The discovery of active water geysers on Saturn’s moon Enceladus is exciting on many levels. It drives home the startling new recognition that most of the oceans of the solar system are not on Earth but are on other worlds, all (so far as we know) way out beyond the asteroid belt.
And it raises the tantalizing thought, already growing in intensity in the last decade or two, that these oceans — just like the deep oceans of Earth — may not be the sterile, boring empty voids scientists once thought. We’ve been amazed by the teeming biochemistry around deep ocean vents on Earth, and this may be only a foretaste of future amazements when we get access to otherworldly oceans.
Enceladus has now offered, on a space platter, the easiest-so-far way to examine directly the composition of such oceans. We don’t have to drill or melt our way through a hundred miles of an outer ice shell, as on Jupiter's moon Europa, or fight our way down through and back up through a thick atmosphere such as found on Titan, Saturn's largest moon.
We can go out there to Enceladus and pick up the samples in deep space, delivered conveniently by the geyser system that appears to be driven by the same heating process — gravitational flexing — that created the Enceladus liquid water pools in the first place.
The astonishingly successful Stardust mission shows the way. During a seven-year voyage, the Stardust spacecraft flew through a comet’s dusty haze and brought back samples now being studied by planetary scientists. Initial indications are that the materials caught by the aerogel collectors consist of 20 percent or more of organic molecules, probably produced by purely chemical processes but fascinating nonetheless as new clues to the early history of life on Earth and on any other world sprinkled with comet dust.
An aerogel-equipped spacecraft could be dispatched to the Saturn system to make repeated passes over Enceladus (the geysers don’t seem to be permanent features) while opening Stardust-like collection grids. Bonus passes through the upper atmosphere of Titan and the outer rings of Saturn might also be possible. And we may get even more potential targets as the Cassini probe that discovered these wonders continues to explore.
The mission would be harder and longer than Stardust, but not discouragingly so. With a nuclear power source, the probe — named Starfount or Starspring or some such — could take 15 to 20 years to make the round trip, including perhaps the first-ever Jupiter flyby on an inbound trajectory. An opportunistic collection phase through the plumes of sulfur volcanoes on Io, another of Jupiter's moon, may not be out of the question.
NASA could conduct this mission, or the European Space Agency (which has already dispatched a 15-year mission to orbit and land on a comet), or Japan (whose Hayabusa asteroid mission serves as stirring example of bold innovation), or even a reborn Russian space program (with its unique space nuclear power experience) — or an alliance of elements from these and other spacefaring parties.
Why water matters
Our fascination with water in the solar system isn’t "pure scientific curiosity" or the desire to import astro-Evian drinkables. In large part it’s fueled by startling revelations in recent decades of the fundamental nature of life on Earth.
Less than a lifetime ago, scientists looked out on the rest of the solar system and considered the physical conditions they observed or calculated for the other worlds. Since it was so different from those that we live in on Earth, the inescapable conclusion was that "life as we know it" was highly unlikely anywhere else.
But now we have learned that this judgment was seriously in error, and the evidence was found right here on Earth. The error was literally superficial — we had made assumptions about “life on Earth” before we had found where most life on Earth was, and had been for billions of years: deep underground, and on the floors of the oceans, and, perhaps, even in Great Lakes-sized pools under ice caps.
Away from sunlight, these life forms use chemical and thermal sources of energy to drive their metabolism. They still require liquid water, but at temperature extremes and degrees of chemical contamination once thought more than adequate to assure sterilization. But like the proverbial bees that kept on flying when self-styled aerodynamics experts had proved they couldn’t, the masses of underground organisms kept on living. Estimates vary, but they might account for 90 percent or more of the living biomass on the planet, by weight.
And with this expanded range of life right here on Earth, what does this imply for "life" elsewhere? The other worldly environments now being discovered by space probes and sharper-sensed ground-based instruments are so similar to environments where we now realize most of Earth’s biomass happily lives, the old conclusions have been thrown out the airlock window.
But while we know we were unjustified in concluding life could not exist out there — we so far have no clear evidence that it does, or ever did. The only proper response is to extend our senses outwards and find out.
What it means for us back on Earth
But why? Do improved science textbooks and even exciting news headlines offer rewards for the effort needed? If there are signs of life — past, present, or even future — on Enceladus, or Europa or Titan or even below the bitterly-cold ice shells of Pluto or the newly discovered Sedna, what does that benefit us?
The fundamental and potentially infinite benefit is that we, too, are "life," with our particular biochemical processes that allow us in a time-tested but slapdash fashion to grow, survive temporarily, replicate and occasionally stare at the stars. To understand this process that briefly keeps each of us alive, we study the examples we have — ourselves and our cousins from the same crèche — and speculate. But examples from another crèche could show the range of possibilities that was irreversibly narrowed here on Earth as this particular DNA-based "life form" spread and dominated.
How would another microorganism pass on blueprints for progeny, and how does this other process compare to the successes of "our" life, and how does it fail? How does it repair itself against environmental hazards? Do cells on Europa get cancer? Do they even have DNA-tagged "counters" that on Earth enforce cellular death after so many divisions? Do they allow some — but not too much — replication variation that enables environmentally-driven or behaviorally-driven evolution?
The answers to these and other questions will tell us about the potentialities and design limits of the life processes that comprise ourselves. And that, most definitely, we want to know, and take advantage of.
The "answer book" to all these questions isn’t just lying out there at Enceladus already bound and decoded, for us to go out and pick up and read at our leisure — but pages, or even paragraphs of it, could well be. And this lucky concurrence of watery geysers and of current space capabilities offers a rewarding strategy to do what humans have done, and benefited from, since they became humans: wonder, and then go find out.