Aliens Around Us?

I have posted several times on this blog about the possibility of life existing elsewhere than just on Earth. It's a subject that fascinates me and one for which we inch closer to an answer, each year. One important development in the search is that scientists are increasingly broadening the definition of life. Recent discoveries of strange life forms right here on Earth have pushed scientists to ponder the possibilities of alternative kinds of life. NASA's current definition of life is “a self-sustaining chemical system capable of Darwinian evolution.” That's much broader than the thinking was, just a few years ago.

In fact, some microbiologists have proposed an even broader definition of what they have dubbed “lyfe”—trying to become more open to alien possibilities. Lyfe has been proposed by them to have four qualities: it (1) draws on energy sources in its environment, (2) grows through replication, (3) can adapt to a changing environment, and (4) learns and remembers information that it acquires from that environment. Gone are the former criteria that life must be carbon based or even require liquid water.

Additional open-minded possibilities about lyfe are that—other than on Earth—its pace might be far slower or faster than life forms as we know them; thus making it difficult to even notice that it could be lyfe. Furthermore, could lyfe use energy sources that life does not? For example, bacteria have been discovered in deep Earth mines that do not use the sun's energy, but get their energy from radioactivity. Could there even be something that might be called “sub-lyfe,” which doesn't have to meet all four of the above criteria? Or even “super-lyfe,” which surpasses the four criteria? It's possible, furthermore, that a form of super-lyfe might look upon us humans (and all our fellow Earthly life forms) as we do upon crystals; or viruses, which are a form of not-quite-life, (requiring a living biological cell to invade and hijack its life functions).

When pondering the possibilities of life (or lyfe), other interesting questions come to mind. Are there ways to store information, other than by DNA? Where is the boundary between lyfe and non-lyfe? Must lyfe possess sharp, physical boundaries?

This past July, three missions left Earth for Mars—from China, the United Arab Emirates, and the US. They are all aimed at the next step of characterizing the nature of our fellow planet Mars—one that long ago had oceans and an atmosphere somewhat like Earth. The US and Chinese missions are both landers that will seek signs of current or past life there. Should we redefine their quest as one of looking for lyfe?

For future projects NASA is planning missions to Europa—a moon of Jupiter—and Titan—the largest moon of Saturn—both of which have the best chance of nonEarth life (lyfe?) in our solar system. By opening up to the definition and possibilities of lyfe, those undertakings may be more successful and unambiguous.