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BBC The Planets Destiny

evolution of stars and one in particular ours The sun is the life-force of our solar system. The Earth is wholly dependent on its energy. Their fates are entwined forever. But in the future the sun will change. One day its benevolent influence will turn against the planets it has nurtured for so long. The astronauts who went to the Moon thought they would be the first in a long line of travelers in space. But in fact there have been no more. The last man to set foot on another world was Captain Gene Cernan. The Moon is bland, it's grey in shades. And other than the color you have brought here yourself, the only color you see out there is the Earth, multicolor blues of the oceans, and whites of the snow and the clouds. And the Earth itself is three-dimensional and it moves through this blackness with logic, with purpose and with beauty beyond comprehension. For the first time ever, you're beginning to see the Earth as a planet which you never saw that way before. It's spiritually different to be able to see the Earth evolve, see something that is very strange and yet very familiar, and it's something. I guess I didn't expect to see - it is as you head out to the Moon - which Earth grows smaller very, very quickly at first, until the point does come when you can literally block out all humanity, your identity with reality, with something no bigger than the size of your thumb. Since the Moon missions, nothing and no one has been far enough away to be able to capture a view of our planet from a greater distance... until Voyager. The unmanned Voyager spacecraft were launched in 1977. They are now leaving our solar system and heading for interstellar space. On their way, they have sent back photograph after photograph of the planets in beautiful detail. But there was one more picture that just had to be taken, a final gift from the probe's revelatory journey. The idea occurred to me that Voyager was gonna be in a location that no other spacecraft had been before, equipped with, you know, sophisticated instrumentation, so that it could turn around and take a picture of all the planets in the solar system. And I thought that this would be a riveting collection of images, you know, a first. Voyager scientist Carl Sagan had long campaigned for the spacecraft to be turned around. But the risk of sun damage to the cameras was seen as too great. At first, Carolyn Porco met with the same response. And they said, "Well, you know, there's really no scientific justification for this" and I couldn't argue with that because there wasn't. You know these, the planets were gonna be just pinpoints, they were gonna be just pixels. You know, they couldn't see it. But as Voyager came to the very end of its mission, there was nothing to lose, and on Valentine's Day 1990, 13 years after leaving Earth, Voyager turned its cameras back towards the now distant planets. The spacecraft was 3.7 billion miles away. Each signal took five and a half hours to reach the Earth. No single image could capture the entire solar system, and the mosaic of pictures stretched six metres across. The planets could barely be made out. Mars and Pluto were too small to be recorded, and Mercury was lost in the glare of the sun. And I took my hand, and swiped the glossy print, trying to remove the dust off it, ok? And it turned out that one of those specks of dust was the image of Earth, ok? It was that small. These were not tremendously beautiful, glorious images. I mean we knew they wouldn't be. That wasn't the point. The portrait of the planets that has now been taken, is, it seems to me, in the same tradition as the extraordinary color photographs of the whole Earth taken by the Apollo astronauts on their way to the Moon. This looks like more than a dot, but it is in fact less than a pixel. In this color picture you can see that it is slightly blue, and this is where we live - on a blue dot. I talk about standing on the Moon and looking at the Earth, and describing it as humanity, my identity with humanity. I mean think about moving outside of our solar system, and seeing it as Voyager saw it! But that's what we've now done. We came to know the solar system; we came to know its history. We came to know how it's configured, and we're starting to piece together how it possibly came about, basically because of the Voyager mission. The Voyager mission gave us a perspective on things that, you know, we just didn't have before. But what Voyager showed was just one moment in time - a snapshot. One thing we are certain will change is Saturn. In a hundred million years the rings won't be there any longer. They will be worn away by the bombardment of meteorites, little bit by little bit. That material basically gets lost to the Saturn system or else it ends up spiraling in and being consumed by Saturn. It means the whole solar system will be completely reconfigured. You wouldn't recognize it. In one billion years, at Neptune, the moon Triton will spiral inwards towards its planet, gradually encroaching, until the moon is ripped apart. Out of this destruction will come something even more spectacular. Close in to Neptune is a collection of satellites, and if you took those satellites in all and bashed them all up at the same time the material would spread out to form a ring system that would look pretty much like Saturn's rings. So we might, you know, while losing Saturn's rings, we might have, in