pdf

  19. The message is a bit messy, but they seem to say that a high oxygen level in the atmosphere is a secure sign of life, but there can also be life on a planet with a low level of atmospheric oxygen.

    Therefore we should look for other signs.

    I would non belive claims of life in a planet with low a low level of atmospheric oxygen .

    /Jan

    • One might say, Jan, that atmospheric oxygen (O2) is a sufficient but not a necessary indication of life on a planet. Anaerobic life is possible (though it will require nitrate or sulfate, or some terminal electron acceptor).

      When one is looking from a few light-years away, though, one is restricted to what evidence one can observe. In this case, atmospheric O2.

      • A Chlorophyll-like signature in the blue-green spectrum in the light of a yellow sun would also qualify.

    • Should look less than 1% [less 10,000 ppm} CO2, but if below .5%, it’s definitely, life

  20. Salute!

    Hmmmm, so we’re the only “intelligent” critters in the whole wide world/universe that is capable of pondering its own existence? And we haven’t been visited? Remember the Prime Directive:

    “The Prime Directive (also known as “Starfleet General Order 1”, “General Order 1”, and the “non-interference directive”) is a guiding principle of Starfleet, prohibiting its members from interfering with the internal and natural development of alien civilizations.”

    I am not taking anything away from Fermi. He did much to further real science in a practical sense and not just produce math equations as Einstein and some others have like Hawking. Fermi and others in his crowd back then developed a means to offer us a source of power that could keep us going until we finally crack one of the codes that the “elders” did a dozen billion years ago. But if the universe that we know of is almost 14 billion years old, and the distances are so great it is difficult to fathom, then all of the sentient beings could just be so far apart that we haven’t made contact yet. And then, of course, there’s the Prime Directive.

    From one of the small minds that dream and strive to actually go out and beyond,

    Gums sends…

    • Gum-mybear,

      You attempt to use science fiction to argue a scientific point? The Earth and Solar System are apparently five Billion years old. The Universe appears to be 13.8 Billion years old, give or take. So, in 8.8 Billion years no one has developed space travel? How advanced will out technology be in the next ten years, or fify, or five hundred?

      When nuclear fusion can be controlled, star travel will commence immediately. When accelerating to near-light speeds becomes possible for a craft, the crew will experience the Fitzgerald-Lorenz time contraction effect, so some of the trips to nearby stars will appear to be brief journeys to them. Interstellar hydrogen is the most likely fuel source for long voyages.

  21. Emergence of life on a fully covered water planet is very unlikely, because the requisite chemicals will be too dilute for any chemical biogenesis. K. E. van Holde showed that long ago.

    It’s possible that such a planet could get seeded with exo-bacteria riding on meteors. Earth has Mars rocks that were ejected by meteoric impact. Large impacts on Earth, such as Canada’s 2 Ga Sudbury Basin, may well have sent Earth bacteria on an interstellar ride.

    On the other hand, I’d like to know how the atmosphere of a planet can become oxygen-rich without photosynthetic life. Early atmospheres are chemically reducing — CO2 (mainly), nitrogen, possible hydrocarbons, maybe hydrogen gas. No molecular oxygen.

    Certainly, primordial and exposed ferrous iron would remove any traces of molecular oxygen that might be on a new planet.

    Earth’s atmosphere is very far from chemical equilibrium. Any planetary atmosphere far from chemical equilibrium is prima facie evidence of living interference and manipulation. Ours has been interfered with and manipulated by photosynthetic bacteria and plants.

    In their absence, it would take space aliens to move an entire atmosphere into a chemically unstable thermodynamic state.

    So, an oxygen-rich atmosphere, all by itself, is enough to indicate planetary life. Once detected, the only question remaining would be whether the living source is endogenous or exogenous.

    Ockham’s Razor would plump for the former.

    But you never know. In a 100 kiloyears or so, we ourselves may be doing the modification of exo-planetary atmospheres.

