Idk if to put biology or planetary science so ye.
In: Biology
Think of it like this: space is extremely hostile to biological lifeforms that have DNA:
– cosmic rays that pierce through DNA and cause mutations and decay (necrosis)
– solar radiation that could literally cook any DNA that’s exposed to sufficient quantities, causing cancer and other maladies
– exposure to vacuum prevents any respiratory functions
– nucleonic radiation from, say, a nearby gas giant or super nova, again causing necrosis
– plasma winds from nearby super nova that could strip the atmosphere and the top layer of soil across the entire planet
– extreme cold or heat that prevents any metabolic functions
The list goes on and on. Basically, the only reason we have a biosphere is because the Earth protects us from all those effects:
– our magnetosphere deflects cosmic rays
– our atmosphere diffuses the most harmful blue and UV radiation from our sun
– we have a breathable oxygenated atmosphere, mostly on account of our magnetosphere protecting it from being stripped by the sun
– our magnetosphere also protects us from nucleonic radiation
– there are no nearby super nova
– we are the right distance from the sun to not receive too much radiation, but enough to sustain photosynthesis
There’s a reason why every other planet in our solar system is sterile: they don’t meet any of those criteria. A bit of observation bias due to detection techniques, but nearly all the exoplanets we’ve detected are also likely sterile because either they’re orbiting a red dwarf closer than our moon orbits the Earth, or because they orbit some blue giant that would cook them at any distance.
So what we’re left with is a very narrow range of unlikely conditions:
– a strong magnetosphere
– high water content, but not enough to ensconce every landmass
– high metalicity, rich in things like calcium, phosphorous, and iron
– Goldilocks zone from a stable main sequence star
Find one of those, and you just might find aliens.
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