the future, another beautiful supernatural-looking ring system around Neptune. Which wouldn’t be too bad a swap? Whatever the solar system will look like, the most important question is what will happen to the sun, the heart of it all? The sun's fate will determine ours, but how will it change? The answers lie in the moon rocks gathered by the Apollo astronauts. "You're just about full.”I got some small ones." "That's a big one." "Don't fill it too full." We took some of the rocks and brought them in the spacecraft with us, we would get out of our suits and we'd examine the rocks with our bare hands. The dust would literally penetrate into the pores of our skin and beneath our nails - I mean just way down in. It was like weeks and weeks before, when I got back, before that lunar dust ever grew out with my nails, was depenetrated, if you will, from my skin. For billions of years, constantly bombarded by solar particles, the Moon has been a diary of our sun. Its rocks act like a sponge, quietly absorbing the particles, and so keeping a record of the sun's activity. The Apollo astronauts removed the rocks buried beneath the lunar dust, and brought them home. The rocks show how the sun's energies have fluctuated over time. It has been much more active in the past. The sun is ageing, and we, too, are part of that ageing process. I think, thinking about the planets, and the sun and solar system as a family of objects, and wondering what their long-term future, I think is is a sobering process, because we tend to think of the Earth as... as forever. "The eternal sea," we call it. But yet when we start looking at the planets in the solar system, we realize they're not eternal, that the Earth is some sense halfway through its lifetime, its expected lifetime. We're living on a middle-aged planet. The Earth is middle-aged because the sun is middle-aged. As the sun gets older it will start to work against us. Since its creation, it has been getting 10% hotter every billion years. In just one billion years' time, it will become so hot that it will begin to destroy life on Earth. Plants and animals will find it hard to cope with the rapidly falling levels of carbon dioxide. Our time on Earth could be limited by these events. If we were to come back in our solar system in a billion years, it's still the place where you can find liquid water and go for a swim. Earth is still the planet of choice, I think, in a billion years. Maybe two billion years or three billion years, it's now starting to become a hothouse here. The oceans might start warming up and evaporating into the atmosphere, creating a runaway greenhouse, and the Earth would be like Venus, a very thick atmosphere trapping in a lot of heat.


  The Planets Destiny
 
The evolution of stars and on the destiny of one star in particular ours
The evolution of stars and on the destiny of one star in particular ours 		  All the planets will change and evolve in different ways before the end of their lifetime
All the planets will change and evolve in different ways before the end of their lifetime 		  There are 100 billion individual stars within our galaxy, and there are at least 50 billion galaxies in the universe
There are 100 billion individual stars within our galaxy, and there are at least 50 billion galaxies in the universe 		  Saturn's rings
Saturn's rings
 
And as the sun gets even brighter, the Earth might eventually just vaporize, so we can see the gradual steps and the Earth becoming less and less desirable as a place to live. There will reach a point where Earth is no longer habitable. So ultimately we have to find another place to live. It could go from being too cold to being too hot. Mars is probably not a long-term place for home, but if you think about that there's no place that's gonna be suitable forever. It's just a question of how long. How long do we wanna have the rent on this planet or that planet? Earth, we've been lucky, we've had several billion years. Mars, we may have half a billion years. But still a place to live for half a billion years is a good place. As the sun warms, the moons of the distant planets will perhaps be the best hope for life in the future solar system. Jupiter's moon Europa is already the most likely haven. Far below its dense and inhospitable layers of ice, some form of primitive life may even now exist. Dr David Black is chairman of the NASA Origins program, a program designed to search for the signs of life in the space. The moon Europa is very, very intriguing. It appears it's an ice-covered planet, but of the features that we see on the surface suggest that in fact there's a liquid ocean below that. How extensive, we don't know yet. That's one of the things we will try and explore in the future. We know that deep down in our own ocean, where there's no sunlight to speak of, we've seen signs of life near these deep sea vents, the "smokers" as they're called. But the future of planet hunting will lie not in ground-based observations but in space missions. 200 miles above us, the Hubble Space Telescope is the first witness to the exotic nature of the cosmos. Probably the most important telescope in the line of telescopes that we're thinking about for the Origins program is a device that we call the Planet finder. This is a very large telescope that will probably be what scientists call an interferometer. It's really more than one telescope. It'll be made up of four or five small telescopes that will mimic a very large telescope.