    One can hope, and actively work for that future.

    • Minute amounts of molecular Oxygen are detected in Mars atmosphere. EUV/UV photo dissociation of abundant perchlorate ion ClO4- (carried aloft on dust particles) to Chlorite ClO3 to ClO2 to ClO is the likely reaction path. In Mars first billion years, the oxygen was likely combined with 2H that represented Mars now lost water. Which was also likely lost to photodissociation, with the light H escaping to space, swept away by solar wind ablation of Mars’ upper atmosphere. The ever brinier Martian surface water under such an evaporation would eventually leave behind the oxygen to combine with the chloride ion to make the perchlorate and with iron to make Mars red that we see everywhere in Mars soil. Somewhere under that many meters of wind deposited dust and soil should also be very thick layers of salt deposits from ancient now-evaporated oceans.

  22. Hello, Pat Frank. Wants to have a quarrel about Darwinian Evolution, does yer? Okey Doke.

    The core of the theory of speciation is that it will occur over millions of years, because it is a continuous process, like soil erosion. But it can’t be. Speciation must occur abruptly within brief periods of time, which makes it prohibitively impossible.

    Recall that two animals (a male and a female) are considered to be of the same species if they can mate and produce fertile offspring. Horses and donkeys are not of the same species because their progeny, mules, are sterile. On the other hand, a toy poodle and a great Dane are of the same species because they can produce little puppies than will grow up and produce more puppies.

    Now then, consider the first ostrich. On the day that the first ostrich was hatched from its egg, there were no other ostriches on the planet Earth. The first ostrich cannot mate with animals like its parents because they are of a different species. The first ostrich is alone in the world and, unless it finds another ostrich of the opposite sex during the brief span of its mating life, ostriches will not emerge as a species. But, we are told, the genetic traits that produced the first ostrich were the result of a random and extremely rare (as there is now only one ostrich) genetic mutation. So now, in the next decade (or whatever the lifespan of an ostrich is), the same genetic mutation must occur, except this time of a different sex, and it must occur in close proximity to the first ostrich, so that they can meet and mate. Well, that’s just impossible.

    Incidentally, I have studied Darwin’s Origin of the Species in a university classroom and no, I don’t think the Book of Genesis is literally true. I am a believer in intelligent design, although I do not have any defensible theories about the nature of the designer.

    Somebody designed ostriches and then caused them to be born. They didn’t just evolve from protozoa.

    • Your first paragraph is wrong, Ian.

      Mutation in HOX genes can drive speciation in jumps. Also here.

      Most of natural selection occurs in the uterus (or in the egg). A favorable HOX gene mutation can produce a new species in a single generation.

      Animals can mate across species. See the Liger. Your new ostrich can mate with the prior species. If its new gene is dominant, its offspring will be ostriches.

      I’ve published on so-called intelligent design theory. It’s rationally indefensible.

    • Ian Coleman

      “I don’t think the Book of Genesis is literally true”

      Why do you get a pass on deciding the Book of Genesis is not literally true? Just because your understanding has not be enlightened.

      With this kind of thinking, you’d be hard-pressed to believe, even if one of your loved one’s, that have already passed, were to come back and tell you otherwise. Luke 16:31

      Looking for life on other planets (or rocks) is empty.

  23. NASA should look for other Earth-like planets. Why would someone complain about this? Isn’t this form of discovery part of NASA’s job?

    You see how the Human-caused climate change hoax has poisoned science? NASA is involved in climate change research which causes otherwise rational people to dismiss everything else NASA does, even things not related to climate change.

    CAGW has poisoned the whole science atmosphere.

  24. The real problem I have with the “discovery of habitable planets” is that they all seem to be around unstable red dwarfs which spew fonts of radiation deadly to all known forms of life onto tidally locked planets with the narrowest of habitable zones (in as far as our own life needs are concerned). Call me when you find a rocky planet with water and oxygen orbiting a sun-like star in the habitable zone.

