Nova+Video+Transcript

=Here is the Trascript of the video form the 2:20 mark=

//NEIL deGRASSE TYSON:// So, what is required to get it all started? Here on Earth, the chemistry of life relies heavily on the element carbon. Carbon is one of the most versatile elements, each carbon atom can hook up with one, two, or three or four other atoms. It can even link up with other carbon atoms creating long chains or rings. Throw in a few other elements, and you've got amino acids, the ingredients of proteins, the building blocks of life as we know it.

//JACK COHEN:// Carbon is a very useful element to sit at the center of life's chemistry. There's a lot of it in the universe. It's made very easily in stars. It makes very complicated, meshed-together compounds which have the possibility of changing each other's properties. You can have a really complicated, complex setup with carbon. I'd expect that very nearly all life forms we come across that are matter-based are going to be carbon-based.

//NEIL deGRASSE TYSON:// If carbon helps make life happen, then there might be a lot of life out there. Carbon is one of the most common elements in the universe. So if it's got carbon, what else does life need? Lots of oxygen in the air? Seventy-two degrees? We tend to think life belongs in a place that's, well, comfortable for us. But is that really true? In the last few years, we've been finding life practically everywhere on Earth, and not just the obvious spots. Microbes are thriving under rocks in the driest, hottest deserts. Life's doing just fine in the dark bottom of the oceans, warmed by deep sea vents. And now, life is turning up in some of the coldest, bleakest conditions imaginable, including the ice sheets of Antarctica and Greenland. So now that we've found life not just surviving, but thriving just about everywhere on Earth, suddenly it's looking more likely that life might thrive in lots of places beyond Earth, even if we would find them a bit uncomfortable. If life is common, then we should be able to find signs of it beyond our own little planet. Unfortunately, the evidence has been elusive. It's seems as if one crucial ingredient has been missing.

//CHRIS McKAY// (NASA Ames Research Center)//:// The most important requirement for life is liquid water, and that's the defining requirement for life in terms of our solar system. There's plenty of energy, there's plenty of carbon, there's plenty of other elements on all the planets in our solar system. What's rare, and which, as far as we know, only occurs now on Earth, is liquid water.

//NEIL deGRASSE TYSON:// Liquid water is crucial because it's an ideal solvent. Molecules can easily move around in it and react with one another, allowing the complex chemistry of life to do its thing. For years, it seemed that Earth, with its oceans of liquid water, was an oddball and perhaps the only, place in the solar system where life had ever thrived. Then we started to look more closely at our neighbors. In recent years, NASA spacecraft have sent back images of Mars with stunning detail, and there are clear signs of a watery past.

//CHRIS McKAY:// From orbit around Mars we can see ancient rivers that are now dry, canyons which look like they had lakes in the middle of them, even what looks like an ancient ocean floor in the northern hemisphere. We see unmistakable signs that Mars was a wet place.

//NEIL deGRASSE TYSON:// And now there's even more information from NASA's twin rovers that roamed the Red Planet, taking pictures and probing the rocks for their chemical makeup. The photos reveal clear sedimentary layers in the Martian rocks, and chemical analysis shows they must have been laid down in the presence of water. Mars might be too cold and dry to harbor life today, but if water was once there, then perhaps life was, too. And now, there's hope that life may thrive even farther out in the solar system.

//CHRIS McKAY:// I think Mars is the number one candidate for the search for life beyond the Earth, especially if we're going to find it soon. But we do have a backup plan, and in this case the back up plan is Europa, one of the moons of Jupiter. A little smaller than our moon, Europa is covered with ice, but there are cracks in its surface, perhaps signs of ice sheets floating on a deep ocean of liquid water. What might be melting the ice is internal friction created by the gravity of Jupiter and its other moons. Europa's ocean is suddenly considered a potential home for life.

//FRANK DRAKE:// The places where life can live and exist are far more extensive than we used to imagine. We used to think a life-bearing planet would be just like the Earth, and a little closer to the sun it would be too hot, a little farther away it would be too cold. And now we realize, "Oh, gosh, there's a place which has an ocean with three times as much water as the ocean of Earth, and the water is warm." And that's way out in the solar system where we used to think the temperatures were ridiculously low; there could never be life there. So the likelihood of life existing on planets in space has just gone up enormously.