Leroy Chiao is a former NASA astronaut. During his 15-year career, he flew four missions into space, three times on space shuttles and once as the copilot of a Russian Soyuz spacecraft to the International Space Station. On that flight, he served as the commander of Expedition 10, a six-and-a-half month mission. He has performed six spacewalks, in both US and Russian spacesuits, and has logged nearly 230 days in space. The opinions expressed in this commentary are solely those of the author.

(CNN) NASA announced this week exciting results from a spacecraft observing Saturn's moon Enceladus and Jupiter's moon Europa. Equipment on the Cassini probe detected some of the required conditions and building blocks for life on both moons.

For those like myself, who thrill at any discovery that suggests Earth's creatures may not be alone in the universe, the findings capture our imagination anew.

But does Cassini bring our imaginings closer to reality?

Let's look at what the discovery shows:

Cassini dove through plumes erupting through the icy surface of the oceans of Enceladus. Plumes have also been observed by the Hubble Space Telescope (HST) erupting through the solid ice surface of Europa's ocean. And previous thermal measurements by the Galileo spacecraft showed that the recent Europa plumes appeared directly over a hot spot in the moon's ocean.

We can infer that that these plumes are due to hot eruptions on the ocean floors.

On Earth, scientists have detected life near the points of deep ocean eruptions. It was long thought that the environment at such great depths was far too cold and hostile to support life. But it turns out the eruptions provide enough heat to support "extremophile" microorganisms — life where we didn't think it could exist. Thus it is reasonable to expect that the same thing could happen on other planets or moons.

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During its Enceladus dives, Cassini determined that the plumes consist mostly of water. But the spacecraft also detected hydrogen, carbon dioxide, methane and other chemicals. Hydrogen and carbon dioxide in the water could support a metabolic process called "methanogenesis."

In this process, a microorganism uses carbon dioxide and hydrogen to produce energy and methane as a byproduct. So while Cassini did not find life per se, the data show that some of the critical chemical building blocks are there.

Even more exciting is the fact that these observations were made within our own solar system. It is a short step, then, to predicting that conditions for life are likely in many places in the universe.

While it would be very exciting to find actual microbial life on one or more extraterrestrial worlds, it would be a far cry from finding intelligent life. Even so, such a microbial discovery would still greatly open up the possibility of intelligent life elsewhere in the universe.

And this is why the Cassini announcement sparks the imagination so.

Humans have been fascinated by the possibility of extraterrestrial life ever since we became aware that there are other worlds out there. This has landed scientists in hot water, including the namesake of the Galileo spacecraft, who in the 17th century was placed under house arrest for daring to suggest that not only was the Earth not the center of the universe, but that it was not even the center of our solar system.

Could there indeed be intelligent life out there? My spaceflight experiences have made me think about this quite a bit. My personal belief is that there is intelligent life all over the universe. The problem is that the distances in space are so vast, it is unlikely we will ever find each other.

The nearest other intelligent life could be over 100 million light years away. So even if we figured out how to travel at the speed of light, it would still take 100 million years or more to get there.

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If you assume that the Big Bang theory is correct and that the universe all started at one instant, and if you assume that Earth and its inhabitants are "average," then we will never find each other. This is because life here on the Earth will likely end before we have the technology to find life light years away. And for the same reason no other life will then find us either.

Indeed it seems plausible — even likely — that life starts at places in the universe even as it simultaneously ends in other places. As belief systems go (and this is mine), this one is actually quite liberating once you accept it: Since we are unlikely to encounter any other life or life form than the ones we have now, we ought to make the most of what I call our One Orbit, our one life.

Cassini's discovery helps us to do that. It helps expand our knowledge of our corner of the universe and dream about the awesome potential that is out there beyond. UnIike those who persecuted Galileo, we are enlightened enough now to have an open mind to all possibilities. And to keep on dreaming, as we live our own lives to the fullest.