"That's 500 billion planets out there, and bear in mind there are 100 billion other galaxies. To think this [the Earth] is the only place where anything interesting is happening, you have got to be really audacious to take that point of view."
Seth Shostak, SETI senior astronomer
Some leading astronomers are quite confident that mankind will make contact with intelligent alien life within two decades. The search for extraterrestrial life will leap forward next year when NASA launches the Kepler space telescope. The instrument will be constantly scanning the same 100,000 stars over its four-year mission with the exciting objective of discovering Earth-sized planets in the habitable zones around suns.
This will allow SETI to hone in on where the odds of life are possibly greatest. Currently, SETI’s mission to find life on other planets is like trying to find the proverbial needle in a haystack. But now, whenever Kepler identifies planets most likely to sustain life, the team at SETI will be able to focus in on those solar systems using deep-space listening equipment. This will be a huge upgrade from their present work of randomly scanning the outer reaches of space for some kind of sign or signal. Also, upping the ante, is the recent discovery of Earth-like planets outside our solar system, which has led astrophysicists to conclude that Earth-like planets are likely relatively common in our galaxy.
"Everything has caused us to become more optimistic," said American astrophysicist Dr Frank Drake in a recent BBC documentary. "We really believe that in the next 20 years or so, we are going to learn a great deal more about life beyond Earth and very likely we will have detected that life and perhaps even intelligent life elsewhere in the galaxy."
However, some astrophysicists have warned that we humans may be blinded by our familiarity with carbon and Earthlike 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’s 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 carbon-based occasion.
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 arsenobetaines. 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.
So what about water? Isn’t at least water essential to life? Not necessarily. Ammonia, for example, has many of the same properties as water. An ammonia or ammonia-water mixture stays liquid at much colder temperatures than plain water. Such biochemistries may exist outside the conventional water-based "habitability zone". One example of such a location would be right here in our own solar system on Saturn's largest moon Titan.
Hydrogen fluoride methanol, hydrogen sulfide, hydrogen chloride, and formamide have all been suggested as suitable solvents that could theoretically support alternative biochemistry. All of these “water replacements” have pros and cons when considered in our terrestrial environment. What needs to be considered is that with a radically different environment, comes radically different reactions. Water and carbon might be the very last things capable of supporting life in some extreme planetary conditions.
At any rate, the odds of there being some type of life somewhere out there are good. As for intelligent life, well, that will depend on the definition of intelligence. There are a lot of other intelligent species here on Earth besides humans, that we don’t generally regard as such. In spite of many Star Trek episodes to the contrary, the odds of alien life forms having evolved to talk, look and act exactly like super hot humans are slim to none. If life is out there, it will have evolved according to it’s particular niche in the universe and will likely be quite foreign to us in the way it looks, communicates and thinks. We might not even be able to recognize hypothetical life forms as alive in the sense that we understand life. In fact, it would be more “miraculous” if we could effectively communicate with extraterrestrial life than to find that it exists. From that perspective, even if there are other life forms out there, we’d still be alone in the universe. Of course, that doesn’t mean we should look for the answers.
Posted by Rebecca Sato.