  25. There is Zero chance Earth exists by chance. There is Zero chance another Earth exists. There is no reason for life to exist, elsewhere. Few even understand why we exist.

    Man and his folly; looking for life, elsewhere.

    • It’s a pretty big universe, Cliff. It’s probably not a good idea to go ruling things out as impossible at this stage of human understanding.

  26. Hello, Pat Frank. Most of natural selection occurs in the egg? How can selection pressures influence eggs, or even zygotes? I was taught that environmental factors drive evolution by favouring some phenotypes over others. The reason that there are tigers is because there are certain evolutionary advantages to being a large striped beast with fangs and claws. None of these traits present advantages that are in any way apparent in the egg. (Which is the female gamete, incidentally. Sperm don’t have anything to do with evolutionary selection? Is that your theory?)

    Ligers are sterile. Strictly speaking, they aren’t a separate, naturally occurring species, even if their parents are. Lions and tigers are separate species, but if ligers were fertile, lions and tigers would by definition be of the same species.

    Most scientists reject intelligent design out of hand, because Science rejects supernatural causes. Of course, if you believe in supernatural forces, even if you can’t describe them reliably, you’re allowed to insert God into the mix. Which is what I do, although I emphasize that, to me, “God” is just a vague term that has no discretely defined meaning.

    Y’know, Pat, at some point in the history of the Earth, inanimate chemicals must have combined to form animate organisms. This must have happened on a wide scale all over the globe. Why don’t we see this phenomenon today? Did it just stop as abruptly as it started? What I’m getting at here is that there are huge gaps in our knowledge, and I just fill ’em with God. The concept of God is like putty for cracks in theories. Hey, works for me.

    • Ian, you asked, “How can selection pressures influence eggs, or even zygotes?

      The egg and the uterus are complex and dynamic environments, Ian. That environment interacts wit, and responds to, the developing offspring, which responds in turn.

      Genes in the developing organism turn on and turn off, and must do so in proper sequence, in part in response to environmental queues. If the turn on is too early or the turn off too late, the impact can be large.

      Feedbacks upon feedbacks. An incorrect developmental environment can impact the developing conceptus. Most likely for the worse, possibly to the advantage of the emergent young.

      Ligers are not sterile.

      but if ligers were fertile, lions and tigers would by definition be of the same species.

      Not correct. Lot’s of related species can interbreed. They don’t typically because their breeding habits differ, not because their gametes are incompatible.

      I coauthored a book chapter on chiral take-over and chemical biogenesis, Ian, On One Hand But Not The Other: The Challenge of the Origin and Survival of Homochirality in Prebiotic Chemistry.

      It needed to happen only once. Once a self-contained reproducing system emerged, it would take over.

      Earth is now a very, very different place than it was 4 billion years ago. More of the surface was ocean than now. Continents were small granite plates. Tectonics was intense with extensive and hyper-vigorous chemical smokers. The atmosphere was 60 bars of CO2, and large reefs of ferrous iron were abundant.

      None of that is present on today’s Earth. There’s no reason to expect similar observables.

  27. Okay, Pat, you’ve got me there when you point out that the Earth’s environment is dramatically different from what it was when life first arose.

    Or course, my doubts about Evolution are originally intuitive. It just doesn’t seem possible, for example, that the process that has produced animal intelligence is itself unintelligent, which is why I must believe in an intelligent designer. The universe is not a giant self-winding watch that just happened to produce my cousin Dave, who could eat live worms. I can no more believe that hummingbirds and bullfrogs and Shetland ponies are the result of random collisions of atoms than I can believe that St. Paul’s cathedral is a natural rock formation.

    A lot of times you run into people who are aggressively, angrily atheist. (Richard Dawkins and Sam Harris are prime examples of these gentry.) Obviously the strongest argument for the existence of God is that the world exists: Somebody must have made it, surely. The Theory of Evolution gives atheists a trapdoor through which they can slip to avoid the otherwise obvious proposition that the World was created.

