NEW - A Tour of the Solar System is now available for Google Earth here!!
Also available as a Word Document and a SOS playlist
1. NOAA Logo
Welcome to NOAA's Science On a Sphere. You are looking at the world's first spherical movie screen. This is not a hologram; it's a 6-foot, free hanging plastic ball, which is carbon-reinforced. The system uses special software to render videos for the spherical surface and four projectors. Science On a Sphere is the invention of Dr. Alexander MacDonald, of the National Oceanic and Atmospheric Administration. Now let's go on a short tour of the Solar System!
2. X-Ray Sun
The first stop is the sun, a giant ball of burning gas and the closest star to Earth. The matter in the sun comprises about 99.8% of all the matter in the solar system. The remaining .2% goes to all the other planets and moons and the asteroid belt. The Sun is an astonishing 861,800 miles in diameter. The sun is also a huge thermonuclear reactor. At its core, the process of nuclear fusion, which is simply hydrogen atoms fusing together to form helium, is constantly taking place. This creates a great deal of heat and energy, which we benefit from here on Earth. Fusion has been occurring in the Sun for about four and a half billion years, and there is enough energy in it to last about another four and a half to five billion years, so the Sun is at about half of its life span. Since the sun is not a solid object, the equator, or center, actually rotates faster than the polar areas by about 10 days. What you see here is the corona, or the outer layer, of the sun. You never want to look directly at the real Sun, but its okay to look at this video of it. While the sun's brilliant surface is about 10,000°F, the thin outer corona is much hotter at about 1,000,000°F. The bright yellow flashes of light you see are actually solar flares. These are storms on the surface of the sun. Scientists at NOAA watch for these flares because they can create problems here on Earth. The high-energy particles and radiation from the solar flares excite the upper atmosphere of Earth, the part we call the ionosphere, and the outer magnetosphere. This can interfere with communications like cell phones and satellites. The high-energy particles and radiation also create the Aurora Borealis, or Northern Lights.
Next on our tour is Mercury, the planet closet to the sun. Or, half of Mercury. We've only seen one side because it rotates very slowly, and spacecraft so far have always flown by at similar vantage points. Mercury rotates three times for every two orbits around the sun. And since it's only 36 million miles from the Sun, it's too hot for us to send a spacecraft to the sunny side of Mercury. Mercury is so close to the sun that its orbit is only 88 days. You might be noticing that Mercury looks a lot like the moon. That's because it doesn't have an atmosphere, just like the moon. One thing an atmosphere does for a planet is provide protection from meteors and rocks. Without an atmosphere to protect Mercury, it has become covered with craters. Another result of not having an atmosphere is a sharp temperature contrast. The sunny side of Mercury is about 800°F, while the cool side, or the side facing away from the Sun is a much colder 300°F below zero; a sharp contrast of about 1100°F. As u'll find out on this tour of the Solar System, there are not many hospitable places to live other than Earth. These pictures of Mercury were taken by the Mariner Spacecraft in 1974 and 75.
Now, on to Venus. Actually, this is a radar brightness image of Venus. This video doesn't show the atmosphere of Venus, which is quite thick, and made of sulfuric acid clouds. The brighter spots are often rougher terrain. Venus is a very volcanic place. The atmosphere is comprised mainly of carbon dioxide. Venus has about 25,000 times the CO2 of Earth. And that much CO2 does two things. First, it creates a runaway Greenhouse Effect. The CO2 traps infrared radiation, or heat that normally travels out to space. So it's very HOT on Venus, in fact, i's the hottest planet in the solar system at 900°F! Second, the atmospheric pressure is really high on Venus. It's about 92 times as much as our air pressure. This is about the pressure a deep sea diver would encounter at a depth of 3000 feet underwater. So if you were on Venus you'd be compressed to about the size of a toothbrush. Hot and squished, not a fun place to live. At one point, Venus may have had oceans, but they've since evaporated and been lost to outer space. Its orbit is 225 days, and its distance from the sun is about 67 million miles. Because Venus is the brightest planet, it is often the evening star in the sky. Of course, it's not really a star.
5. Earth: The Blue Marble
Our next stop should be a familiar place, the Earth. The orbit of Earth, which is the length of one year, is 365.26 days; because of this we have to rearrange our calendar with Leap Days and Leap Years to make it come out right. This is a picture of the Earth over three days, which at any time is about 50% covered in clouds. You can see the continents in green and brown and the oceans in blue. This is just what it would look like if you were an astronaut in outer space. The Earth's tilt is 23.5°, which gives us our seasons. During the summer (in the Northern Hemisphere), we are tilted toward the sun, causing temperatures to rise. The Earth is about 8,000 miles wide, and it gets the most sunlight at the equator, on average. All of the Earth's weather is caused by what we call differential heating, which just means that some parts of the Earth, such as the equator, get more heat from the sun than others. This temperature imbalance has to be worked out by wind and weather patterns. We're 93 million miles from the Sun, and the Earth is 71% water, about 29% land. Notice that the Earth is not covered in craters because there is an atmosphere to provide protection.
