Introduction

In this first episode of our brand new series, Beyond Earth, we’re going to start our journey exploring our own solar system before we go further and deeper in our journey into the universe.

Audio Episode

Episode Transcript

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The Chinese say that a journey of 1000 miles begins with a single step. It is fitting then that we begin our exploration of the universe in our own astronomical backyard, our own solar system. That’s our very first episode in our brand new series beyond Earth. We’re going to talk in today’s episode about the solar system. I’m going to introduce you to the planets of the solar system. And we’ll talk a little bit more. I’m so excited about this new series. Because after we talk about the solar system, the Milky Way in the universe, we’re going to start to tackle some space mysteries, such as the big question, are we alone? And a lot of interesting questions. But first, as I said, the journey of 1000 miles or not, as I said, as the Chinese said, the journey of 1000 miles begins with a single step. And our very first step for today’s episode is going to be in our own solar system. This is your host, Danny and this is a new episode from English plus podcast. Now before we start, let me remind you that you can find the transcript of this episode on my website, English plus podcast.com. The link is right in the show notes. So just click on it when you’re done or right now if you want to follow along, and I have to remind you as well that yesterday, we started English plus premium one premium episode to match every free episode we have in our podcast, and these premium episodes are available only to my Patrons on Patreon, you can find the link to my Patreon page in the show notes, take the link, become a patron and enjoy all the premium episodes and a lot of other benefits that are coming your way if you become a patron. And now let’s not waste any more time and let’s start talking about the very first episode in our exciting new series beyond Earth. And we’re going to talk about the solar system in our very first episode.

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every planet in our system has been visited by one or more spacecraft, some of them actually landing on the planet. We have explored not only the planets, but also their moons. And we have come to realize that every world in our system has its own unique story to tell. Modern research has extended our idea of the limits of the solar system. Even beyond the orbit of Pluto and the Kuiper Belt and Oort cloud planet size worlds have been discovered out there as well as countless smaller objects. And we are now seeing the inner planets as just a small part of the entire system. The well publicized demotion of Pluto is an example of this new perspective. So before we start talking about the planets and their moons, let’s start talking about the formation the birth of our solar system. It all started 4.5 billion years ago with an interstellar cloud. The explanation of what happened began with French physicist Pierre Simon Laplace, who theorized that the ordinary laws of gravity would produce something like our solar system from this interstellar cloud. Laplace reasoned that there would naturally have been random regions in the clouds where mass was more concentrated, they would have exerted a stronger gravitational force pulling in surrounding material. Eventually, one of these concentrations became our own solar system. Most of the mass of the pre solar nebula became concentrated at the center in the sun, the remaining material flattered into a rotating disc. out to a distance between the present orbits of Mars and Jupiter the temperature was hot enough that volatile materials like water and methane couldn’t exist in solid form. Beyond this boundary, which astronomers referred to loosely as the frost line. These materials remained as solid ices and so the building blocks available for the inner planets were different from those available for planets beyond the frost line. So what about the terrestrial planets the inner planets formed primarily from materials with high melting points like iron and nickel, grains of these materials collided and stuck together, forming bodies cold planetesimals, it is these bodies that eventually came together to form the planets. The end results of this process was an inner solar system with dozens of Moon sized planetary embryos zipping around. What followed was a frenetic game of planetary billiards, after which the inner solar system was left with four terrestrial planets that we see today. What about the giant planets? Meanwhile, the bodies beyond the frog Last line began capturing the abundant hydrogen and helium surrounding them. And by doing that they were growing massive. These planets are known as gas giants and they are the largest planets in our system. about 4 billion years ago, Jupiter and Saturn pushed Neptune’s orbit outward moving Jupiter closer to the sun. Jupiter’s shift affected the asteroid belt, leaving it in its present condition. Once these initial fireworks died down, the solar system became a much more orderly and predictable kind of place. Over the last few decades, it has become clear to astronomers that the formation of the solar system was far from a placid orderly collapse, but was a wild chaotic process, tope that was about the beginning. That was the birth of the solar system. But that’s just the beginning of our episode, of course, we’re going to start talking about the planets, the juicy stuff, and our very first planet is the closest to the sun. And here we’re going to talk about Mercury. Of course, that’s coming next. Don’t go anywhere. I’ll be right back.

