How do they know that life on other planets would need water??

Question

obviously this on our planet need water to survive.. but what if that is not the case with whatever lived there? how can you think that when our planet is so different than all the other ones? i am no space expert.. but i dont understand

Answer 1

we don't.

but if we look for life with similar chemistry to our own (i.e. water, carbon, oxygen), we have a much better chance of recognizing it if we find it.

space has nothing to do with it. this is nothing more than common sense apparently a scarce commodity nowadays: you have to start somewhere, and this is where we're starting.

Answer 2

Well, H20 may not be required for  certain forms of life but it helps a lot.  Water has a high specific heat which allows a more regular climate, which helps organisms survive.  Also water is a universal solvent and is crucial in many reactions.  Reactions that need to take place for life as we know it.  Water is also easy to transverse so simple life forms do not require much adaptations to move around in water.  Water is the very important to life, but some life forms that we don't know about could live without water.  It is just that with water life is much easier to thrive, and all life on Earth requires some form of water.

Answer 3

They don't necessarily mean that.  They are looking at it from the perspective that if they find a planet with water, then it might have the kind of life we're familiar with here on Earth.

Answer 4

We don't know, but we know this; every where we find water on Earth we find life.  All lifeforms as we know them use water in their chemistry.

We have theories about sulfur or methane based life forms, but those are just speculation and idle thoughts.  So far we haven't come up with a set of reactions that produce as much energy and at the the same temperatures for liquid water as those that are carbon based.  All carbon based lifeforms require water to live.

This is why we need to go to other worlds like Titan and see if there is any signs of life there.  We are searching Mars for water because with water comes life; so that means life was once possible on Mars.

We don't know if life is unique to the Earth or not, but so far to the best of our knowledge it is.  We need to find out if that is true.

Once people thought the Earth was the center of the Universe, but the more we learn the more we find that our planet is merely one of billions and is fairly typical.  So the chances of life appearing on other worlds is possible, unless there is something more to the question of what makes life than what we know.

Our extra-solar planetary discover techniques are extremely limited and we can only find planets that are larger than our own.  So finding an analog for Earth isn't possible at the moment.  The James Web Space Telescope is going to be the replacement for the Hubble Space Telescope and while it is capable of seeing in different spectrums than the Hubble and not the visual one we find out more information from other visual spectrums and this new telescope should be able to see even closer to the edge of the Galaxy.  However, to detect another planet it has to be on the exact plane as our planet and in just the right conditions.  This limits the number of planets we can find.

Titan is a cold moon of Saturn with oceans of mostly Methane.  The Huggiens probe wasn't set up to find life, but now we know there is an ocean on another word.  On Earth life got its first start in the oceans.  So if there is life on Titan (doubtful, it is too cold) then it would most likely be near the methane oceans.

Europa is a frozen moon of Jupiter and underneath its ice crust, maybe kilometers deep there could be a frozen ocean larger than all the bodies of water on earth.  If so then the heat of the planet's core may be enough to fuel life.  Life forms live deep on the bottom of the ocean around volcanic vents, so this is just one possibility; currently the most likely possibility.

We can only understand what we know and what we see.  For hundreds of years Europeans thought that swans were only white, then the black swan was discovered in Australia.  This opened up a set of new possibilities; could there be a red or yellow swan?  We haven't found any, but no longer are swans only white.  So we look at the conditions we know and understand to see if there is life.  We look for the indications that we know are signs of life.  We also search other places to see if there is something else.

Life has many requirements for it to start; the right temperature, the right conditions, a stable enough platform for it to develop in and just the right mix of chemicals.  We have found that the basic chemicals for life can be found on asteroids and comets, so if those asteroids and comets were the source for life's fundamental building blocks on earth then it could have happened somewhere else.  We won't know until we go there.  This is just one of the many missions of NASA.

Answer 5

It is chemistry.

All life is a process of growth and movement powered by chemical reactions. Cells form and grow and move because of chemical reactions that require water. There MAY be other chemistry that COULD be the driving force of growth and movement that we could classify as life. But nobody has been able to make up a theory that would say what chemicals would be needed and how it would all work. Heck, we can't even completely explain how life on Earth really works.

Answer 6

Well, they don't know for sure, but based on observation of our own planet, H2O and Oxygen are needed to sustain life, and they have found planets similar to our own, just none that supports life.

Answer 7

The point is that you can speculate whatever you like, even to creatures with acid for blood like in Alien movies.  However, science doesn’t work on speculation – its theories can only be based on what is actually possible within what we already know.  

All complex life forms are composed of cells that are mainly water.  We use water based fluids for transportation of everything around our bodies.  Complex chemistry goes on in our bodies based on water.  

The chemical reactions between carbon, oxygen and hydrogen, used in lifeforms, have unique properties that cannot be re-produced by other chemical combinations.  For instance, oxidation of carbon substances to produce heat and energy is a unique process, and there aren’t other chemical elements in the universe that we are not aware of.    

You can speculate about fairies at the bottom of your garden, but until there is a scientific basis for that to be true, it is simply fantasy.  

Great, of you want to be a science fiction writer, but no good if you want to be a scientist.

Answer 8

Water is considered a 'universal solvent' and such a solvent is required for simple pre-life chemistry to occur.  There have been attempts to find alternative solvents, and I believe they've actually identified some suitable alternatives, but nothing that works quite as well as water.

Sort of like how we assume life will be Carbon based, because of the way Carbon bonds with other atoms allow it to easily form complex molecules.  Others, like Silicone, can form complex molecules too, but not as readily as Carbon.