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this episode is brought to you by - Lane

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simplify your online life with a free

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account from - Lane not too hot not too

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cold just write the habitable zone or

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the region of space within a star's

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orbit that strikes that critical balance

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is often called the Goldilocks zone for

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just that reason we know that Earth

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resides within the sun's habitable zone

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otherwise we wouldn't be here wasting

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time on YouTube but what is it exactly

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that makes a planet habitable is it

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simply being the right distance from the

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parent star or are there other factors

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that play a role in determining where

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life might arise a new study titled

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habitable zone predictions and how to

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test them hopes to foster a more

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comprehensive approach in cataloguing

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exoplanets and trying to figure out

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where we're most likely to find life in

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the universe while we still have a lot

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to figure out regarding where life is

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likely to arise we do have some ideas

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that can help guide the search as of

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right now exoplanets are designated as

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potentially habitable if they orbit

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within their star's habitable zone

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meaning they're not so far away as to

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risk freezing nor are they too close to

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risk burning up the problem with

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determining habitability is that we make

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a lot of assumptions in the process we

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assume that there have to be large

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bodies of liquid water on the surface of

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the planet we assume that the planet has

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to be rocky that it has tectonic

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activity and that it has an atmosphere

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containing oxygen it's no mystery why we

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make these assumptions it's what we see

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on earth and each of those assumptions

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is based on the fact that we humans rely

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on these characteristics to survive but

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the things that work here on earth may

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not work on exoplanets throughout the

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universe

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for example there is some evidence to

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indicate that atmospheric oxygen does

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not automatically guarantee life and

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other data seems to show that the

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presence of oxygen early in a planets

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formation could actually prevent the

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genesis of basic life then there have

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been other studies suggesting that plate

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tectonics are not necessary or that

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water worlds may not support life after

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all so really we have evidence for and

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against all of our assumptions to make a

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long story short in order to more

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accurately assess the habitability of

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far-off worlds we'll need to rely

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heavily on the next gen Space Telescope

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slated for launch in the coming decade

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they'll be able to help us get a better

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look at atmospheric conditions on

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planets many light-years away and refine

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our understanding of the origins of life

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but in the meantime based on our current

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understanding where should we look for

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evidence of life beyond Earth for

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starters it's

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likely that small stars like red dwarfs

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are not bright or warm enough to support

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the development of life and that it

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might be uncommon that planets orbiting

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a red dwarf would have a stable

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atmosphere these are still hotly debated

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points but at least we can narrow down

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our search by eliminating smaller cooler

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stars from the running then we have

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larger hotter so-called type-a stars

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these include Sirius a altai year and

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Vega studies suggest that this type of

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star is too hot to allow for habitable

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planets if we cross Type A stars off the

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list of candidates that leaves

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unsurprisingly sun-like stars if we

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limit our search to star similar to our

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own in theory we should be on the right

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track to find at least simple life-forms

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beyond Earth but the star is only part

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of the equation we also need a planet

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with the right mix of characteristics as

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of right now there are two distinct

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types of planet that have promise the

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first is rocky planets like Earth or

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Mars with large bodies of liquid water

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the second is water worlds or planets

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that are entirely or almost entirely

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covered with water

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if Earth is any indication anywhere

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there's water there's life so it would

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make sense that we would find some form

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of life on planets orbiting sun-like

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stars within their habitable zone with

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plenty of surface water however there's

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a big problem with water worlds any

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planet with around 50% water by mass

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would likely have a thick layer of ice

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at its core mantle boundary which would

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likely prevent hydrothermal activity the

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heating of oceans by subsurface vents or

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other hydrothermal activity is crucial

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to an environment that could support

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life

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this activity is what makes Jupiter's

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moon Europa so enticing a subject for

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study it has massive subsurface oceans

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that are heated by geothermal vents

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which also provide essential compounds

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for life since Europa is fairly close by

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in cosmic terms it would make a prime

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for study for the viability of water

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worlds if we were to find life on Europa

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it would all but guarantee success on

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other similar watery planets in the

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meantime based on our current

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understanding of biological processes

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and their connection to planet formation

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the best places to look for life as we

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know it are rocky planets with sun-like

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stars of course if we expand our

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imagination to include forms of life

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that are very different from what we see

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on earth places like Saturn's moon Titan

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could be quite promising Titan is home

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to an environment that is almost perfect

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for the development of exotic life it's

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rich in prebiotics conditions and

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organic chemistry the only difference is

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in

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of liquid water Titan has lakes of

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liquid methane the question is is it

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water that leads to the development of

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life or is it simply the presence of a

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liquid solvent to serve as a breeding

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ground for simple compounds to answer

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that question we'll need to launch a

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mission to Titan if we found life there

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it would shatter the preconceptions we

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have about the necessary conditions for

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life and we'd need to completely

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re-evaluate our targets for study but

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until then we're stuck mostly guessing

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at where we might find extraterrestrial

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life forms in this humble youtubers

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opinion we should send missions to both

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Europa and Titan and probably Enceladus

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for good measure

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we have promising locations in our own

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neighborhood and it would be a waste not

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to study them more fully we should

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absolutely use the upcoming next-gen

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space telescopes to have a closer look

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at super distant exoplanets but when it

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comes to space closer is much easier the

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science of habitability is challenging

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but not everything has to be you can

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[Music]