Habitability of alien worlds

[@Jam-jt7bm]

Another thing to consider is our sun is strangely not an active sun, so having a sun that is relatively calm can provide life. That’s probably one of the reason why life started so early on earth.

[@RyanRidden]

A more active Sun would certainly have made the Earth less habitable, but I suspect unless it were faced with a direct shot from a coronal mass ejection the Earth's magnetic field should keep the surface fairly safe. Although bigger stars don't live as long, one advantage is that their habitable zones are further out, which decreases the probability of a habitable planet being hit by coronal mass ejections.

[@scottdorfler2551]

Our Sun is a slow spinner compared to most. Less magnetic lines to get twisted and snap.

[@Geomaverick124]

I remember reading about the late heavy bombardment and what it did to the inner solar system...Earth was fortunate since it wound up with a moon...the other 3 planets were so lucky. Mercury and Mars were kind of scalped when hit which caused them to lose a ton of mass...Venus was hit so hard that it started to rotate the other direction and totally destroyed the crust so much so that it lead to this continual vulcanism and runaway greenhouse effect. The paper said that even after this mars was habitable up until about 500 million years ago. It would have been interesting if Venus, Earth, and Mars were habitable today...where most of Venus would have had rainforests and swamps up to the poles and mars would have mostly tundra landscapes reminiscent of the last ice age on earth.

[@kassistwisted]

It amuses me that, while the earth on the monitor behind you has North in the top position, the earth you use in your simulation is "upside-down". But you are Australian. So maybe that is the right way up from your perspective. =)

[@RyanRidden]

Simulations always turn things on their heads!

[@michaelhoffmann2891]

I fail to understand your point. It's the right way up! The way it should be! Aussie, Aussie, Aussie! Oy Oy Oy!

[@veralenora7368]

Larry Niven wrote that we'll screw up this planet until its almost unlivable, then fix it. The upside? We'll know how to terraform.

[@RyanRidden]

We certainly know how to make a greenhouse effect now, which would be handy for terraforming Mars.

[@mariegilbert3272]

Harvey really likes your videos Ryan. He finds them very interesting.

[@RyanRidden]

Glad to hear he's enjoying the videos! If Harvey has any requests I can try to cover them in the future.

[@uhorne]

If I'm not mistaken, Europa (the moon) could possibly contain simple life beneath the surface, due to the warmth of the core. Based on that, could it technically be possible to have a semi hollow planet, with enough core heat to allow livable conditions for both plants and more advanced lifeforms? A bit like the sci fi comic "valerian: world without stars"

[@RyanRidden]

Europa is my personal frontrunner for finding life in the Solar System! It has all the conditions we think are needed for life, so there could well be some strange fish swimming around those hidden oceans!

[@uhorne]

@@RyanRidden and if it's a bit more evolved, it'll probably be ugly, based on experience from our own ocean creatures. Lot of ugly fish in the depths where the sun can't reach :D

[@eybaza6018]

@@RyanRidden life here would have to rely on chemosynythesis, since no sunlight reaches into Europa's ocean layer.

[@remibaele2169]

Thank you for the great work you make on your channel. Also many thanks for your English diction, it is perfectly understandable for non native english speakers.

[@faqgougle7641]

If we're being technical I believe that a star going into it's red giant phase would knock any planets that were formerly in that stars Goldilocks zones right into the 'the floor is lava zone'.

[@michaelhoffmann2891]

And the walls. And the ceiling. And the stuff in the fridge. Oh, and you! 🤣

[@RyanRidden]

Great point! The Earth will start becoming uninhabitable in a billion years or so once the Sun starts to expand. Even though the Sun has 5 billion years left, the Earth doesn't!

[@michaelhoffmann2891]

@@RyanRidden The good news: that's plenty for at least 2 full cycles from Cambrian explosion through Permian extinction to our days - with some additional mega-extinction events thrown in along the way. So, unless we manage to utterly sterilise the planet (unlikely as we'll be dead before managing that) - and even then there'd be some extremophiles left somewhere - it will be able to get a couple of do-overs, sans homo sapiens.

