GALEX decommissioned: What happens to abandoned space probes?

The pink slip was delivered at 3:09 p.m. EDT on Friday in Dulles, Vermont. The order: decommission Galaxy Evolution Explorer.

And so, after about a decade of use, the power was flicked off on GALEX.

The Earth-orbiting spacecraft – which had been cut from NASA’s budget in February 2011 and had survived off funds from the California Institute of Technology – had racked up a sizable roster of discoveries during its mission, observing the teenage-stage of galaxy growth, a black hole consuming a star, the presence of new stars around dead galaxies, and insights into the nature of dark energy.

The spacecraft will remain in orbit for at least another 65 years, floating glumly and uselessly around the Earth. Then it will fall back toward the planet, burning up as it re-enters the atmosphere, doing one last service as a “shooting star” on which a celestial-looking child might make a wish – just as writer Ray Bradbury, in his 1951 story Kaleidoscope, imagined an unlucky, falling astronaut as the object on which a small Illinois boy pins all his hopes. 

GALEX’s sad, lonely end is typical. Few objects launched into space have hope of seeing Earth again. Unless, of course, there are people on board, that brave object is designed not to come back to us, but to serve its mission and then remain out there as a teeny record of human ingenuity and curiosity floating through an impassive universe.

Some of these explorers, like GALEX, will meet a sudden end. Our space record is packed with casualties – spacecraft that made fatal landings and the dust of which has been received neatly into the universe. There was Russia’s Venera 3, a Venus-bound probe that crashed into the planet in 1966. And there’s the US’s Mars Climate Orbiter, which in 1998 made a faulty entry into the planet’s orbit and fizzled up in the unfriendly atmosphere.

But for other spacecraft, the end is more uncertain, more a long wait for something, anything, to happen. Other Venera probes (Russia launched some 16 of them) are presumably still somewhere on Venus, their batteries shot. And on Mars, NASA's Spirit Rover stopped communicating in 2010; since then it has lingered hopelessly there in the Martian desert. Opportunity, its twin rover, is still chugging along, sending back new information as it waits for something to go wrong. “Every day is a gift,” said John Callas, of NASA’s Jet Propulsion Laboratory, of that rover, earlier this month.

Curiosity rover – which landed on Mars last summer – has a mission of one Mars year, or some 687 Earth days. Perhaps it will outlast its warranty. But eventually it will join the other decommissioned, powerless rovers on the Red Planet, waiting dully for something to happen to it, ever so slowly eroding and gathering Martian dust.

Perhaps the loneliest of ends is reserved for the most far-flung objects, which quietly, without complaint, recede into the universe.

In Bradbury’s Kaleidoscope, a spacecraft splinters midflight and sends its human cargo floating through the terrible emptiness, waiting for something that will put an end to it all. And so they fall with “vague acceptance,” with “varying degrees of terror and resignation,” with the knowledge that “nothing could bring them back.”

The falling astronauts in that story enjoy the benefit of a reasonably short lifespan. But for the (mercifully non-sentient) space probes, the wait is much longer, possibly forever.

Voyager 1, which is now at the outskirts of our solar system and preparing to depart for the rest of our galaxy, and Voyager 2 will run out of fuel in about 2020. After that, the siblings will drift through space, waiting, "each going to a separate and irrevocable fate."