Telescopes like Planet finder will allow us to see extra solar planets for the first time, bringing the unimaginable into sharp focus. The Planet finder will provide us not with a picture in the sense we're used to seeing from satellites in orbit around the Earth. We won't get that kind of a picture. What we will get is...a dot, is about all we'll get in terms of the image, but the signal that comes from that dot will be the key thing for the scientists. But what can a dot of light tell us about another planet, far away in the universe? Before the probe Galileo headed for Jupiter it looked down at Earth to see if life could be detected from space. What Galileo showed us was that in fact these molecular signatures that we think are indicative of life on a planet were really there, and you could separate them out so it gave us some confidence that by looking for similar signatures when we look at the atmospheres of other planets, that we could maybe infer from those signatures that life was there as well. The signs of life as we know it are universal. The combinations of chemicals on Earth could be repeated on any planet in space, and all of these chemicals are now identifiable from a distance. And we'll be looking for things like signs of water in the atmosphere, carbon dioxide - which will indicate that it's got a substantial atmosphere, ozone which says that there's oxygen in the atmosphere. And all these taken together each one tells you something about the likelihood that the planet is either inhabited or may be habitable. If you can find methane, especially with oxygen in the atmosphere, it's a slam-dunk, as we say in America in basketball, that you can conclude that life is on that planet. And in the right place in a solar system, many now believe that the combination of these elements will almost certainly mean life. If you hand a biochemist a planet with a rocky surface, with a temperature that's not too cold, so that water is frozen into ice, and not so hot that the water is evaporated into steam, but, in the words of Goldilocks, is "just right" for the liquid form of water. It will pool into lakes and rivers and streams and, of course, oceans, and the biochemists are unanimous that the laws of chemistry will take over. You'll end up with complicated organic molecules that we, in fact, would call life. But we've yet to find a planet that falls within this "Goldilocks" zone, and is rocky and small enough to be suitable for life, like the Earth. I would be happy to find an Earth-like planet, even cold, or far away, or close by, or too hot, or anything, I'd like to see that these exist, because if I find one of those, I'd be sure there are others elsewhere that might be more suitable for life. So I think that the major question is to see one, and then we'll start being picky, wanting them at the right temperature. Like Voyager looking back at our family of planets, telescopes in space may one day allow us to look at distant worlds. The Earth is very insignificant at least in a cosmic sense. Very significant to us. But in the cosmic sense it's that pale blue dot as Carl Sagan said often; off in the distance and in many ways much of what the Origins program is about is the search for another example of a pale blue dot. Some 500 years ago Copernicus, in effect, removed the Earth from the centre of the universe. We have since had great observations that showed that the sun itself is nothing special, neither is our galaxy. But the thing that remains is that we only have evidence for one example of life, and that's the life that's on this planet. We are so obsessed with finding other life forms, and understanding how life originated. It's like life needs to seek out itself. That's manifest in our thinking. Almost certainly, any expedition we mount to another solar system will be to a solar system that looks like it's going to be most like our own. It's not beyond the stretch of imagination to think of sending a probe, an automated probe. Imagine that you're sitting at a control room, 50 or 60 years in the future after this probe is launched, and suddenly this signal comes back, and you're not quite sure what it is and you scratch the computer archives - and by the way this probe is actually one we sent to Beta Hydra - 50 years ago and now it's telling us what that remarkable place is like. I think that would be very exciting. It was curiosity about what lay beyond our atmosphere that drove us into space.