At the time of its 1997 launch, NASA’s Cassini spacecraft was among the most advanced space exploration tools ever built, but after nearly twenty years of exploring our solar system, its fuel reserves are nearly depleted.  Like it or not, Cassini’s days of sending back data about the heavenly bodies littering our celestial neighborhood are numbered… the only question is, what now?

In the past, satellites that have run their course have often been permitted to maintain an orbit around their final destinations.  The Dawn spacecraft, for instance, can still be found orbiting the dwarf planet Ceres it last explored.  Cassini’s space-address in orbit around Saturn, however, presents NASA with a difficult decision to make.

Unlike Ceres, Saturn could be considered a system unto itself.  With fifty-three named moons, and rings composed of tiny particles that could likely have been more, orbiting Saturn would be risky business for a spacecraft that is no longer able to produce any of its own thrust.  Chances are good that the Cassini spacecraft could find its orbit shifted by any number of orbital bodies, eventually sending it into a collision course with the planet or one of its moons.

For the most part, that wouldn’t necessarily matter once the craft is no longer operable, but there’s one more important element to address: what if one of Saturn’s icy moons actually harbors life?

It’s not as crazy as it may sound.  In order for life as we know it to develop on another planet (or moon) we need only common elements found throughout our solar system, and universe for that matter.  Couple those ingredients with some warm water, add a few millennia, and presto – you’ve got life.

Or so we figure.

Saturn is too far away from the sun for its moons to receive sufficient light to melt any water-ice into the liquid water we believe is required for life to develop – but tidal forces within a moon’s core could easily provide just that.  In effect, a moon like Titan, Enceladus, or Jupiter’s Europa, each with scores of frozen water on their surface, could produce enough heat internally to melt the lower portion of the moon’s frozen crust, producing a vast ocean hidden beneath the frigid surface.  Chances are high that each of these moons could resemble a frozen lake in New England’s winter: frozen solid at the surface, but teeming with life beneath.

With this in mind, NASA’s leadership is concerned that allowing Cassini to orbit Saturn freely could eventually result in the spacecraft flying off course and into a moon that is potentially harboring alien life.  Rather than risk contaminating such a discovery with the rubble of a defunct spacecraft, they’ve opted for a more dramatic solution: they’re going to destroy it.

“Cassini has got to be put safely away. And since we wanted to stay at Saturn, the only choice was to destroy it in some controlled fashion,” Earl Maize, an engineer at NASA’s Jet Propulsion Laboratory said in a press conference on April 4th.

Ironically, it was Cassini itself that made the discovery that has led to the decision to destroy the craft.  It was Cassini’s data that NASA used to determine that there were, indeed, salt water oceans hidden beneath the surface of Saturn’s moon Enceladus.

Before signing off for good, Cassini will take one more trip through an uncharted gap between Saturn and its rings.  It will fly through the area at a mind-bending 76,000 miles per hour and gather as much data as it can as it passes through the never-before explored portion of space.

On April 22nd, Cassini will begin its final mission, flying past Titan and through the innermost edge of the planet’s rings, before beginning a spiraled descent into Saturn’s gaseous body, to burn up as it delves toward the most decorative giant in our solar system. The $3.26 billion spacecraft will meet its demise by September, but its legacy will live on in the science devoted to uncovering the possibility of life elsewhere in our very own solar system – a fitting tribute indeed.


Image courtesy of NASA