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Mercury is the closest planet to the sun and always appears as a morning or evening star to observers. Records of naked eye sightings of mercury go back to 14th century BCE, Assyrian astronomers, and by the fourth century BCE, the Greeks had realized that these morning and evening stars were actually a single body. So let’s talk more about Mercury itself. Mercury is small, and it has long since lost whatever atmosphere it ever had. It is a dead world. And its main features are craters from long ago impacts. As you might expect, for a planet so close to the Sun, Mercury surface temperatures can get quite hot, up to 427 degrees Celsius, that’s about 801 Fahrenheit. And that’s like the temperature at the equator at high noon. Well, that is predictable, because obviously it is the closest to the sun, it is supposed to be the hottest planet. But think again, you’re gonna discover other things in this series that you might not have expected before. But anyway, let’s stick to Mercury now. And the thing that you might not expect that it can get quite cold as well. While actually at midnight, it gets to a minus 173 degrees Celsius, that’s minus 279 degrees Fahrenheit. Interesting, isn’t it? So that is the hot and cold mercury. But as I told you, it’s a cratered world. Because the planet has no atmosphere, craters on Mercury last for a long time. The largest of these, the Caloris basin must be the scar of a very large impact. In fact, on the exact opposite side of the planet is a region of jumbled hills that some scientists think was created by a shockwave from the impact that created to Loris Mercury has a small magnetic field and an unusually large iron core comprising over 42% of its volume. Several theories have been advanced to explain this unusual composition. The most popular explanation is that Mercury was struck by a large planet is small, about 4 billion years ago, the collision blew off a lot of the lighter outer layer of the planet, leaving behind the iron in the core. But remember, that’s only a theory. So that was about Mercury, the Swift Sun blasted world. What about the missions to Mercury because it is so close to the sun. Observing Mercury with ground based telescope is so difficult. Most of our information about the planet structure comes from two space probes. The first of these Mariner 10 arrived at the planet in 1974. The MESSENGER spacecraft made its first fly by of mercury in 2008, and went into orbit around the planet in 2011. And NASA’s MESSENGER spacecraft is still in orbit around Mercury sending back data. It completed its 2000s orbit around the planet in May 2013. So that was about mercury, our very first planet in our solar system. And of course not the last next you know what comes next right? It’s Venus. That’s the second closest planet to our sun. That’s coming next. Don’t

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go anywhere. I’ll be right back. Now the name Venus of course implies a beautiful planet, right? Well, it is obviously a beautiful Inferno. That’s what Venus is all about. Well, not the real Venus or actually the mythological Venus. But this planet is a beautiful Inferno. It is often called Earth sister planet. We in his ways in about 85% of Earth mass, like Mercury, Venus is seen only as a morning or evening star. And aside from the moon, it is the brightest object in the night sky. The Romans named the planet after they are goddess of love. So now let’s talk about some details about this beautiful planet. Venus completes an orbit around the sun in about 225 days. Curiously, it rotates backward. scientists suggest that this anomaly is the result of a collision during the violent early days of planetary formation. A thick layer of white clouds perpetually obscures the surface of the planet. Under those clouds, Venus is extremely hot, around 462 degrees Celsius, or about 864 degrees Fahrenheit, which is hotter than the surface of Mercury, despite Venus’s greater distance from the Sun. And mostly scientists believe that this is the case because of the very thick atmosphere it has, so it traps more heat inside while Mercury technically has no atmosphere at all. So let’s talk about the missions to Venus in 1970. The Soviet spacecraft veneer oh seven made it to the Venusian surface and sent back pictures. This was followed by several more spacecraft that landed successfully. In 1978. The American pioneer Venus mission produced the first detailed maps of Venus radar mapping reveals of a newseum surface shaped primarily by volcanic activity. About 80% of the surface consists of smooth planes with two high land continents making up the rest 167 volcanoes on the Volusia and surface are bigger than the one forming the big island in Hawaii, which is the largest volcano on Earth. There is evidence that many Volusia and volcanoes are still active. That’s why we called it a beautiful Inferno. And Venus doesn’t have oceans so without oceans to observe it, the concentration of carbon dioxide grew as the volcano spewed out, the planet experienced a runaway greenhouse effect that produced the intense temperatures we see today. Venus’s atmosphere is now almost pure carbon dioxide over 95% of it is carbon dioxide with most of the rest being nitrogen atmospheric pressure at the surface is 92 times then at sea level on Earth. Venus clouds are composed mainly of sulfur dioxide and sulfuric acid. It drains sulfuric acid on Venus, but the drops evaporate as they fall through the thick atmosphere. Intense winds at high altitudes have speeds reaching several 100 kilometers an hour. We do not understand yet what causes these, the planes are dotted with impact craters, most of which show no evidence of weathering. Scientists argue that this fact implies that about 500 million years ago, Venus underwent a resurfacing event during which lava flows covered the old surface with its craters creating the smooth planes we see now and presenting a new surface for incoming meteorites. So definitely a beautiful planet. But it’s a beautiful infernal planet where life as we know it is impossible. So that was about the second planet in our solar system. What about the third? Well, you know, the third, it’s actually the most important and most famous planet in the solar system ever. And here I’m talking about our own planet Earth. That’s coming next. Don’t go anywhere. We’re going to talk about Earth next.