[@francisspinoy8408]

You might add that the stuff collected during the sun formation, contained a high percentage of dense elements previously originated in supernovae. This is why the sun has a high metallicity. This is all why the Earth is very dense and also why it contains uranium, which decay helps the planet inner to keep hot. I suspect that exoplanets made of lighter elements, probably the majority of them, will not be so favourable as Earth for the apparition and durability of life.

[@raidermaxx2324]

"A planet needs an atmosphere to be habitable.." Europa: Hold my beer....

[@global_nomad.]

enjoying drifting back to see some of your earlier videos...

[@janboreczek3045]

It is worth pointing out that this -18 degrees Celsius estimate without any greenhouse effect is valid only whn it is assumed that the Earth's albedo is the same

[@caramelosdasuburbia]

The problem is that we are observing exo planets from the past. If we somehow figure it out how to get there, they might be a lot different than we expected. Interstellars travels must be a lot shorter than we can even imagine possible now...

[@kalsikherensk8440]

Any planet within 100 light years of us is being seen only 100 years in the past. I think that it would take a very significant and sudden event to rule any out if we could get clear images of them. I mean, they can't all have sudden volcanic supereruptions, asteroid strikes, larger-than-normal solar flares or whatnot. There are a lot of stars within 100 light years of us that could harbour habitable worlds.

[@pacotaco1246]

I dont think weve made many exoplanet observations that have a time delay of no more than 3,000 years

[@LordJemse]

I love this sort of stuff

[@Protorit]

Just play as machine Intelligence, +200% habitability. No need to worry about nutrients either.

[@michaelhoffmann2891]

It's all machines and intelligence until the Zerg rush starts!

[@shahidee8]

great as always

[@IceSpoon]

So let's say you have godlike powers: What would you do to Earth to make it even more habitable for our humans standards?

[@spookedtea]

i love your videos!

[@divyanisinha7019]

Someone told me that we have found 300 million planets in our galaxy with water on them. Is that true? If it is, how many years would we have to wait so we can be advanced enough to travel there?

[@RyanRidden]

That's not exactly true. From population statistics we can fairly confidently say that there are at least 2 planets per star, and since there are a few hundred billion stars in the galaxy, there will be many billions of planets. As for water, its pretty abundant on most planets a reasonable distance away from their host star. We currently only know of a handful of planets that have water in the atmosphere, however, most of those planets are big like Jupiter, so not places we could live. All of the worlds are many lightyears away from us, and with current technology it's unlikely that we could really examine any interesting exoplanets. Hopefully one day some physicists stumble on a way to travel great distances quickly allowing us to really explore all the incredible worlds in our galaxy!

[@alansnyder8448]

I'm interested in know if the planets around Trappist-1 could be considered habitable. They often say an active sun would strip away the atmosphere, but what about the oceans, wouldn't underwater life do just fine in such conditions?

[@RyanRidden]

Very good question! There are quite a few astronomers who have been looking into this. Last I saw I think habitability was unlikely, as planets that close to a M-dwarf star would likely loose any atmosphere and water in the first few hundred million years due to high solar activity. There are some pretty cool papers that look at how the atmosphere composition is expected to change over time, but they could be wrong. Hopefully JWST will give us a better idea of what the Trappist-1 worlds are like!

[@veralenora7368]

What do youi think of Fred Hoyle's idea of panspermia?

[@RyanRidden]

I think it's certainly an interesting idea, and probably something we have done. Each lander and probe that has left the Earth has carried with it little stowaways comprised of the toughest microbes. Some of these microbes can survive the conditions of space, but as for surviving on the places they might end up, I don't think anyone knows. This concern with contaminating other worlds through panspermia with Earth life is what lead to astronomers sending the Cassini spacecraft diving into Saturn on its last command. They did this so that there would be no chance of Cassini colliding with the moons Titan and Enceladus, where it seems possible that Earth life could find pleasant. If you want to find alien life you need to be very careful that you haven't just found the life you took with you!

