What a planet needs to sustain life | Dave Brain

What a planet needs to sustain life | Dave Brain


I’m really glad to be here. I’m glad you’re here, because that would be a little weird. I’m glad we’re all here. And by “here,” I don’t mean here. Or here. But here. I mean Earth. And by “we,” I don’t mean
those of us in this auditorium, but life, all life on Earth — (Laughter) from complex to single-celled, from mold to mushrooms to flying bears. (Laughter) The interesting thing is, Earth is the only place
we know of that has life — 8.7 million species. We’ve looked other places, maybe not as hard
as we should or we could, but we’ve looked and haven’t found any; Earth is the only place
we know of with life. Is Earth special? This is a question I’ve wanted
to know the answer to since I was a small child, and I suspect 80 percent
of this auditorium has thought the same thing
and also wanted to know the answer. To understand whether
there are any planets — out there in our solar system or beyond — that can support life, the first step is to understand
what life here requires. It turns out, of all of those
8.7 million species, life only needs three things. On one side, all life
on Earth needs energy. Complex life like us derives
our energy from the sun, but life deep underground
can get its energy from things like chemical reactions. There are a number
of different energy sources available on all planets. On the other side, all life needs food or nourishment. And this seems like a tall order,
especially if you want a succulent tomato. (Laughter) However, all life on Earth
derives its nourishment from only six chemical elements, and these elements can be found
on any planetary body in our solar system. So that leaves the thing
in the middle as the tall pole, the thing that’s hardest to achieve. Not moose, but water. (Laughter) Although moose would be pretty cool. (Laughter) And not frozen water, and not water
in a gaseous state, but liquid water. This is what life needs
to survive, all life. And many solar system bodies
don’t have liquid water, and so we don’t look there. Other solar system bodies
might have abundant liquid water, even more than Earth, but it’s trapped beneath an icy shell, and so it’s hard to access,
it’s hard to get to, it’s hard to even find out
if there’s any life there. So that leaves a few bodies
that we should think about. So let’s make the problem
simpler for ourselves. Let’s think only about liquid water
on the surface of a planet. There are only three bodies
to think about in our solar system, with regard to liquid water
on the surface of a planet, and in order of distance from the sun,
it’s: Venus, Earth and Mars. You want to have an atmosphere
for water to be liquid. You have to be very careful
with that atmosphere. You can’t have too much atmosphere,
too thick or too warm an atmosphere, because then you end up
too hot like Venus, and you can’t have liquid water. But if you have too little atmosphere
and it’s too thin and too cold, you end up like Mars, too cold. So Venus is too hot, Mars is too cold, and Earth is just right. You can look at these images behind me
and you can see automatically where life can survive
in our solar system. It’s a Goldilocks-type problem, and it’s so simple
that a child could understand it. However, I’d like to remind you of two things from the Goldilocks story
that we may not think about so often but that I think are really relevant here. Number one: if Mama Bear’s bowl is too cold when Goldilocks walks into the room, does that mean it’s always been too cold? Or could it have been just right
at some other time? When Goldilocks walks into the room
determines the answer that we get in the story. And the same is true with planets. They’re not static things. They change. They vary. They evolve. And atmospheres do the same. So let me give you an example. Here’s one of my favorite
pictures of Mars. It’s not the highest resolution image,
it’s not the sexiest image, it’s not the most recent image, but it’s an image that shows riverbeds
cut into the surface of the planet; riverbeds carved by flowing, liquid water; riverbeds that take hundreds or thousands
or tens of thousands of years to form. This can’t happen on Mars today. The atmosphere of Mars today
is too thin and too cold for water to be stable as a liquid. This one image tells you
that the atmosphere of Mars changed, and it changed in big ways. And it changed from a state
that we would define as habitable, because the three requirements
for life were present long ago. Where did that atmosphere go that allowed water
to be liquid at the surface? Well, one idea is it escaped
away to space. Atmospheric particles
got enough energy to break free from the gravity of the planet, escaping away to space, never to return. And this happens with all bodies
with atmospheres. Comets have tails that are incredibly visible reminders
of atmospheric escape. But Venus also has an atmosphere
that escapes with time, and Mars and Earth as well. It’s just a matter of degree
and a matter of scale. So we’d like to figure out
how much escaped over time so we can explain this transition. How do atmospheres
get their energy for escape? How do particles get
enough energy to escape? There are two ways, if we’re going
to reduce things a little bit. Number one, sunlight. Light emitted from the sun can be absorbed
by atmospheric particles and warm the particles. Yes, I’m dancing, but they — (Laughter) Oh my God, not even at my wedding. (Laughter) They get enough energy
to escape and break free from the gravity of the planet
just by warming. A second way they can get energy
is from the solar wind. These are particles, mass, material,
spit out from the surface of the sun, and they go screaming
through the solar system at 400 kilometers per second, sometimes faster during solar storms, and they go hurtling
through interplanetary space towards planets and their atmospheres, and they may provide energy for atmospheric particles
to escape as well. This is something that I’m interested in, because it relates to habitability. I mentioned that there were two things
about the Goldilocks story that I wanted to bring to your attention
and remind you about, and the second one