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So don’t go anywhere. I’ll be right back. So why is the earth different? There are actually two important distinctions our planet has. First, it is the largest terrestrial planet which is related to the fact that its surface is constantly changing. And second, Earth’s orbit lies in a narrow band around the Sun known as the continuously habitable zone, which is defined as the region in which liquid water can stay on the planetary surface for long periods of time. Because of this Earth is the only object in the solar system where we know life exists. Keeping liquid water on the surface requires a delicate balance between the development of the sun and changes on Earth. When the solar system first formed, the Sun gave out about 30% less energy than it does today. As the sun grew brighter changes were occurring on earth that compensated for the increased radiation. The most important of these changes was the appearance of life primarily blue green algae in the oceans. Through the process of photosynthesis, these algae began adding oxygen to the atmosphere with changed the atmospheric chemical composition. The ability of the planet to trap heat from the faint young sun and keep water liquid began to wane. And some scientists argue that the Earth narrowly missed becoming frozen solid at this point in its history. For the first half billion years of its existence, Earth’s swept around its orbit collecting debris from the process of planetary formation. Had you been standing on the surface then you would have seen impact after fiery impact of large meteorites all around you. Scientists refer to this period as the great bombardment. Each impact added a certain amount of energy to the newly forming planet energy that was converted to heat. Eventually, Earth melted all the way through, or at least heated up to the point that it became soft enough for matter to flow easily. The heaviest materials mainly iron sank to the center to form Earth’s core. While lighter materials formed the mantle and crust, like salad dressing left untouched to long the Earth’s components separated themselves out under the influence of gravity. In addition, the motion of molten materials deep within the planet had the effect of moving continents around in a continual dance. 500 million years ago, for example, all the continents were strung around the equator like pearls on a necklace between 300 and 200 million years ago, they were all clumped together in a single mass called Pangea, which means all Earth and as continents move, the surface of the planet changes. The Himalaya, for example, were created when the Indian subcontinent collided with the Eurasian landmass. And the Urals are the scar created when Europe and Asia joined together. So that was about the Earth and how it formed and how we live in it. Of course, there’s

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a lot to talk about Earth. And I will tell you something that I am not supposed to tell you now, because that’s something for the future, we are going to have an entire series that talks only about Earth, and it will only include information that will blow your mind. But let’s just keep that in the back of our minds, because that’s not going to happen. Now. It’s going to happen in the near future. But anyway, let’s get back to our Earth and let’s talk about the moon. But we know we just have this one moon that we call the moon because obviously we have the advantage of cooling our moon of the moon. All right. So what about the moon? Well, obviously we know that the moon, as we all know is his world children. It is the brightest object in the night sky. There is a long history of scientific studies of the moon. In 1609, Galileo used the new telescope to produce drawings of the lunar surface showing mountains, planes and craters. The Far Side of the Moon, which is never visible from Earth was first photographed by the Soviet probe lunar three in 1959. The Space Race fueled by the cold war resulted in the first human being setting foot on the moon in 1969, when astronaut Neil Armstrong uttered his famous line, That’s one small step for a man one giant leap for mankind. Since the end of the Apollo program in 1972, only unmanned probes have gone to the moon. We now know that the moon like Earth was formed about 4.5 billion years ago, but scientists have always debated how this happened. The basic Enigma is that the moon is significantly less dense than Earth primarily because the moon has such a small iron core, how could Earth and the Moon both of which apparently formed in the same part of the planetary cloud end up looking so different? The currently favored theory is that early in the formation of Earth, but after its iron had gravitated to the core Earth, and a similar Mars sized objects collided, this collision broke off large chunks of both planets lower density mentals and some of this ejected material went into orbit around Earth. At this point, the same process of accretion that built the terrestrial planet came into play and the Moon formed from that orbiting material. The main features on the moon’s near side or the side that is visible from Earth are the large dark planes called Mario or C’s that cover about a third of its surface. The far side does not have many of these features, these planes are actually massive outflows of lava. The lighter areas on the moon, usually referred to as high lands are older, perhaps 4.4 billion years old, and they represent the first materials to crystallize from molten material as the moon cooled. the Mauryan high lands together produce the familiar Man in the Moon image that you can see whenever the moon is full craters. The result of meteorite impacts over the eons dot the lunar surface Since the moon has no atmosphere to speak of, and since it is now a frozen world with no geological activity, there is nothing to remove these craters once they form and as a consequence, there are hundreds of 1000s of them visible on the moon today. So that was about our Earth and the Moon. And next, you know, what are we going to talk about? We’re going to talk about maybe the most famous planet after our own Earth, of course, we’re going to talk about the red desert, we’re going to talk about Mars that’s coming next.

