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Earth May Harbor a Shadow Biosphere of Alien Life
An anonymous reader sends us to Cosmos Magazine for a speculative article arguing that a 'shadow biosphere' may exist on Earth, unrelated to life as we know it. If such non-carbon-based life were found here at home, it would alter the odds for how common life is elsewhere in the universe, astrobiologists say. "The tools and experiments researchers use to look for new forms of life — such as those on missions to Mars — would not detect biochemistries different from our own, making it easy for scientists to miss alien life, even if [it] was under their noses. ... Scientists are looking in places where life isn't expected — for example, in areas of extreme heat, cold, salt, radiation, dryness, or contaminated streams and rivers. [One researcher] is particularly interested in places that are heavily contaminated with arsenic, which, he suggests, might support forms of life that use arsenic the way life as we know it uses phosphorus."
Not an expert in biology, but unless these contaminated areas have been contaminated for a very long time (read tens of thousands of years), and are quite large, the chances for life to have sprung up seem very, very slim. Current life needed millions of years to gain a firm foothold and start building up complexity. Lucky meteorites aside, starting from zero is bound to be hard.
If the experiment succeeds (here or elsewhere), and something "life-ish" is found, the results will still be tricky to classify. Can a given chemistry lead to increasing complexity, or is it just a dead end? Without hindsight, this seems like a very difficult question.
You both have a point. The question is, where do you draw the line at what is life? Rocks may not have DNA or intelligence, but they do form, change, multiply and there's a recognisable process for destroying them. In a sense, rocks are a lot like the most basic forms of life that ever formed.
Let's be a little more serious now. Rocks around here probably won't ever advance beyond mimicking some very shaky comparisons to the most basic forms of life. But that doesn't stop us wondering if we're just seeing it on too small a scale to make that judgment. Perhaps it's safer to treat rocks as a failed attempt at life, one that happens too slowly to ever get beyond basic chemical reactions and simple molecular structures.
If it weren't for carbon-based life, who knows?
http://www.newscientist.com/article/mg19826533.600-early-life-could-have-relied-on-arsenic-dna.html tried looking up some examples of non carbon based life on earth that I'd heard of but couldn't find any however the ecology of undersea volcanic vents pretty much threw most ideas about heat tolerance and toxins being a problem out of the window.
Build a Man a Fire, and He'll Be Warm for a Day. Set a Man on Fire, and He'll Be Warm for the Rest of His Life.
You both have a point. The question is, where do you draw the line at what is life? Rocks may not have DNA or intelligence, but they do form, change, multiply and there's a recognisable process for destroying them.
Rocks do not have gaseous exchange (breathing) nor reproduce (cracking a rock to make two is _not_ reprodction). However, there is no definition of life that fire cannot meet, which the mule can. In other words, any non-contrived definition of life that includes the mule must also include fire. Here is a very basic explanation: http://simple.wikipedia.org/wiki/Life
It is dangerous to be right when the government is wrong.
You can form chains or rings of around 6 sulphurs (with oxygen), but carbon can be found in chains of 30+ atoms and in multiple ring systems.
It's very difficult to grasp how large the isomer spaces are - and how quickly they grow, but a recent guestimate I made was that if a program (molgen) can enumerate all possible C10H16 molecules in 2 seconds, and all C13H22 in 2 minutes, then it would take 2 days for C18H36 and 1 billion years for C36H72...
Also, there are 25,000 C10s and 9 million C15s. So the sheer number of possible carbon compounds argues that carbon is the only likely candidate.
As the Zen practicioners are indistinguishable from day-dreamers such as my 9 year old son, your refutiation is meaningless.
Not really. They've studied the brains of Zen practitioners in meditation and have determined that Zen meditation actually increases brainwave significantly -- more so than even normal daydreaming.
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Neutral is what doesn't dissolve you.:) It is not neccessarily aqueous pH7 for everything.
The most likely alternate chemistry for life though, is carbon based, but using ammonia instead of water. At above about 70 psi, and somewhere below zero celsius it has a liquid range and chemistry similar to water. Given a larger, colder planet than earth with a thick atmosphere, life in liquid ammonia is the most probable option.
I'm guessing that wasn't on their radar screen...
I didn't find it on Google, but about 30 years ago I read an account of a creature like a giant sand dollar that was dislodged from the deep ocean by an undersea earthquake. I can't verify it until I find a reference, but I recall that the scientist examining it found that it was largely silicon, hydrogen, and sulphur (and decayed rapidly giving off H2S). His theory was that it was silicon based life - and that its chemistry required deep ocean temperature and pressure to remain stable. (Note that there are carbon based ocean creatures able to process silicon to create SiO2 structures.)
Actually, a rock does grow, given the right conditions. Specifically, a rock exposed to supercooled rock vapour will have said vapour condense and freeze on its surface, resulting in a bigger rock.
Forget magic. Any technology distinguishable from divine power is insufficiently advanced.
I think you are absolutely right. It seems that many people cannot understand how special the carbon atom is. They assume that our life being based on carbon wouldn't exclude life based on other atoms somewhere else.
Not true. There's a special, unique property in the carbon atom orbital structure that allows very complex structures. No other atom has that quality, unless some basic constants of the universe were changed. It's like comparing a set of Lego blocks with a box of marbles.
The same goes for temperature, to get life one needs a liquid solution that lets molecules interact. With a solid there's no interaction, with a gas the molecules don't stick together, so one needs a liquid for transporting the elements of life. If a planet is too cold or too hot life will not appear. These are some basic limits on the physics and chemistry that will allow for complex chemistry to gradually evolve.
And the funny thing is that we have both theory and experiment telling us that life isn't very common in the universe. We haven't found any sign of life in either Mars or Venus, which a hundred years ago many people thought would certainly have life. If planets like Venus and Mars, that are very close to the Earth in their characteristics, didn't create life, then one should assume that our position is very special.