Extraterrestrial Life --"Alternative Biochemistries"
- URL to an interesting article
Alternate biochemistries? Maybe that's what's wrong with Sizzler.
Seriously, how would we recognize life in an ammonia cloud? How would we
recognize life on an icy world if its tempo was 1000 times slower than ours?
First few paragraphs
In his famous lecture, "_Life in the Universe_
(http://en.wikipedia.org/wiki/Extraterrestrial_life) ," Stephen Hawking observed that what we normally
think of as 'life' is based on chains of _carbon atoms_
g-edge-on-galaxy-the-engines-of-life.html) , with a few other atoms, such
as nitrogen or phosphorous. We can imagine that one might have life with
some other chemical basis, such as silicon, "but carbon seems the most
favorable case, because it has the richest chemistry."
Several eminent scientists think otherwise, that life in the universe
could have a myriad of possible biochemical foundations ranging from life in
ammonia to life in hydrocarbons and silicon. Silicates have a rich chemistry
with a propensity for forming chains, rings, and sheets.
One of the founders on modern genetics, Cairs-Smith, argued that layers of
crystalline silicates functioned as a primitive form of life on early
Earth, before they evolved into _carbon-based life_
The Earth was formed largely out of the heavier elements, including carbon
and oxygen. Somehow, Hawking observes, "some of these atoms came to be
arranged in the form of molecules of _DNA_
nconclusive.html) . One possibility is that the formation of something
like DNA, which could reproduce itself, is extremely unlikely. However, in a
universe with a very large, or infinite, number of stars, one would expect
it to occur in a few stellar systems, but they would be very widely
Other prominent scientists have warned that we humans may be blinded by
our familiarity with carbon and Earth-like conditions. In other words, what we
’re looking for may not even lie in our version of a “sweet spot”. After
all, even here on Earth, one species “sweet spot” is another species worst
nightmare. In any case, it is not beyond the realm of feasibility that our
first encounter with extraterrestrial life will not be a solely
Alternative biochemists speculate that there are several atoms and
solvents that could potentially spawn life. Because carbon has worked for the
conditions on Earth, we speculate that the same must be true throughout the
universe. In reality, there are many elements that could potentially do the
trick. Even counter-intuitive elements such as arsenic may be capable of
supporting life under the right conditions. Even on Earth some marine algae
incorporate arsenic into complex organic molecules such as arsenosugars and
Several other small life forms use arsenic to generate energy and
facilitate growth. Chlorine and sulfur are also possible elemental replacements for
carbon. Sulfur is capably of forming long-chain molecules like carbon.
Some terrestrial bacteria have already been discovered to survive on sulfur
rather than oxygen, by reducing sulfur to hydrogen sulfide.
Nitrogen and phosphorus could also potentially form biochemical molecules.
Phosphorus is similar to carbon in that it can form long chain molecules
on its own, which would conceivably allow for formation of complex
macromolecules. When combined with nitrogen, it can create quite a wide range of
molecules, including rings."
(Madness takes its toll. Please have exact change)
[Non-text portions of this message have been removed]