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Don’t go anywhere, I’ll be right back. Mars is the most thoroughly explored of all the planets except earth of course, and has probably figured in more science fiction than any other astronomical object. Named from the Roman god of war, Mars often appears to have a reddish cast and lost most of its atmosphere to space long time ago, the axis of rotation for Mars is tilted at approximately the same angle as that of Earth. So the red planet has seasons just as we do. It’s here is about twice as long as ours however, so each of its seasons lasts twice as long as those on earth during the Martian winter on each hemisphere, no sunlight reaches the pole and large amounts of carbon dioxide freeze to produce a thick layer of dry ice. Under this layer is a large, permanent polar cap of water ice. current theories suggest that both hemispheres are covered by oceans early in Marcis history do remarkable features on the Martian surface deserve special attention. Olympus Mons, which is an extinct volcano is the largest mountain yet discovered in the solar system with a height of 27 kilometers that’s about 17 miles, it’s over three times as tall as Mount Everest. At the other extreme valus marine Eris is a canyon system about 4000 kilometers or 2500 miles long and up to seven kilometers or 4.5 miles deep. Or by comparison, the Grand Canyon in Arizona is about 800 kilometers, or about 500 miles long and up to 1.6 kilometers or one mile deep. In 1877, Italian astronomer Giovanni Schiaparelli surveying the Martian surface with a telescope saw lines that he called Canakkale, or channels. Unfortunately, this was translated as canals in English, which suggested the presence of intelligent life on the planet. American astronomer Percival Lowell brought the concept of an inhabited Mars to the attention of the general public. The theory promulgated at the time was that Mars was the home of a dying civilization. We now know that lolz canals were optical illusions, and his conclusions were based on the well known tendency of humans to see patterns in random assortments of images. So unfortunately, we don’t have a clue. I’m not saying not exactly mean, not even scientists, they’re not saying that it was impossible or it is impossible for life to exist or to have existed on Mars, but we have no proof of that whatsoever. And the canals were just optical illusion. So that was about the planet itself. Well, what about the missions to Mars? The modern exploration of Mars started when Mariner four flew by the planet in 1964, and gained detail in 1971 when Mariner nine went into orbit. The biggest surprise the spacecraft produced for scientists was photographs of gullies that looked like ordinary river watersheds on Earth. The biggest Martian event for the general public, though, was the landing of the Viking one and two spacecraft in 1976. Then in 1997, the first robotic vehicle Sojourner dropped to the Martian ground. This was the first successful landing of a rover on another planet, and it pioneered the technique of surrounding the rover with airbags to cushion the landing, then deflating the airbags to allow the vehicle to move. The 21st century has seen a veritable flotilla of spacecraft landers and orbiters launched toward the red planet. The most dramatic missions were those of the Mars Exploration Rovers Spirit and Opportunity, which landed successfully in 2004. These rovers examined Martian rocks and minerals establishing in short order that liquid water once existed on the Martian surface. And now before we move to the asteroid belt, let me tell you about this curiosity marvelous rover. The successful landing of the Curiosity rover in August 2012 was a technological marvel. It employed first rockets than a parachute and finally a rocket powered sky crane to produce a soft landing. Curiosity is a Volkswagen sighs V Do you call that carry scientific instruments from six different countries, and its main mission is to look for organic molecules to determine whether Mars is now or ever was host to microbial life. That’s just exciting, isn’t it? And we don’t know what the future is holding for us. Now I know what some people say about space exploration that it is a waste of money. It’s a waste of time. But this is who we are. This is why we’re different from all other species on our planet, we always ask this big question, are we alone, not for other animals. Of course, they search for each other in the wilderness. But once they kind of mark their own territories, they don’t care to roam the world searching for other animals that look just like them. They don’t seem to care, or at least most animals don’t seem to care. But we do. We want to know, we need to know if there are other animals in this big universe that are just like us. And I know that some people are skeptic about the whole thing and the whole lunar landing and stuff. And Neil Armstrong never made it to the moon. I know what some people said. But this is obviously not about conspiracy theories. Here. We’re just talking about facts. We’re talking about something that I believe is so exciting, something that keeps us looking into the night sky and marvel at things that look so close, but they’re actually so far away out of our reach for now, who knows, maybe we will figure out some way to get there in the future. But anyway, we talked about Mars we talked about the first four planets are the inner planets that are closest to the sun. Next we’re going to talk about the asteroid belt before we talk about the Giants. So next asteroid belt is coming. Don’t go anywhere. I’ll be right back.