is a little bit more subtle. If Papa Bear’s bowl is too hot, and Mama Bear’s bowl is too cold, shouldn’t Baby Bear’s bowl be even colder if we’re following the trend? This thing that you’ve accepted
your entire life, when you think about it a little bit more,
may not be so simple. And of course, distance of a planet
from the sun determines its temperature. This has to play into habitability. But maybe there are other things
we should be thinking about. Maybe it’s the bowls themselves that are also helping to determine
the outcome in the story, what is just right. I could talk to you about a lot
of different characteristics of these three planets that may influence habitability, but for selfish reasons related
to my own research and the fact that I’m standing up here
holding the clicker and you’re not — (Laughter) I would like to talk
for just a minute or two about magnetic fields. Earth has one; Venus and Mars do not. Magnetic fields are generated
in the deep interior of a planet by electrically conducting
churning fluid material that creates this big old magnetic field
that surrounds Earth. If you have a compass,
you know which way north is. Venus and Mars don’t have that. If you have a compass on Venus and Mars, congratulations, you’re lost. (Laughter) Does this influence habitability? Well, how might it? Many scientists think
that a magnetic field of a planet serves as a shield for the atmosphere, deflecting solar wind particles
around the planet in a bit of a force field-type effect having to do with electric charge
of those particles. I like to think of it instead
as a salad bar sneeze guard for planets. (Laughter) And yes, my colleagues
who watch this later will realize this is the first time in the history
of our community that the solar wind has been
equated with mucus. (Laughter) OK, so the effect, then, is that Earth
may have been protected for billions of years, because we’ve had a magnetic field. Atmosphere hasn’t been able to escape. Mars, on the other hand,
has been unprotected because of its lack of magnetic field, and over billions of years, maybe enough atmosphere
has been stripped away to account for a transition
from a habitable planet to the planet that we see today. Other scientists think
that magnetic fields may act more like the sails on a ship, enabling the planet to interact
with more energy from the solar wind than the planet would have been able
to interact with by itself. The sails may gather energy
from the solar wind. The magnetic field may gather
energy from the solar wind that allows even more
atmospheric escape to happen. It’s an idea that has to be tested, but the effect and how it works seems apparent. That’s because we know energy from the solar wind
is being deposited into our atmosphere here on Earth. That energy is conducted
along magnetic field lines down into the polar regions, resulting in incredibly beautiful aurora. If you’ve ever experienced them,
it’s magnificent. We know the energy is getting in. We’re trying to measure
how many particles are getting out and if the magnetic field
is influencing this in any way. So I’ve posed a problem for you here, but I don’t have a solution yet. We don’t have a solution. But we’re working on it.
How are we working on it? Well, we’ve sent spacecraft
to all three planets. Some of them are orbiting now, including the MAVEN spacecraft
which is currently orbiting Mars, which I’m involved with
and which is led here, out of the University of Colorado. It’s designed to measure
atmospheric escape. We have similar measurements
from Venus and Earth. Once we have all our measurements, we can combine all these together,
and we can understand how all three planets interact
with their space environment, with the surroundings. And we can decide whether magnetic fields
are important for habitability or not. Once we have that answer,
why should you care? I mean, I care deeply … And financially as well, but deeply. (Laughter) First of all, an answer to this question will teach us more
about these three planets, Venus, Earth and Mars, not only about how they interact
with their environment today, but how they were billions of years ago, whether they were habitable
long ago or not. It will teach us about atmospheres that surround us and that are close. But moreover, what we learn
from these planets can be applied to atmospheres everywhere, including planets that we’re now
observing around other stars. For example, the Kepler spacecraft, which is built and controlled
here in Boulder, has been observing
a postage stamp-sized region of the sky for a couple years now, and it’s found thousands of planets — in one postage stamp-sized
region of the sky that we don’t think is any different
from any other part of the sky. We’ve gone, in 20 years, from knowing of zero planets
outside of our solar system, to now having so many, that we don’t know
which ones to investigate first. Any lever will help. In fact, based on observations
that Kepler’s taken and other similar observations, we now believe that, of the 200 billion stars
in the Milky Way galaxy alone, on average, every star
has at least one planet. In addition to that, estimates suggest there are somewhere
between 40 billion and 100 billion of those planets
that we would define as habitable in just our galaxy. We have the observations of those planets, but we just don’t know
which ones are habitable yet. It’s a little bit like
being trapped on a red spot — (Laughter) on a stage and knowing that there are
other worlds out there and desperately wanting to know
more about them, wanting to interrogate them and find out
if maybe just one or two of them are a little bit like you. You can’t do that.
You can’t go there, not yet. And so you have to use the tools
that you’ve developed around you for Venus, Earth and Mars, and you have to apply them
to these other situations, and hope that you’re making
reasonable inferences from the data, and that you’re going to be able
to determine the best candidates for habitable planets,
and those that are not. In the end, and for now, at least, this is our red spot, right here. This is the only planet
that we know of that’s habitable, although very soon we may
come to know of more. But for now, this is
the only habitable planet, and this is our red spot. I’m really glad we’re here. Thanks. (Applause)

