It's the end of a mission that took man one giant step closer toward finding out if life exists beyond Earth, CBS News Correspondent Sandra Hughes explains.
For the last eight years, Galileo has been sending back breathtaking pictures of Jupiter and its moons. The spacecraft's look at the icy surface of Europa — one of more than 60 moons — showed there may be water below the ice.
And where there's water, there may be life. In fact, NASA decided to crash the Galileo spacecraft into Jupiter to make sure it didn't collide with Europa and scatter Earth germs all over it.
Galileo was launched in 1989, and it circled Jupiter 34 times. Over the years, its discoveries were so extraordinary, they even inspired an unusual tribute called "Galileo, The Emotional Life of a Spacecraft" in New York. It comes complete with a rock singer playing Galileo.
Megan Halpern, who co-wrote the rock opera, says finding the clues about life in outer space inspired her.
"To know that we are not alone in this universe. That life is common, because if life is on Europa, then it is most likely common," Halpern says, explaining her fascination with the distant moon.
The search for life in our solar system and beyond has long been the province of popular culture. It is also a staple of Hollywood science fiction thrillers.
But now, that search isn't just the stuff of science fiction; it's mainstream science, with NASA leading the way.
"I think a long-term goal that we have is to understand whether our own solar system is unique or common," Charles Beichman, the chief scientist for NASA's Origins program, says. "For the first time in these 2,000 years, we're on the cusp of making this discovery of planets beyond the solar system: habitable planets and even life."
The search starts close to home. Mars is 350 million miles closer to Earth than Jupiter, and it has always fascinated humans — never more so than last month when it came closer to Earth than it has in 60,000 years.
Some gazers of the heavens may expect someone to wave a hello from space, but no one has yet. So we're going after them. Mars is virtually under siege from earthly spacecraft. Two probes are now sending back pictures from the planet's orbit, and two Mars rovers are on the way.
At NASA's jet propulsion lab in Pasadena, Calif., under a watchful little green man, they're still putting the test rovers through their paces — perfecting the software, so when the real rovers start crawling around Mars in January, they won't get lost.
"Could there still be life there?" Beichman asks. "[It's] anybody's guess. Is there fossil life? Quite possibly. Did life on Earth originate on Mars? Could be."
And to further the search for life outside our solar system, last month NASA launched its most advanced infrared telescope yet.
The new telescope should accelerate the discovery of planets outside the solar system. Already, in the past decade, more than 100 planets have been found. And there may actually be billions of planets out there. But what we don't know yet: Can any of them actually support life?
To answer that question, NASA is planning what it calls the "terrestrial planet finder missions." Its goal is to look for other "Earth-like" planets. It's no small challenge. The new telescopes must block the light of nearby stars in order to see the planets around them.
"Imagine trying to find the light of a firefly flying around a searchlight across a continent on a foggy night," Beichman says.
While NASA looks farther and farther out in to space, at the SETI (Search for Extraterrestrial Intelligence) Institute in Northern California, they take virtually the opposite approach. Scientists on Earth are listening to the heavens, using radio telescopes like the ones used in the movie "Contact."
If there's life out there, SETI hopes it's talking. But it hasn't found anything yet.
SETI has been searching for life outside Earth for 40 years, but Chris Chyba of SETI says that so far its researchers have listened to only a tiny fraction of the cosmos.
"We point at a particular star and just listen for a while," Chyba says. "We don't assume that an extraterrestrial civilization would be broadcasting on any particular frequency. We scan a huge range of frequencies."
There's a program that lets anyone join the effort — linking home computers to SETI computers to help analyze the massive amount of data that it generates.
On the horizon is the Allen Telescope Array — 350 radio telescopes in northern California, all working in concert.
"It will allow us to look at a million stars over the next decades," Chyba explains.
To help distinguish between alien-speak and space noise, some of SETI's scientists are studying animal communication here on Earth. For example, they've listened to dolphins, analyzing the repetitive sounds that dolphins make. Using the same type of analysis, scientists believe they could detect intelligent language coming from the stars.
"I think the great importance of that kind of discovery would be simply the determination that there are other civilizations," Chyba says. "Whether, ultimately, we'd be able to translate the signal, who knows? That could be a project that could take generations."
Skeptics, like Peter Ward of the University of Washington, believe it's a project that may never pay off. As a professor of geology, and co-author of the book "Rare Earth," Ward has studied how life has come and gone and come again on Earth.
"We've had catastrophes on this planet over and over that have ravaged the planet," he says. "We've had near-death experiences. My sense is that planets just don't last long enough, as good places to live, long enough to really allow evolution to produce great complexity. I don't think it's going to be very common to find animal equivalents in the Universe."
Ward is in the vanguard of a new breed of astro-biologists, who combine the study of astronomy, biology and paleontology to better understand the cosmos.
He points to the recent discovery on Earth of so-called "extremophiles" bacteria, which survive deep in the ocean with no sunlight.
The bacteria lives in extreme heat and cold. Ward says they are evidence of the the durability of life. But intelligent life? That's another matter.
"There may be life almost everywhere in this galaxy," Beichman says. "But again, is it the kind of life that you can make a TV program out of?"
But Neil deGrasse Tyson, an astrophysicist and the director of New York's Hayden planetarium, says life, even on a small scale, is still life.
At his planetarium, the subject is "The Search for Life, Are We Alone?"
Tyson takes issue with the theory that intelligent life may be unique to planet Earth.
"You look back at any century in the past, somebody is talking about how special we are," he argues. "Any attempt people have made to show that we, humans, life on earth is special, the progress of scientific discovery has demonstrated the opposite."
It's a debate that could be resolved in our lifetime.
"Whether there's life out there or not, in my gut, I think it's likely," SETI's Chris Chyba says. "But you know, you don't think with your gut."