What is the criteria for there to be life on other planets?

Question

Why do astronomers, or people in general, believe that in order for a planet to sustain life, it must meet the criteria that sustains life here on Earth. Why can't there be other beings on other planets with the ability to inhabit a planet where it is 100 C and a carbon dioxide atmosphere--because that is what THEY need to survive, not what WE need. Are we such a self-centered species that we think in order for there to be life, it must be exactly what WE need, disregarding the possiblity of THEIR needs? What are you're thoughts on such criteria imposed on us by our fellow astronomers and general public?

Answer 1

We are looking for carbon bases life similar to here on earth because it is easier for us to analyze and understand the result. This doesn't mean that life on other planets have to be carbon based.

We are looking for planets similar to our for life since we know for a fact that life can evolve in planet like earth. But again this doesn't mean that life cannot evolve in a planet completely different from earth with such adverse conditions.

Answer 2

Scientists say that life as we know it could not exist on a planet that has conditions much different than those on earth. I agree with that.

Answer 3

Scientists are looking for anything like this, but they're not finding it.

Answer 4

Actually, the main criteria for life on other planets is water which is hydrogen and oxygen, and does not include food which is a by-product and oxygen which can be extracted, as everyone is led to believe or conclude.

If other elements are available that can combined to form all those products (meaning creating water, food or oxygen from existing source), it would be a bonus.  We now have the technology to combine existing resources with others that we have to bring in.

The only issue will be if it will be feasible to do so.  Remember that bringing the needed resources (just like oil from the middle east to other parts of the world that depend on it, like Japan, costs money) would weigh heavily on the decision on whatever criteria will be needed as of the moment.

I stated "for the moment", because it may change depending on the need and advancement in technology.  If the need is urgent, then it will be obvious that the cost won't matter.  However, if there are other options that cost less...

An example would be is that if the travel time to reach that planet and the weight of the load of the much needed resources (not to mention the risks involved) would be cost-beneficial to the point that immigrants and resources alike could be transported at a cost less than the risk of extinction on earth because of over population or global warming, (I think those will be the only plausible reasons why we need to "transfer" people on earth to other planets except only those people needed to study it), then we can rely on the good old science fiction movies creation in Hollywood about creating life on a planet other than earth.

However, in recent, as recent as the last two to three years, Time and Newsweek magazines have featured scientific concepts on artificial survival domes, similar to the Hollywood theme, that can sustain a population on a moon or planet with the intention of exploiting its natural resources.

I am surprised.  Because if survival is the main issue, then the same concept can be used to save the human race.

Think about it.  I am not normally righteous these things.

I hope that I have answered your question to your satisfaction.

Answer 5

Just theories, I pay them no attention. Man's ignorance far outweighs his knowledge.We won't know for sure until we actually go there.

Answer 6

life on earth follows certain biological criteria. as far as we know, all cells and carbon based organisms have these criteria. cells simply couldn't survive in 100C temperatures. there's just no way. we have examened all the life we have on earth, and came up with certain criteria for them. life can't survive on venus because everything would disinigrate. laws of biology don't change on location. there is a better chance of organisms surviving in cold weather than hot weather.

no we can't take all of the universe as evidence and come up with ALL criteria for carbon based life because we haven't examined all of them.

current criteria for life-

- air rich with carbon doxcide, or oxygen

- temperate climate

- water

- source of food

so those are my thoughts.

Answer 7

Because until recently everyone was taught and believed that life required the conditions we have here on earth.

Exobiologists are studying the potentials for life in all sorts of extreme conditions.  Scientists are changing their views.  The general public on the other hand will probably persist with the old notions.

Edit:  I should add, that we are looking for signs of life on a planet right now, one that is not like ours, it is called Mars.

Answer 8

Scientists are looking for conditions that could support ANY kind of life on other planets, not just those conditions that support human life.  Here on earth, all sorts of strange conditions support life.  For instance, there are bacteria than can survive extremely high temperatures (well above boiling), without sunlight, and can use sulfur-based compounds as their energy source.  These bacteria are found near hydrothermal vents in the ocean.

Scientists are looking for anything like this, but they're not finding it.

The only things that scientists are really looking for to indicate life might be present is the presence of water, some sort of atmosphere, some sort of reasonable temperature, and some sort of carbon-based molecules.  All life as we know it lives within certain paramters, all life requires water, and all life is carbon-based.  So, scientists do use those assumptions when searching for life because, currently, we have no reason to believe life could exist otherwise.

You really should learn more about this subject before you accuse scientists of not knowing what they're doing or being arrogant.

Answer 9

There is no criteria.  You are perfectly correct in assuming that life can exist in a lot more places than just on another earth.  Microbes existed on the unmanned Surveyor III camera for 3 years on the moon before it was brought back by the Apollo 12 astronauts. If life can exist in the vacuum of space, it can exist anywhere.

Answer 10

I used to ask this very same question, however I foud that the astrobiologists actually have very good reasons to limit the possibility of life to certain conditions. Life requires a few things:

1) Complex chemistry. This means that there must be some kind of chemistry available on the planet, moon, planetoid, whatever, that can make complex molecules of many different shapes -- this is because different shapes = different functions, and many biochemical functions are necessary for even the simplest life.

2) Energetic bonds. Life thrives on energy, it's why we eat or photosynthesize or parasitize on other organisms, etc. It's absolutely essential that whatever chemistry the life is based on has energetic bonds that can easily be broken to access that energy and stored in the organism.

These two requirements alone *severely* limit the capacity for life to develop in the universe. There are only a few known chemistries that could possibly sustain life:

a) carbon chemistry, such as our own. Carbon-based chemistry requires a lot of hydrogen and oxygen for energy, this is why liquid water isn't just convenient -- it's absolutely essential for carbon-based life. This among other reasons means that we would only expect to find carbon life on planets with liquid water and within temperature and pressure ranges where this is possible.

b) silicon based chemistry. Silicon has the same number of valence electrons as carbon and so is capable of likewise complex and energetic chemistry. However, silicon based life is less likely than carbon based life overall because it's much more frigid and its chemistry allows less energetic reactions. (It's telling that there is more silicon on earth than carbon, yet still carbon based life arose instead of silicon based life!)

c) Nitrogenous-phosphorous based life. I haven't read a whole lot about this possibility but I do understand the "habitable zone" for such organisms would be different than carbon based life.

d) Ammonia based life. Ammonia based life would utilize chemistry based on cyanide and other things poisonous to us, and they would be found on extremely cold and extremely high pressure places (such as under seas of ammonia or planets with thick atmospheres).

Etc.! Sorry to blab so much but the direct answer to your question is that what astrobiologists do is entirely reasonable -- life requires certain things to be physically possible, and those "certain things" are only possible with a narrow range of different possibilities. Each of those possibilities is different, yes, but they are still narrow.