Is it possible that there could be lifeforms somewhere that are silicon-based rather than carbon?
929096
The reason all life on Earth is carbon based is because of some of the unique qualities of the element, such as the way it binds to other elements (it's quite complicated to explain - just trust me on this point!)\n\nSilicone shares enough of these qualities to make it a viable alternative to carbon in terms of organic life. We're not sure why carbon ended up being the basis of life on Earth - it may be pure chance. However, if there is life on other planets, then (as far as we know) it would be based either on carbon or silicon.
896421
Hi\nYes there are. There has been microscopic animals found in mars.
857433
Yes, all life is based on carbon.  All living systems have carbon compounds in them.\n\nBecause carbon is unique among the elements in forming long complex chain molecules it is generally believed that any life we find in the universe will be carbon based.  This may not be true if electronic only forms of "life" are found.
1170146
There are traditionally only 4 elements - Fire, Water, Earth and Air / Wind. These were believed by the ancient greeks to be the fundemental basis of life. \n\nScientifically, there are not only several elements needed for life to exist but also certain conditions of environment also - the best elemental mix would struggle to form life in the near vacuum of space.\n\nAll known life is carbon based. The other elements needed (depending on environment) would include hydrogen, oxygen, and nitrogen.\n\nIf you are talking about throretical extra terrestrial life, this could be silicon based and have an entirely different chemistry to anything we would recognise.
757352
Certainly not.  There are tons of unicellular organisms like amoeba and other protozoa that are quite nicely alive, but don't have any form of sexual reproduction, so don't come from an egg.
1153140
Amongst those billions of planets out there the following preconditions suggest themselves as needing to be in place, which would rather whittle down the number of planets that can in fact sustain life:\n\na star that is not going to develop into a supernova or a black hole\na plentiful supply of water\na planet or moon large enough for its gravity to retain its atmosphere\nthat atmosphere to contain oxygen\nthe upper atmosphere able to screen out harmful radiation from the star (eg plentiful ozone)\nno extremes of temperature\nno excessive volcanic activity\nthe ingredients for the basic building blocks of organic chemistry exist in the planet's composition\n\nThere are only two elements that are serious candidates for forming the complex molecules needed to make proteins, amino acids and the other components of living cells: carbon and silicon. Fortunately Carbon is the sixth most abundant element in the Universe. The Earth is relatively well endowed with silicon but it was still carbon-based life-forms that developed here. The key step is the creation of organic chemical compounds and the existence on the planet of conditions under which they can form.
1186850
I believe there are, but they are far and few between. We'll refer to those one's as diamonds. The other more common species we'll refer to as coal, there's lots of that and it's only good for burning =)\n\nGood luck in your search.
828326
scientists believe there may be life on Mars because Mars have water in its atmosphere. It may only be a small amount, but could provide life to certain living organisms that need very little water
522340
As of right now, 0, the "clones" they have are not exact carbon copies, just extremely similar  beings. they predict that actual clones will be produced sometime closer to 2010. But if your consider those clones, they are pretty advanced in relation to other labs and/or caves.
624279
this is a difficult one. theres the initial 'soup' of early compounds that spawned life, theres the meteorite theory of cells from other planets gettin a start here, and theres a possible link between both. this may be that chemicals from the many rocks from outer space, the heat of the planet then, and the interaction of all the early substances may have harboured a good environment for a cell 2 form, with a membrane, enclosing some of these compounds within it.
1085010
You mean outside of a biodome? None currently show any promise of sustaining human life in an unaltered state. Most would be too cold, even Mars would be too cold most of the year, the only option is a enclosed biodome, like a space station on a planet, or through terraforming. Terraforming so far would be viable for Mars because of it's proximity and it's like an open ground, there's less in the way (Venus would be very difficult by comparison) outside that the best options appear to be Jupiter's moons such as Titan with a heavy water content and nitrogen.