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Dividing the terrestrial and Jovian planets in our solar system is a thin ring of debris known as the asteroid belt. Despite the crowded rock strewn scenes you may have witnessed in the movies, the asteroid belt is almost completely empty. The first asteroid series was discovered in 1801 series has the largest body in the asteroid belt at about 950 kilometers or 590 miles across, and is now classified as a dwarf planet. Everything else in the belt is smaller and irregular in shape. It is estimated that there are around 200 asteroids more than 100 kilometers or 60 miles across, and perhaps over a million larger than one kilometer, or 0.6 miles. Some asteroids travel in path that bring them inside the orbits of Mars and Earth, which raises the possibility that they might collide with either planet. So let’s talk about how the belt took shape. When the solar system was forming the process of planetesimal accumulation went on in the asteroid belt as well. One theory postulates that the gravitational pull of Jupiter was able to prevent a planet from forming, studying these ancient bodies should cast some light on the way the solar system formed. But we still don’t know for sure, of course, and you might have guessed by now that most of the information we have here, except for some that we know for sure, but we have a lot of theories because we can’t even go there. I mean, these places are very close to us comparatively to this big universe, or even the Milky Way that is our own galaxy. These places are very close, but they’re very difficult to get to. But anyway, talking about getting to these places, let’s talk about missions to the asteroid are beginning in 1972, a number of spacecraft the pioneers, the voyagers, and Ulysses passed through the Asteroid Belt without mishap, but none of them tried to image the asteroids they passed. The first that did was the NIR probe or the N E A R probe, which means near Earth asteroid rendezvous, it went into orbit around the Near Earth asteroid Eros. In 2002 1010. The Japanese probe Hayabusa returned to Earth after a seven year 5 billion kilometer or 3 billion mile landing mission to a small asteroid named Itokawa. Although the spacecraft burned up on entry into Earth’s atmosphere, the sample return packet containing small particles of the asteroid landed safely in Australia. analysis showed that the asteroid indeed data to the early days of the solar system, NASA’s Dawn spacecraft launched in 2007, went into orbit around the massive asteroid Vesta in 2011. And after Vesta, it’s moving to series and its mission is to study each of these bodies in some detail with the hopes of learning more about the formation of the solar system. So that was about the asteroid belt. And next of course, we’re going to talk about the giant, the biggest the king of the gas giants Jupiter, so don’t go anywhere. You don’t want to miss that.

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I’ll be right back. Jupiter is the largest planet backing over two and a half times the mass of all the other planets combined. As seen through a telescope. It is a beautiful thing with alternating stripes of different colors and surrounded by a swarm of small moons. Jupiter’s atmosphere increases in density as the surroundings change from gas to liquid to slush. We wouldn’t encounter anything we could call a solid surface until perhaps we got near the very center. Now surrounding Jupiter’s rocky core is a layer of a strange material called metallic hydrogen. pressures in the interior of Jupiter are so high that the atoms of hydrogen gas are forced into a state that has the properties of a solid metal. metallic hydrogen, which is an exotic rarity on Earth makes up a significant fraction of the mass of Jupiter, the layer of metallic hydrogen is covered by a layer of ordinary liquid hydrogen. And after that, we have those belts and zones, and Jupiter’s fast rotation produces many counter rotating bands in the atmosphere. These become the beautiful colored stripes we see when we look at the planet due to a rather complex cloud structure in the top 50 kilometers or 30 miles, the outermost layer of the planet is composed almost entirely of hydrogen and helium. The colorful bands result from upwelling materials that change color when they encounter the ultraviolet rays of the sun producing dark bands or belts that we can see. The lighter bands or zones are clouds of crystallized ammonia carried upward. Perhaps the most striking feature on Jupiter is the Great Red Spot, which is a storm in the southern hemisphere, it is so big that the entire Earth could be dropped into it with room to spare. Now, of course, this great spot, which is believed to be a great storm has been raging for over 400 years. And we know that because it was first observed over 400 years ago, but some even wonder has the Great Red Spot always been on Jupiter. Maybe the storm is quite older than that. Who knows. But now let’s talk about Jupiter missions. Many spacecraft have flown by Jupiter on their way to other destinations. The Voyager spacecraft in 1979, I discovered that Jupiter has a system of rings. The main space probe associated with Jupiter was the Galileo mission inserted into orbit around the planet in 1995. For seven years, the orbiting Galileo spacecraft gathered a trove of data on Jupiter and its moons. And now that we’ve talked about Jupiter, kind of talk about Jupiter’s moons and how we were bragging about the moon that we have, but Jupiter actually had 65 moons, so we’re just kind of like dwarfs next to Jupiter. But anyway, we are actually because our planet is much smaller than Jupiter. So Jupiter has 65 moons, most are irregular lumps, some only a few kilometers across, and only a few fit the standard image of what a moon should be. Each of these is unique. Each has its own story to tell, and we can talk about every one of them. But of course, because there is not enough time to talk about those 65 moves, we’re gonna focus on only two of them Io and Europa. Let’s start with IO. Now IO is the inner most of the Galilean moons, it’s slightly larger than Earth’s moon, and it’s the fourth largest moon in the solar system, it’s molted surface is the result of more than 400 active volcanoes injecting various sulfur compounds, which are the chemicals that give it its orange and yellow colors. These volcanoes make IO, the most geologically active body known because of the gravitational pull of the other moons, the distance of IO from Jupiter is always changing so that the gravitational force on the moon changes as well. This means that IO is constantly being flexed and distorted. So the moon gets warm, just as a piece of metal that is bent back and forth will heat up. We see the result of this so called tidal heating in AIOs extensive volcanoes. So that was IO. What about Europa? And at first glance, there doesn’t seem to be much about Europa to command our attention. It is slightly smaller than Earth’s moon. Europa has a smooth icy surface criss crossed by dark streaks. The most important thing about this moon is the fact that it has an ocean of liquid water under the thick layer of ice that composes its surface. calculations show that there is enough heat generated by tidal heating to keep a subsurface layer of water from freezing despite the fact that the temperature can be as low as minus 220 degrees Celsius or 306. to four degrees Fahrenheit at the surface, the current theory is that beneath a layer of ice, some 10s of kilometers thick is an ocean containing up to twice as much water as in the oceans of our own planet. Dope.