100 thoughts on “What a planet needs to sustain life | Dave Brain

  1. To use Mr Brain's analogy, if mama bears porridge was once hot, is there a chance that daddy bears porridge may one day be just right. Baby bears porridge may be too hot by that time and so then it would only be logical to then switch.

  2. This is pretty simplistic thinking. If fact, the worldwide scientific community has come up with a list of over 100 + specific planetary conditions that must all exist together it order to support life. The chances of all 100+ conditions aligning diminishes the likelihood of life by an infinitesimally small fraction of the number of planets theorized to exist in the universe. In fact, it may even lower the possibility to a crap shoot so low that its not unreasonable to being to think "life", like ours, is a very rare mathematical coincidence that may not be repeating anywhere but here, and for only a short time in the universe.

  3. What a load of BS. This guy needs to do his homework.

    Reducing life's needs to only 3 factors is either intellectually dishonest or ignorant.
    The requirements for a planet to sustain life hinges on more than 200 factors. Of the estimated octillion planets in the known universe, only several thousand planets are candidates for supporting life according to ONLY 50 of the known 200 factors. Adding the extra 150 necessary factors and the number of planets mathematically capable of sustaining life is 0 (Excluding earth).

    I'll grant that the math used is only accounting for the generous estimation of the known universe. If the universe happens to be much, much, larger than scientist estimate, only then will the chances increase beyond 0.
    But you're bucking up against contemporary science when you say that the universe is larger than scientist think because the scale of the universe is estimated based on strict rules and calculations.

  4. Some elements and substitutes should be mass produced and a better chance that sun constructions should be organised and implemented by studying its long term and short term uses

  5. He means complex life. Many microbes, and bacteria can survive everything from being adrift in the vacuum of space, or in active volcanos. It is plausible to suppose that some forms of them are spread all over space on simple levels. More complex life has more needs but remember, we only know about carbon based lifeforms, and all our examination is based on that. For all we know there are lifeforms based on other elemental building blocks entirely. In order to have the type of complex life we see here we need these conditions. That's all.

  6. Any one noticed the two in the front row 0:40 – Dead stare while the other looks over as if to say " What are they laughing at?"    LOL

  7. Actually, 1.5 million catalogued species. The 8.7 number is purely mathematics, and if those species existed, they are not known or catalogued.