288876
Yes. They are probably microbes or even smaller nanobacteria. \n\nI have seen the work of Dr. Robert Folk at the University of Texas, who examined the Martian meteorites found in Antarctica and found possible fossil evidence of nanobacteria. Many biologists are not convinced that nanobacteria (which are measured in nanometers) even exist and argue that they are too small to contain the functions of a living cell. The topic remains controversial.   \nHere is a page discussing the biological controversy (there are some geological controversies as well):\nhttp://serc.carleton.edu/microbelife/topics/nanobes/index.html\n\nHere is the NASA page describing the findings:\nhttp://nssdc.gsfc.nasa.gov/planetary/marslife.html
997050
Sure there are. There are many as-yet undiscovered species within out own world. Remember also, that we are but one of thousands of "species" living on the earth. While not provable at this point, given the vastness of our universe, it is likely that there are other forms of life elsewhere. I'd not imagine "little green men" as much as simple-cellular forms.
82957
Maybe. It seems that in a universe filled with billions of galaxies, each with billions of stars, each with a potential to have a planet with life around it, that at least a few other planets would have to have life. It is not reasonable to suppose this is the only one where this ever happened. \n\nHowever, you asked about "creatures like humans". This is possible, but no where near as likely as there simply being "life" on other planets. The forces of natural selection ("evolution") can develop life in a myriad of possible shapes, and there is no guarantee that human-like lifeforms will evolve anywhere else. By some points of view, it is virtually impossible since a great many events happened over billions of years that resulted in us looking like we do. There might be life out there, and even intelligent life, but it is probably very different from us. \n\nHowever, another way to look at it finds the possibility that there is life like humans out there. Think about this: how many ways are there to get around: swimming, crawling, brachiating (swinging from trees), flying, walking. Maybe there are a few more that we don't see on Earth. Legs are one of the best ways of getting around, so it seems likely that, if there are many different worlds with life, a large proportion of those worlds have creatures with legs. This same logic applies to arms and hands--how many effective ways are there for manipulation of objects? Tentacles, cilia-like graspers, lobster claws, hands, and probably more. Still, something like hands at the end of flexible or jointed extensions like arms is a very good means of allowing a creature to grab things and shape them, so it seems likely that something hand-like will also appear. And then there are the obvious advantages of having the head on top of the body, for standing upright, for having two eyes set horizontally, etc... \n\nWhat I am getting at here is that there might be a million million ways that lifeforms can be shaped, but perhaps there are only a limited number of forms capable of inventing and building cities or ships or plows etc... Since the ability to create these things have such obvious advantages, life might often be "channeled" by the force of natural selection into the forms that allow technology, and therefore a human-like form might be seen more than just here on Earth.
220501
Considering that we are of the same stuff that all other life on Earth is made of, it seems very unlikely.  Of course that does not eliminate the possibility that life on Earth was seeded from some outside source 2 billion years ago.
386417
Every being on earth's appearance is determined by their lifestyle/environment/etc, up to a point, and I wouldn't expect anything else for life forms of other planets.\n\nAre we talking about other carbon-based life forms, or are they methane-basted? Or ethane-based? Or, why not, even hydrogen-based? What kind of environment do they live in? What type of atmosphere does their planet have? What is the climate?\n\nAsking what an alien like is sort of like asking what an animal looks like. I bet there are so many different types...\n\nOne failing of a lot of science fiction is that, in the designing of the aliens, they just wanted to make them as weird a version of humans as possible, without thinking about what sort of biology their home planet would naturally produce.
632331
Yes, but not only that, planets in this galaxy, and also planets or moons in our solar system. Intellegent life, perhaps a great deal more rare.\n\nIn our lifetime (well, you younger ones anyway), I predict we will learn that Europa, Titan and possibly other moons sustain simple life forms. Extreme biology on earth has demonstrated that all simple life needs to survive is an energy source. It doesn't have to be the sun. It can be thermal venting or friction from plate techtonics. It exists under the ice in Antarctica and miles under the sea in pitch blackness.\n\nLife- ubiquitous. Intelligent life - far less so.