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That’s what’s interesting about Europa. That’s why we talked about it and about I of course, and actually recent calculations indicate that there might be processes by which the collision of particles with the Europen surface would introduce oxygen into the oceans. Now this raises the possibility of more complex life, perhaps even something like our own fish. Who knows this might be possible, but enough about Jupiter and its moons. Let’s talk next about Saturn and its moons that’s coming next. Don’t go anywhere, I’ll be right back. Saturn is a gas giant similar in structure to Jupiter. In appearance. Saturn is a little bland compared to Jupiter, although it has the same if less colorful, bandit cloud structure. The cloud we see appear to consist of water ice, ammonia compounds and ammonia crystals found in successive tears 10s of kilometers thick Satan’s winds are striking feature of its atmosphere registering at up to 1800 kilometers an hour or 1120 miles per hour, and these are definitely the fastest wins anywhere in the solar system. Satan has a large and powerful magnetic field and has auroras at both poles. So what about missions to Seder the Cassini spacecraft launched in 1997, entered orbit around Saturn in 2004. Most of the detailed information we have about the planet, its rings and its moves comes from this mission, which is still in orbit and returning data. Satan has a large array of satellites, but two moons that have attracted the most scientific attention are Titan and Enceladus. So let’s start with Titan. Titan is larger than Mercury and is the only moon in the solar system to have a significant atmosphere. It is also the one world in the system where we can perhaps get a glimpse of the kind of chemistry that led to life on Earth. Titan’s atmosphere is mostly nitrogen and support several cloud layers that make it impossible to see the surface from outside. And so a few months after its arrival at Satan, Cassini dropped a probe into Titan’s atmosphere which sent back the first images of the surface as one researcher put it. What was alien about Titan was its earIy familiarity, you can put the similarity of Titan to Earth in perspective by remembering that Titan is really cold and at these temperatures, materials can take an unexpected forms. In essence, what we see on Titan are familiar processes involving unfamiliar materials. For example, Titans high clouds are made of hydrocarbon molecules like methane and ethane rather than water. They interact with ultraviolet light from the Sun to produce a haze and the hydrocarbons collect on the surface, producing a kind of sand that drifts into Dunes. liquid methane condenses and falls out of Titan sky as rain to produce lakes and other familiar landscape features just as water does on Earth. That was about Titan. What about Enceladus? It’s the sixth largest moon of Seder Enceladus long was known to have a surface made of water ice. In 2005, Cassini recorded a geyser spewing out liquid water near the moon’s south pole, Enceladus appears to be heated by the flexing in Satan’s gravitational field. And so Enceladus may join Europa as a possible abode of life in our solar system. But of course, that’s not over.