  8. The energy is not getting in so much as more energy is being reflected out. Hence the Arora is brighter closer to the planet the cores power is reflecting it out! Seem very clear! The EMP from the solar flares are being pushed back from our magnetic cores charges

  9. These are the things that are required to sustain life. (Energy, nourishment, and water.) What are the requirements for life to come into existence?

  10. Breath your first action from evolved reactions to sun shine.
    Death is the subtraction of lifes perception of time.
    Cosmic retraction will collapse in when the last black holes combine.
    Outside the edge outside the faction vaccume blackness is what youll find.
    Its true ill gain traction thru theoretical rappen with evey line.
    Good news this already happened so just tap in to your immortal mind.
    Its the same bang again each universe.
    Same trajectory is how you get this earth.
    No change same thing same birth same hurse.
    Same pain same name my king is m.y.r.t.h.

  11. Those of us who actually "Think" realize that what it takes for a planet to host intelligent life is the free exchange of ideas in all areas of endeavor. The fact that not just youtube, but most social services including Facebook, Twitter, Amazon, Shopify and many others are actively censoring content that conflicts with their collective ideological world view, is dangerous and must be stopped. To that end we have been holding discussions with members of the House and Senate and have proposed a scenario in which these offending social and financial networks (including Amazon, Ebay, paypal and the like) can, justifiably, be nationalized by Executive Branch decree under the authority of the National Defense Authorization Act and operated as public utilities for the public good.

  12. You talk about the atmosphere on our planet and the temperatures on other planets that are bad now. You do not have the slightest idea what temperature would be on Mars if it had atmosphere, and it possessed, and why do not you know? because you did not think about what temperature and conditions would be in us if we did not have atmosphere, if it happened, we would have another planet similar to Mars.

    If the earth lost its atmosphere, and it was supposed to lose like others, taking into account the temperature of the cosmos and the heat of the sun, nothing would survive on earth.

    This ignorance only shows the state of your knowledge. The element that is water has no more influence. The assumption that water is one of the main building blocks of life is also based on the state of the earth because there is no reference.

    Indeed water is important but only for beings similarly built physically to us.

    That was the case with other planets next to us, they had life and atmosphere, and I have no intention of explaining what happened that they lost their atmosphere because that's a long topic. From which there are many other topics to understand the crux of why.

    I will explain what is happening that we still have it, in fact polar aurora depict our shield which was founded to protect us through the civilization which died out before us, it was such a gesture that looking at the land we are wasting

    If I would like to lead a lecture on how it looks from the very beginning, I suppose that the seminar would last a week. I'm happy

    You look like you do not know what you're talking about, and I think that's what it's all about, is not it?

  13. What humans need to do to sustain life: https://www.youtube.com/watch?v=CrX9rM0tulU&index=2&list=PLfvQ6khVmhPK_XM_IfcE2qKoHNvMMJJFM

  14. A question! If there is a discharge system in Mars why then there is no life?
    Moving of material in subsurface makes the magentic field, the absence of this move could remove this field?

  15. BUT WHAT IS LIFE? WHAT IS THE DEFINITION OF LIFE? NOBODY TELLS THAT, EVENTHOUGH IT IS THE MOST IMPORTANT THING, i.e. TO DEFINE SOMETHING BEFORE YOU START TO SEARCH FOR IT.

  16. It is really nice, that you have defined what life needs to exist, those 3 criteria – energy, nourishment, water. Great! Now define what LIFE actually IS, so we know what we are actually looking for. I hope you don't think that there is just "biological" life outhere?!
    There some few interesting lines from wiki:
    The definition of life has long been a challenge for scientists and philosophers, with many varied definitions put forward. This is partially because life is a process, not a substance. Philosophical definitions of life have also been put forward, with similar difficulties on how to distinguish living things from the non-living.