[@ilijas3041]

What exactly means when u say "more habitable" than Earth? I always understood it as dichotomy, it either is or it isnt. But with my background in social science I guess there are many things I understood wrong within this topic

[@RyanRidden]

Habitability is better represented as a continuum from uninhabitable to the perfect world. In this case the perfect world is one where the conditions are maximized for life, which will have some differences from Earth. There are lots of different components that lead to habitability, for example a world with everything right, but has very little water. Such a planet would look something like Tantooine from Star Wars. Life can live on the world so we would say that it's habitable, but it's not the easiest, or most ideal place for life to call home, so not as habitable as the Earth.

[@QuantumAscension1]

Just to add to what Ryan said, the proper term is "Super-habitability". It refers to a set of environmental conditions that work in the existential favor of life, more-so than earth. Kepler 442b is a potential example. It's little larger than earth, with about 30% more gravity, and thus might have a thicker atmosphere, but not too thick. More importantly it orbits a K-class star which doesn't produce the dangerous solar flares of M-class stars and it will have a life-span 3-5 times longer than our g-class sun. so theoretically it could have tens of billions more years to sustain life, whereas Earth likely only has perhaps another billion years before it becomes too hot to support life on the surface (barring some artificial means of protection).

[@michaelhoffmann2891]

@@QuantumAscension1 I agree with you, though should point out that "perhaps another billion years" is twice from the Permian extinction to today (plus various other mass extinction events). There is some solace in that: no matter what we do and whether we leave this a planet as dead as at the beginning of the Cambrian, it could still start over with time to spare! Most likely, we'll leave it about as dead as at the KT event - and that took only 65 million years before us hairless apes created the mess we're in!

[@russellsharpe288]

Surely nutrients are recyclable?

[@RyanRidden]

They certainly are, but on large timescales they can get removed from the system and buried by erosion/sedimentation. If there are no processes that can pull up new nutrients, either through geology or biology, then eventually it would become scarce. A example is the phosphorus cycle. Phosphorus is needed for plant growth on forms, but it is often washed away, where eventually it will settle on the sea floor and become inaccessible to most life. Naturally it is replaced by volcanism and erosion of mountains raised by tectonic activity. So without a geologically active world, the phosphorus cycle would eventually fail, and with it life like the Earth's that requires phosphorus.

[@russellsharpe288]

@@RyanRidden A most satisfactory answer - indeed I wasn't thinking on long enough timescales. Thanks for taking the trouble. Nice channel btw.

[@Petter1900]

Wheres the alien ring-gate when you need it?

[@RyanRidden]

I'd settle for a mass effect relay!

[@SnootchieBootchies27]

But... we "happen" to be smack in the middle of the goldilocks zone. Maybe it's actually much smaller in reality than the projections of possible range. I.E. The reason we are here is simply because we are *here*

[@RyanRidden]

It's almost certain our concept of the Goldilocks zone and what is acceptable for habitability is wrong/incomplete. It's a concept that in many ways is restricted by our own prejudices of what life can be and tolerate. Over the last few decades as biologists and astrobiologists have explored extreme environments, each time we have been amazed by just how tenacious life is and expanding our view of what could be an acceptable Goldilocks zone for life. In the end it's all just educated guesswork until we can understand the origin of life and explore other worlds.

[@Ψευδάνωρ]

Thats the problem, you believe there is a reason of why we are here and there isn't, we just happen to be in a perfect spot with the perfect conditions at just the right period of time for life like ours to exist.

[@SnootchieBootchies27]

@@Ψευδάνωρ i think you misunderstood my comment. I was basically saying the same as you. We only exist because we're in the right time and space, not for any "special reason"

[@Ψευδάνωρ]

@@SnootchieBootchies27 ah ok we cool then

[@matthewtheobald1231]

This dude's jaw line is giga chad status

[@VexMage]

Out of curiosity is using sol-centric phrasing the official stance for science?