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When we talk about Satan, we have to talk about Satan’s rings, those unique and beautiful rings surrounding the planet. The hoops of glittering ice, or the rings of Satan, which are the most spectacular objects in the solar system are made up primarily of chunks of water ice in orbit around the planet. Although today we know that all of the giant planets have ring systems, the rings of Saturn remain the most dramatic set. We have learned that the pieces of ice that formed the rings range in size from bits a fraction of a centimeter wide to boulders several meters across. The most astonishing thing is that in spite of their optical prominence, the rings are actually quite thin. Estimates put the average thickness of the rings at about 10 meters or 33 feet. An ordinary two storey building would barely stretch from top to bottom, so there are rings in ringlets and gaps in 1675. Italian astronomer Giovanni Cassini found that Satan’s rings were not a single unbroken hoop as they appeared in the earliest telescopes, but he had to dark gaps in the rings, dividing the rings into three parts. These parts were named the A, B and C rings, and the larger of these gaps is now called the Cassini division. The naming of rings discovered later took the alphabet up to G, with some also named for the moons that most influenced them. We now understand that the rings are actually complex structures with 1000s of thing gaps separating ringlets, the gaps seem to be maintained by a variety of gravitational interactions with Saturn’s moons. Now finally, we can turn to the question of how such a ring system might form. Now the most popular theory is that the particles are debris remaining from an ancient moon. Different versions of the theory have the moon breaking up because it got too close to Satan or because of a collision. What really happened, we don’t know. But anyway, it’s still one of the most beautiful things to witness in our own solar system. But we’re not done with our solar system yet. We still have Uranus and Neptune in the far reaches of the solar system, which we’re going to talk about next. So don’t go anywhere. I’ll be right back.

41:08
The last two planets in the solar system are the least known and the least explored. Uranus and Neptune formed closer to the Sun than their present orbits, and although they are similar to each other, they differ significantly from the gas giants Jupiter and Saturn. The atmospheres of Uranus and Neptune contain a lot more of the substances, astronomers call ISIS dense mixtures of water, ammonia and methane, and so they are often referred to as ice giants. ice giants are intermediate in size between the terrestrial planets and the gas giants. Neptune, for example, has 17 times the mass of Earth, but only 1/19 the mass of Jupiter Each has an atmosphere consisting of hydrogen, helium and methane gases add gets denser and denser as you descend. At some point, there’s a transition without a clearly defined surface to a hot liquid composed of the same materials at the very center of each planet is a small rocky core roughly the size of Earth. Like all the giant planets both Uranus and Neptune have multiple moons and ring systems. The German born amateur British astronomer William Herschel discovered Uranus with a telescope in Bath England. At first he thought it might be a comment. But as data accumulated on the new object, it became clear that Herschel had become the first human being in recorded history to discover a new planet. Much of our modern information about the planet was garnered when the Voyager two spacecraft flew by Uranus in 1986. The property that particularly catches our attention is the planet’s axis of rotation. It lies in the same plane as its orbit at 98 degrees, meaning that the planet is rotating on its side. Uranus has 27 moons named after such Shakespearean characters as Ariel and Miranda, and 13 narrow rings, and if the discovery of Uranus depended on a bit of observational serendipity, Neptune’s discovery was the result of careful calculation. As the newly discovered Uranus was trapped around its orbit. discrepancy started to appear between what was observed and what the law of gravity predicted. Two young astronomers John couch Adams in England and urban living area in France independently asked themselves whether these discrepancies could be due to the gravitational tug of another unseen planet still farther from the Sun. Following a series of complex maneuvers and communications astronomers at the Berlin observatory train their telescopes on the place where the unknown planet was predicted to be on September the 23rd 1846. The planet we now called Neptune was seen and recorded by Johann Gaal the tilt of Neptune’s axis of rotation is similar to that of Earth. So unlike Uranus, it has seasons and weather visited by Voyager two in 1989, Neptune was revealed to have large storms on its surface called the Great Dark Spot, the small dark spot and incongruously scooter These storms are similar in appearance to Jupiter’s Great Red Spot, but they seem to last for only months rather than centuries. Neptune is home to the strongest sustained winds in the solar system 2100 kilometers an hour, which is about 1300 miles per hour. Like all the giant planets Neptune has a large number of moves. The 13 of them are known so far, but one of them stands out from the others and it is called Triton. Triton is a large body larger than Pluto, for example. It’s big enough to be pulled into a spherical shape by its own gravity. What is interesting about it Is that alone among the solar systems large moons, it moves around Neptune in the opposite direction from the planets rotation. This suggests that the moon did not form at the same time as the planet, but rather that it took shape elsewhere and was captured. In fact, current thinking is that like Pluto, Triton is actually an object that formed in the quipper belt. It is believed to have a rocky core covered by a layer of frozen nitrogen. And it is one of the coldest objects in the solar system with a temperature only about 40 degrees above absolute zero. So that was about Uranus and Neptune. But these are not the last ones, we still have the outer reaches of our solar system that’s coming next. So don’t go anywhere. I’ll be right back.