    • Ian what gain is there in saying that a hard-to-understand system can be explained by supposing an impossible-to-understand system?

      That’s what you’re doing. God has no observables. It’s an empty set. There’s nothing to believe but invention.

      You’re right, there are angry atheists. Mostly they are angry about the long bloody history of religious people killing heretics; a history passed over in silence or with appeals for nuance by most religious people, and denied outright by the practitioners of religions that have not gone through the Enlightenment and who regret none of it, most notably those of Islam.

      But angry atheists, no matter how personally objectionable, do not lend substance to an empty set nor justify belief in it.

      Thanks for being civil, Ian. It’s appreciated.

  28. No one is asking anyone to prove a negative. Prove a positive. Prove that life elsewhere exists and has the ability to travel in space.

  29. Without the ability to travel to our closest star, I see little point in searching for basic life in the Universe. If we find ambiguous signs, it isn’t like we can send a mission there and find out. We will just end up with endless debates posited a endless hypotheses that no one can ever prove (but they might disprove some). The closest stars (less than 10 light years away) will require 100 years to reach and return, and there are not so many of those. The chances of finding life go up exponentiation once you go further out, but so does the amount of time to go there and establish any contact long past the point of being practical.

    Looking for signs of intelligence is more useful as it at least has the potential to be unambiguous and informative in a singe lifetime. It will likely have to be performed by machines that self-repair – not exactly send human ambassadors to establish first-contact. It will not happen in my live time, not in the lifetimes of many generations after me. (unless there is a big breakthrough in physics – so let;s put our energy in hard physics and dump all the soft-science crap like climate science).

    Until we master the ability to go there and look within a single lifetime, the game is pointless – although probably addictive to those that play it. The odds that we will find intelligent life forms (technologically advanced) are dimming ever year and now approaching zero.

  30. The Drake equation is:

    N= R x f(plnets) x N(potential life supporting) x F(live) x F(intelligence) x F(Civilization transmit) x L (time transmitting)

    We are moving in the first four variables, but it is the last three that matter, Fi gets put out to be ONE because the only example we have is Earth. (why not include Mars, Venus, and the Moon, except that that knocks down the odds)

    It is all guess work, and until we actually intercept a radio signal or have a verifiable visit, it will remain the stuff of SF.

  31. Actually Pat, your civility to me is downright heroic. Let me tell you, you go around telling educated people that you don’t accept Evolution, and the first thing they do is seat you in the Stupid section.

    Yeah I know, religion is mostly nonsense, and stupid nonsense at that. My tendency to just bring up questions of God is mostly mischief. I like to annoy people for fun. Not a nice thing to do, I know.

    I do suspect that people, like Richard Dawkins, who are essentially proselytizers of Evolution really do understand the arguments from the other side. Evolutionists have a lot of little cheats going on to counter reasonable arguments to it. The first, and dirtiest, is they tell you that you’re too stupid to understand the theory, because you’re the kind of simpleton who believes the story of Noah’s Ark. You have to get them on that one right away. And when you say, the world is far too complex to have arisen by chance, they say, it took billions of years, and in that time many things are possible. Well no. Species evolve in real time, and are delimited by time. There is no gradual way to make an ostrich. An animal is either an ostrich or it isn’t, and the genesis of the first ostrich had to happen during the gestation period of an ostrich. There ain’t no million years about it.

    I have never understood the logic of the proposition that Evolution is critical to the study of Biology. Come on. You don’t have to accept Evolution to understand how kidneys work, or trees grow, or how birds migrate.

    Anyway, It was good of you to respond to my posts, Pat. Not everybody is willing to argue and be patient about it.

  32. A surprising finding by the team is that the detectability index plummets for exoplanets not-too-different from Earth.

    What finding? It is only a hypothesis!!

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