Describe extraterrestrial life?

Question

If we do find extraterrestrial life wouldn't it be completely different from the lifeforms we are used to on Earth? For all we know extraterrestrial lifeforms probably breath toxic gas or something instead of oxygen or drink liquid mercury instead of water. The genome of extraterrestrial life forms is probably completely different from the organisms on Earth or perhaps they might not even use double stranded DNA or single stranded RNA as a blueprint. Maybe they have a hexagonal-like structure for their genetic blueprints or they might not even use genes. So when we do find extraterrestrial matter, how can we classify it as a life form or just a bunch of molecules bunched up together to make some sort of complex organised chemical elements?

Answer 1

Maybe not, maybe humanoid life is prevalent throughout the universe and maybe humanoids are such a successful form of life that opposable thumbs, two arms, two legs and one head is what evolution inevitably ends up with.

Answer 2

Non-existing.  There is not a shred of evidence that there is life anywhere except Earth.

Answer 3

You are quite correct. If there is extraterrestrial life, there is no guarantee that it would be anything like terrestrial life.

That said - there are good reasons to suppose that it would be water and carbon-based, like terrestrial life is. Carbon chemistry is the only way to acheive the complex variety of chemical reactions that are required for life (carbon compounds can be long-chain or shorter, they can be hydrophobic or hydrophilic, positive or negative, etc.). And they only acheive this complexity of chemistries when in an aqueous environment.

No other element does this: silicon comes closest, but even it is orders of magnitude less complex in its chemistry than carbon compounds.

There are a number of conditions which must be met before something can be described as "life": responsiveness, change, reproduction, growth, homeostasis and (cellular) organisation.

As it currently stands, anything not fitting all of these is not considered "alive" (which is why there is debate about whether viruses can be considered "life" or not).

So any extraterrestrial phenomenon not fitting the majority of these features would almost certainly not be considered alive.

Answer 4

i'd bet most would be just or alot like us, the animal kingdom would have species we never dreamed of of course. but the intelligent and technologically advanced intelligences would be very similar to us. i think life will almost always favor this design, it's just...life.