Question

What is a ‘sulfur-based’ organism? Did I step in a pile of science fiction? Please clean up my brain on this one.

While many organisms may be dependent on sulfur for their biological processes (sometimes misnamed "sulfur-based" when intended "sulfur-dependent"), none to date have been discovered that do not depend on carbon as well. Furthermore, we have yet to observe any life form that is not entirely carbon-based, that is, the backbone atom of its living systems being carbon. Despite these observations, scientists have often speculated that life could be based on an element other than carbon. Silicon, being the lightest element with an electronic structure analogous to that of carbon (having a half-filled outer shell with 4 unpaired electrons), is the most likely candidate. Since both silicon and carbon are tetravalent, it has been thought both molecules retain the ability to comprise large molecules and chains necessary to create complex biostructures (hair, skin), catalysts (enzymes), and information molecules (DNA, RNA) required of life. However, the possibility of silicon-based life forms is probably more science fiction than reality—the chemistry of silicon is actually quite different than that of carbon. For example, methane (CH4), is stable at room temperature and only burns in the air if ignited. Silane (SiH4), on the other hand, reacts explosively when exposed to the oxygen in the air. Likewise, larger polysilicon molecules show this marked difference in reactivity versus carbon. In addition, the observed abundance of carbon relative to silicon in the universe suggests that it would be the chemistry of choice for the origin of life in any newly formed planetary system.
May 1, 2002