In some ways, our biologists are hampered by having only one “scheme” to study. Since all extant life on Earth descended from the same primordial unicellular organism (perhaps 3.5 billion years ago), we all share a remarkably similar biochemistry, even in details. It is difficult to imagine what other systems would be possible, and how fundamentally different they might be. This also means that as we search space for signs of extraterrestrial intelligence, we tend to concentrate on organisms like us. For the most part, we assume that they, too, will be carbon-based, and use water as a solvent for organic chemistry. Silicon and ammonia have been proposed as alternatives, though the available chemistry doesn’t appear as rich. (See Wikipedia’s article on alternative biochemistry for more information.) Then, too, organisms with this alternative biochemistry still would be rather similar to Earth-based life. What other possibilities could there be? Scientists and science-fiction writers have tackled this question for generations.
Scientists in Germany speculate about life in spirals of dust in outer space. Electrically charged dust immersed in plasma (ionized gas) can produce crystals and spirals. According to a New Scientist article, a simulation suggests double-helices could form as well. In addition, two stable states suggests that information could be “encoded” in these structures. If these structures exist, are stable, and can replicate (perhaps by inducing the surround dust to adopt the same pattern), a self-replicating system that could give rise to life would exist—indeed, many would argue that such a self-replicating system were alive. The researchers speculate that the rings of Saturn or Uranus might be regions to find such spirals.
Of course, this is all hypothetical, but I find it fascinating, nonetheless.