    Biology
    The characteristics of life

    Since there is no unequivocal definition of life, most current definitions in biology are descriptive. Life is considered a characteristic of something that preserves, furthers or reinforces its existence in the given environment. This characteristic exhibits all or most of the following traits:
    Homeostasis: regulation of the internal environment to maintain a constant state; for example, sweating to reduce temperature
    Organization: being structurally composed of one or more cells – the basic units of life
    Metabolism: transformation of energy by converting chemicals and energy into cellular components (anabolism) and decomposing organic matter (catabolism). Living things require energy to maintain internal organization (homeostasis) and to produce the other phenomena associated with life.
    Growth: maintenance of a higher rate of anabolism than catabolism. A growing organism increases in size in all of its parts, rather than simply accumulating matter.
    Adaptation: the ability to change over time in response to the environment. This ability is fundamental to the process of evolution and is determined by the organism's heredity, diet, and external factors.
    Response to stimuli: a response can take many forms, from the contraction of a unicellular organism to external chemicals, to complex reactions involving all the senses of multicellular organisms. A response is often expressed by motion; for example, the leaves of a plant turning toward the sun (phototropism), and chemotaxis.
    Reproduction: the ability to produce new individual organisms, either asexually from a single parent organism or sexually from two parent organisms.

    Alternative definitions
    Entropy and life

    From a physics perspective, living beings are thermodynamic systems with an organized molecular structure that can reproduce itself and evolve as survival dictates.Thermodynamically, life has been described as an open system which makes use of gradients in its surroundings to create imperfect copies of itself.Hence, life is a self-sustained chemical system capable of undergoing Darwinian evolution. A major strength of this definition is that it distinguishes life by the evolutionary process rather than its chemical composition.

    Others take a systemic viewpoint that does not necessarily depend on molecular chemistry. One systemic definition of life is that living things are self-organizing and autopoietic (self-producing). Variations of this definition include Stuart Kauffman's definition as an autonomous agent or a multi-agent system capable of reproducing itself or themselves, and of completing at least one thermodynamic work cycle.

    Biophysicists have commented that living things function on negative entropy. In other words, living processes can be viewed as a delay of the spontaneous diffusion or dispersion of the internal energy of biological molecules towards more potential microstates. In more detail, according to physicists such as John Bernal, Erwin Schrödinger, Eugene Wigner, and John Avery, life is a member of the class of phenomena that are open or continuous systems able to decrease their internal entropy at the expense of substances or free energy taken in from the environment and subsequently rejected in a degraded form.

    So tell me, does your search for signs or markers of extraterrestrial life also include all those general definitons of life (not just life as we know it)?
    I think that there is no point of inventing things like "habitable zone" – except habitable for some finite number of known earthly species, because Universe may be (and I am sure it is) much more habitable then we think. Maybe not necessairly habitable for us, but very well habitable for other forms of life that we have even ever dreamed of.

  17. There are WAAAAAAAAAAAAAAAAAAAAAAAAAAAAY more than 3 conditions necessary for life on earth. Extremely disingenuous video. Shame on you.

  18. To assume all life needs water…is pure stupidity. Life on earth evolved on a planet with water. Other life might thrive without water, & at far different temperatures than earth.

  19. 1 planet is habital and has a magnetosphere. 2 are not habitable and do not have magnetospheres. Going out on a limb and guessing a magnetosphere is kinda important.

  20. This presentation narrows down the necessary parameters for planetary life to an extreme degree. There are literally hundreds of parameters currently identified, all of which are necessary simultaneously for a planet to be life-sustaining. If we give each one of them a super-inflated one-in-ten chance of occurring on a given planet… we are looking at probabilities so small that the negative odds vastly outweigh the number of estimated planets in our galaxy. From the data we currently possess, it appears that the existence of other life-sustaining planets is, if we are being honest, a mathematical improbability which is so vast that many are now suggesting that the term “impossibility” is in line with the science.

    While I enjoyed the presenters excitability, he is simply wrong to suggest that life sustaining planets are likely to be found throughout our galaxy.

  21. Our planet needs to be taken care of and money used to make it work properly before spending it on exploration to other worlds. Or this planet is not long for us or History.

