Photo Credit: A. Passwaters/Rice University based on original courtesy of NASA/JPL-Caltech at

The question of whether or not life exists elsewhere in the universe has been examined in countless ways, and much of the discussion depends on knowing how rare an occurrence life is. When it does arise, how likely is it to evolve into an intelligent species? We’re now nearly certain that there are at least hundreds of other planets in our galaxy (based on our best instrumentation and scientific rationale) and assume that the number is actually higher than that by orders of magnitude, but we still don’t know the odds of life arising in any given place, let alone intelligence. And sometimes rather oblique investigations make the issue even murkier.

Although we can imagine forms of life composed of different elements, Earth life is based on the element carbon. Without carbon-based molecules, there would be no life as we know it. So is carbon a common element on extraterrestrial planets? If so, we might have high hopes that carbon-based life would have arisen elsewhere. The problem is that many scientists who investigate planet formation feel that Earth shouldn’t have large amounts of free carbon that isn’t locked into the planet’s core. So some researchers from Rice University have theorized that Earth must have been hit by a Mercury-type planet something like four billion years ago and absorbed the doomed planet’s carbon into Earth’s upper mantle and crust, where it could eventually be used for the evolution of life forms. If that’s true, and if carbon-based life couldn’t arise any other way, then the rarity of that exact type of collision means that the number of planets hospitable for our kind of life would be equally rare.

Another couple of researchers at Cornell University have approached the question of life’s scarcity in a completely different way. They’ve calculated the rate at which genetic material (like DNA) increases in complexity through natural evolution, reasoning that if you work that rate backward you can figure out how long ago the most basic life forms came into being. According to their calculations, it took far longer than we’ve previously thought for life to arise and ultimately evolve into intelligent beings—nearly ten billion years, in fact. Ten billion years ago is before the existence of the solar system, so they propose that life arose elsewhere and travelled to Earth by meteorites. But if it really does take that long for intelligent life to develop, then we shouldn’t be expecting visits from advanced aliens anytime soon. They’ll all be at about the same stage of evolution as we are—we may even be among the first intelligent species to arise.

What would it mean to us if we do turn out to be alone in the galaxy? On the bright side, we won’t go out into space and face a slew of hostile races eager to kill us off, as in Starship Troopers by Heinlein, and the John Scalzi Old Man’s War series. But it would also mean that we’ll never find companionship beyond our own kind, never get fresh perspectives on art, music, love, or the meaning of life. We’d never get a chance to learn from others with very different experiences. Even worse, if the number of planets with carbon-based life turns out to be near zero, then it will also be nearly impossible for us to find new worlds that are hospitable to us and our fellow Earth species, which means we’ll have to terraform every planet we encounter before we can colonize it, a process that could take thousands of years.

Much as I hate the thought that venturing out into galactic space would bring humanity into conflict with other races, I really hope that life isn’t a rare thing in the cosmos, and that we’re not the only intelligent beings. A universe with no inviting planets or potential friends would be hostile indeed.


I’ve posted recently about the search for extraterrestrial intelligence and the (so far) lack of success. But why are we so focused on intelligence? Wouldn’t it be awesome enough just to discover life elsewhere in this vast universe? Jumping high-five awesome? For some reason most of the attention and all of the angst has been centered on the idea that there might be other species of beings out there that might be interested in us for the purposes of a) contacting, or b) conquering. Yet the search has come up empty. Well, maybe intelligent life is as rare as a politician with his hands in his own pockets, and there are lots of reasons it could remain hidden from us, but the discovery of any kind of life inhabiting other solar systems would be cause for celebration.

This week NASA announced a brand new coalition of scientific endeavours to be known as NExSS (Nexus for Exoplanet System Science). Each of the partner projects will focus on different aspects of the search for extraterrestrial life including refined spectrometers better able to detect Earth-like planets, how planets form and where, the potential habitability of exoplanets (from a human perspective), tidal dynamics, how organic elements reach planet surfaces, and a lot of other topics.

I love this idea, and not just because of its geek-cool acronym. The practical side is that the more we know about how habitable planets get that way and how life arises and survives elsewhere, the better we can understand the challenges of our own planet and maybe even find solutions to the damage we’ve done to its ecosphere. God knows, we need all the help we can get in that department. But beyond the practical is the pure stomach-tingling thrill of a treasure hunt. Finding carbon-based life on an exoplanet would be like finding a long-lost cousin you never knew you had (who doesn’t know about all the skeletons in family closets). No, bigger than that—it would be like living all your life in a sheltered village and suddenly finding out that there’s a whole world just beyond the trees. There was a hint of that when the first exoplanets were discovered in the mid 1990’s, but the confirmation of extraterrestrial life would ramp that excitement up to a whole new level. Think of all of the new questions, and the answers, and…more questions.

Does carbon-based life require DNA? A cellular structure? Does it always follow a birth-to-death life cycle, or could there be forms of life that are effectively immortal? What about sex—we’re always fascinated by sex.

What if we find life forms that aren’t based on carbon? There’s been speculation, but proof would really upset the bioscience applecart. And that could be a good thing. Sometimes the best way to advance is to throw everything you’ve known up in the air and see what new patterns form when it lands.

Whatever we learn about life elsewhere is bound to open our eyes to secrets our own planet has yet to offer up, because I’m certain we haven’t yet found every type of life the Earth has produced, hidden in the depths of the ocean or the planetary crust. Not to mention other bioscience implications like the discoveries of new potential medicines. Learning how extraterrestrial life copes with unique or harsh conditions might teach us how to protect ourselves from nasty surprises like cosmic ray bursts or asteroid strikes, too.

Most of all, I love this plan because the discovery of life elsewhere would give us somewhere to go and a reason to get there. The human race is at its best when we have goals that inspire us, nearly unattainable heights to climb. A treasure just beyond our reach that requires us to dig deep within ourselves and strive together in community.

We could really use something like that right now, and NExSS just might point the way.