45:51
Now here when we talk about the outer reaches of the solar system, we’re talking about Pluto, the Kuiper belt and the Oort cloud. Now, one time, Pluto was considered a planet an actual planet in our solar system. But today, however, we understand that the planets are just the beginning, and that the actual solar system extends far out into space farther than we ever imagined. So Pluto, remember Pluto, it is used to be a planet, right? But there were always problems with Pluto’s planetary status. For one thing, the plane of its orbit was tilted with respect to the orbits of the other planets. For another. The orbit was more elliptical than circular from 1977 to 1999. For example, Pluto was actually closer to the Sun than Neptune. And when the discovery of Pluto’s Moon K Ron in 1978 allowed astronomers to calculate Pluto’s mass a turned out to be smaller than our own moon here just a quick fact that in addition to Chiron, Pluto is now known to have four tiny satellites Nix, Hydra, Kerberos and Styx. So what about Pluto’s gravity? Now if you weigh 100 pounds on Earth, you would weighed eight pounds on Pluto, instead of the gas giant that our theories led us to expect out there. We had found a small rocky icy world, theorists began to believe that the solar system didn’t end with Pluto but extended outward in a ring of rocky debris called the Kuiper Belt. In 2005, astronomers discovered a large planet like object orbiting out beyond Pluto, eventually named eras after the Greek goddess of Strife and discord. The object is actually bigger than Pluto, and appears to be one of a half dozen other planet like objects found in the Kuiper Belt. And what about comets? And even before Pluto’s discovery comments were anomalies that were difficult to explain. In the scientifically minded 17 century Sir Isaac Newton described a clockwork universe with the orderly motion of the planets being the hands of a clock and the rational laws of nature the gears that drove them, there was no room in this universe for bodies that showed up at unpredictable times, stayed in the sky for a while and then disappeared. The best picture we have now of comets is that they are dirty snowballs, the central body of a comet is called the nucleus. When a comment is far away from the sun, the nucleus is frozen solid by the cold of space. As it approaches the sun though it heats up and the volatile materials in the nucleus begin to boil off. In the late 20th century spacecraft visited comets for the first time flying by and in one case, bringing material from the comet’s tail back to Earth, the Deep Impact spacecraft in 2005, and the Star Dust spacecraft in 2004 actually visited comets. So what about this Kuiper belt from Neptune’s orbit to about 55 au which is an astronomical unit, the AU is actually the average distance from the Earth to the Sun and is a standard unit of astronomical measurement. So from Neptune’s orbit to about 55 au now you understand what it is the solar system extends outward in a giant doughnut shaped structure known as the Kuiper Belt. The Kuiper Belt consists primarily of what appears to be planetesimals left over from the formation of the solar system since 1992. Telescopic exploration of the Kuiper belt has uncovered more than 1000 Kuiper Belt objects, and astronomers expect to find many more. One such object is Aries larger than Pluto and about 97 au from the sun, which is well outside of the Kuiper Belt proper, it is actually the farthest known member of our solar system. And finally, we will talk about the Oort cloud and with that, I will have covered everything I wanted to tell you about the solar system. So the Oort cloud, which is by the way, o r t, just in case you’re wondering, and it is actually named after the astronomer who discovered it. So that’s what happened in nine 1950 Dutch astronomer Yan ort suggested that somewhere in the solar system, there had to be a reservoir of comets. Today this reservoir is thought to consist of a huge cloud outside the Kuiper Belt named the Oort cloud. It extends from a few 1000 A you out to at least 50,000 au and perhaps farther, the Oort cloud is thought to be the remains of the original protoplanetary disk. And as befits a region, so remote and mysterious, there are many imaginative explanation for the origin of larger Oort Cloud objects, including the idea that they were captured from the Oort cloud of a passing star. But of course, we still don’t have a clue about what’s out there.

50:46
Maybe we will have in the years to come or in the few 100 years to come, so we will never know. But anyway, this was all about our solar system. And that was everything I wanted to share with you in today’s episode. I hope you’ll like our new series beyond Earth, and I hope you enjoy it. As much as I’m enjoying creating this series. Don’t forget that you can find the transcript on my website English plus podcast.com. The link is in the show notes. And also don’t forget that we have just started our new English plus premium program with one premium episode to match every single free episode we have in our podcast. So by becoming a patron on Patreon, you’ll get double the amount of episodes that you get from English plus but that’s not about it. We have some great series running in there you can check them out and I will be talking in more detail about all that in our brand new show at the end of the week plus doc show. Now with that being said I would like to thank you very much for listening to another episode from English plus podcast. This is your host Danny. I will see you next time.

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