[@RyanRidden]

Good question! Since we know the Sun and solar system very well, they are useful measuring sticks to compare to other objects. There is no fundamental scientific reason behind this, rather it's just easier for us to conceptualize something by saying it's 2 times the mass of the Sun, instead of 4x10^30 kg.

[@VexMage]

@@RyanRidden That makes total sense for measurements! I mainly wonder about using the terms solar system and sun, for example. I always figured they were proper nouns for our star and star system but while saying sun insead of star comes easier to me using the term solar system seems off. Indeed a solar panel seems to me specific to our sun although intellectually I know such panel should work in relative approximation to a star in another star system. I'm sure this is all semantics, like making a Xerox or using a Keenix; and of course I'm not pedantic as I myself interchange them all the time. I main wonder if there's any specific formal usages for science literature. Also here's an overdue subscription

[@skg901]

Humanity: I am looking for a few more habitable world... Universe: Thou hath way too much expectation. Humanity: makes youtube videos...

[@RyanRidden]

Earth is good, but it can be better! That said a more habitable world than the Earth would probably be quite unpleasant to us.

[@skg901]

@@RyanRidden Yes... Its better to start on a barren world and terraform rather than start on a planet with lots of water and some indigenous life. Imagine dealing with a plethora of new viruses and bacteria, when one coronavirus brought us to our knees... Infact, if we start digging deeper into the biological aspects of the expanse, say Martian or Belter physiology and how it changed due to constant exposure to microgravity, we'll start appreciating our Earth even more.😅

[@skipperg4436]

@@skg901 ideal planet for colonization would be something like an Earth before life has appeared. The world with liquid water and atmosphere consisting of nitrogen, carbon dioxide, ammonia and or methane, but completely sterile. As for alien viruses/bacteria they would be harmless to us because our native viruses/bacteria co-evolved with us to be able to penetrate our bodies defenses. We are almost immune to viruses/bacteria that infect birds and fish. We can get POISONED by bacteria life cycle products though. Our bodies are hard to infect but easy to poison.

[@skg901]

@@skipperg4436 reminds me of alien covenant movie. Even without the Aliens its much more scary. The killer can be microscopic. We need some sort of AI based life spectroscopy which can stay in orbit and provide information about indigenous life on the planet especially the microspic ones, which cameras cannot see. We cannot sent probes down on the surface. It may affect the existing life and alter their course of evolution permanently. However, there may even be seasonal patterns which can be dangerous. Better to start with a barren world. Guilt free and Risk Free 😅.

[@Smoking_cat11]

I think mars size is what caus it to not be habitable

[@pyrolopez854]

A bet you anything the fanboys of star citizen gotta hate the NMS thumb nail lol

[@skipperg4436]

Hm, numbers don't match: root mean square velocity of carbon dioxide and nitrogen gas molecules is way, way below Mars escape velocity. So they should never leave planet's gravity well... Am I missing something?.. Heck, if only gravity is in play than Moon and Galilean moons of Jupiter should have an atmosphere as well... It's so sad really: our world could have been much better place if there were 2 more habitable planets around even if harsh...

[@Yora21]

K-stars are best stars!

[@RyanRidden]

They are definitely oK with me!

[@michaelhoffmann2891]

Yeah but everything always looks like it's Red Alert on the Enterprise! 🤣People wouldn't have the blues, they'd have the.... err, the purples! Or the greens!

[@michaelhoffmann2891]

Begins video talking about "only habitable planet brimming with life that we know about". Shows planet Earth with shot of Australia. Yeah, mate, but our life is trying to kill you dead! Also, keep in mind that the advantage of a moon is more love poetry, increasing the ... uhm, procreation rate of the poetic species! To a point at least (which we've definitely gone past).

[@RyanRidden]

No better way to increase biodiversity than an extreme biological arms race! I wonder if there is a way to study how/if the beauty of an environment affects the selection of intelligence. Definitely an interesting thought!

[@michaelhoffmann2891]

@@RyanRidden Beauty is in the ... err, visual acquisition apparatus on the tentacle stalks of the observing sapient entity! 🤓