  22. Great topic, but there is a shortage of logic to describe the premise for Life on Earth! The one critical item for Life on Earth, left out in the graphics and text, was our Moon! Earth and Moon are a binary system. Liquid water had to be imported, and not in drips and drops from an improbable plethora of comet impacts. His own lecture revealed the reason Mars is devoid of liquid water on its surface- it was lost to space. Moon acquisition would have blasted any latent water into space, unless that most propitious collision was with a planet of ice! Plate tectonics are critical to maintain a rotating iron core and the subsequent protective magnetic field generated by that condition. An impact with a massive body of ice, with a small iron core, would not completely destroy the proto-earth, but may have cracked it! The iron core of the ice-moon would have bounced off the Earth and into orbit, attracting the detritus of the collision and becoming our Moon. The impact also tilted Earth's axis. Life, or its building blocks, was imported with that ice moon, and the Earth became its experiment. Hunger is Dark Energy!

    Lonely, scorched planet
    captivates hunting, ice moon.
    Oceans arouse Earth!

  23. I gotta give it to the guy he was by far the best Ted talk speaker I've heard in a long long time maybe the best period his presence and showmanship was awesome

  24. "Are we special?" lol only to life is life "special" all the ego of the human race exposed in one statement.

  25. Baby bear bowl was just the right temperature because mama bear mixed papa bear' s porridge with her own for baby bear into a smaller bowl. It's not rocket science.

  26. Without the moon stabilizing our planet we would not have life. Without our location being in the Goldilocks zone we would not have life. Without Jupiter acting as the solar system's vacuum cleaner pulling meteoroids away from us so we don't get clobbered we would not have life. We need so much more than these three things mentioned in the video.

  27. This is a genuine question and not a criticism. When we speak about complex life or just life, isn’t he speaking about life as we define it? What about a possible life form, which requires nothing that earth life requires? Why not conceptualize a form of life so different from ours that we could not exist on the same planet? This has already happened with earth species when life has been found in places where it had been previously supposed that no life could exist. Overall, a good Ted talk – I just wish people would preface such talks with the caveat of ‘life as we currently understand it to be’ or some such words. Thank you for an interesting presentation.
    🌲🌝☘️

  28. As humans we don’t have enough time to find out if there is other life out there ? We are only a fraction on time In earth life so we will never find out and after humans have gone life will still be here in earth maybe just wild animals? ….. it’s not about are we alone it’s about time …. distance

  29. He didn't mention location, size and rotation of Earth. Actually there are 200 parameters (still increasing) needed to accomplish to have a another Earth.

  30. I as Mr. Ahmed Ibrahim Hassan haji Ali living in Somaliland government saying: we are lodged on Earth by no choice of us. It is very condusive, comfortable to sustain our life. It is crystal blue, manificient and beautiful. Let us we humans maintain it, and try not to corrupt it for there is no elsewhere to go at least in the near future.

  31. This is very short-sighted, but then, all "scientists" are. He is talking only about that proverbial "life-as-we-know-it" factor. What happens if there are OTHER forms of life that, with such narrow minds as this, our "brilliant scientists" cannot ( or is is "refuse to") conceive?

    There are worms and caterpillars that live in the arctic, at temperatures around – and well below – zero degrees Celsius. https://blogs.scientificamerican.com/lab-rat/arctic-creepy-crawlies-part-i-the-ice-worms/ Read both parts 1 and 2.

    How about creatures that inhabit ocean depths that would crush any terrestrial creature that had the misfortune to fall down there? https://www.independent.co.uk/news/science/new-species-fish-found-deepest-living-mariana-snailfish-ocean-blue-planet-mariana-trench-5-miles-a8086806.html
    Then there are bacteria that live in temperatures close to the boiling point of water http://www.bbc.com/earth/story/20160209-this-is-how-to-survive-if-you-spend-your-life-in-boilin-water
    We don't know what this thing we call "life" IS or from whence it originated, so is it not being extremely arrogant to dictate under what conditions it can and will manifest?

  32. One of the questions that he did not investigate was why the large amount of water that is found on this planet. It is not just moist but sopping wet and it came from "Nowhere".

  33. What if "Life" existing in other planet bodies is in a very different form to ours on Earth? We're human and we're searching for something like us out there, something confined by our own foundamental experiences. So what if they're not living on the same conditions as we are, but something beyond, unreachable and inexplicable to our terrestrial comprehension? Are we too rash in concluding that there's no other "habitable planets"? Just wondering 🙂

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