6. Earth's Moon
The moon, however, does not have an atmosphere to protect the surface from meteors and rocks. This is the cause of the marked up surface. The Moon doesn't shine with its own light. It reflects sunlight, so it's like a big mirror in the sky. The moon is about 1/4th the diameter of Earth, and 1/80th of the mass. The temperature range is pretty great; the side of the Moon that always faces us, the sunny side, is 253°F while the dark side i -387°F, making a difference of over 600°F! The Moon is mainly responsible for the tides of the oceans, and it goes through its phases from full to new, and back to full again in about 28 days. Neil Armstrong was the first person to walk on the moon, on July 21 (the Apollo 11 landed on the moon on July 20), 1969. The moon's a pretty dusty, rocky, plain place. The astronauts said the dirt felt like snow, but smelled like spent gunpowder. That's because i's made of a silicate rock, which apparently made the command module return flight a little smelly. We may get to go back to the moon, and maybe we'll have our first girl walk on the moon. In 2004, President Bush signed an initiative for NASA to go back for longer missions to the moon.
Now, this is the Red Planet, Mars. It is red because of the iron oxide dust on its surface, which has the consistency of talcum powder. We are exploring Mars currently more than any other planet. There are 3 orbiting spacecraft, and 2 exploration rovers, Opportunity and Spirit, currently on the surface. Both were designed for several months study, but they're still going after 4 years. We'll be learning even more about Mars when the Phoenix lander makes it there in May of 2008. The next mission may discover more about if life ever existed on Mars, because it will go closer to these... (TILT MARS) These are ice caps; the northern one is larger. They're made of frozen water, normal ice and carbon dioxide. (REORIENT) Mars has a couple of very interesting features. This deep long scar is the Valles Marineris. It is the biggest canyon known in the Solar System. Its 2500 miles across, the distance from New York to Phoenix, and it is 5.7 miles deep. The Grand Canyon, for comparison, is only 1 mile deep. Another record-breaking feature of Mars is Olympus Mons. It is the largest mountain (and volcano) known in the Solar System. Its over 85,000 feet high! The highest point on Earth is Mt. Everest, which is about 29,000 feet, so Olympus Mons is almost three times that height. It was able to achieve such an impressive height because there are no plate tectonics on Mars. The volcano that created Olympus Mons continued to pile up solid material without the plates below it moving, unlike our Hawaiian island chain which is the result of moving plates.
Our next stop on this solar system tour is the largest planet. Jupiter has a diameter 11 times that of Earth. If you took all the other planets and smashed them together, Jupiter would still be larger. We are now at a distance of 482 million miles from the Sun. This video of Jupiter is based on photographs from the Cassini spacecraft that flew there in 2000. It may have a solid core about the size of Earth, but mostly it's a gas giant. Its motion is very fast (though slower than the inner planets). It travels around the sun in only 12 years, which is pretty quick. And it rotates at an incredible speed, completing one rotation in just 9 hours and 50 minutes. In fact, Jupiter, which has the fastest rotation rate in the solar system, bulges at the equator and flattens at the poles due to its rapid rotation. For something that large, that's quite a spin. Since it is primarily gas, there's some pretty wicked weather on Jupiter. That' what formed this... the GREAT RED SPOT. It is a huge storm. It's similar to a hurricane of sorts that is the SIZE of the Earth! And it has been going on for over 325 years!
The fifth moon of Jupiter is probably the most interesting visually. This is Io, the third largest moon of Jupiter. We call it the pizza moon, because that is what it looks like. The black circles are volcanoes; Io has over 400 of them. Because of the strong pressure within Io from being pulled by Jupiter and its other moons, these volcanoes send up sulfur-rich deposits; some of the sulfur dioxide then falls like snow coating the moon. There is little possibility of life on Io. But amino acids could possibly form there because of the rich nutrients. We'd like to explore Io more, and the New Horizons spacecraft just flew by Io on its way to Pluto.
Compared to Io, life is more likely on the sixth moon of Jupiter, Europa. It is thought that there is a global sub-surface ocean in Europa that is about 12 miles beneath the surface and up to 62 miles deep. This underground ocean is nutrient rich, providing a place for amino acids to form. Europa is roughly the size of the Earth's moon. There are relatively few craters on Europa because the surface of the moon is young. The young surface is composed mainly of water ice with various impurities embedded within. The mysterious linear features are from stresses that are largely tidally generated.
This next planet might look unfamiliar to you without its rings. Saturn, known for its rings, is the 6th planet from the sun and the 2nd largest. The rings of Saturn are made of ice, dust, and rock, with about 60 moons embedded within them. There are 3 main bands of the rings, which extend between 4,000 and 100,000 miles outward from the equator. If we showed them here on the scale of the SOS, they would only be about the thickness of a bacterium (100 nanometers). Saturn also rotates really fast, spinning around in about 10 hours. It has wind speeds up to 1,100 miles per hour. Saturn is about 900 million miles away from the Sun, which is about 10 times further away than the Earth is from the sun. It's a gas giant, made of hydrogen and helium. Saturn's core has a temperature of 21,400°F and it radiates more heat and energy out to space than it receives from the Sun. The Cassini spacecraft has been studying Saturn since 2004, and by 2008 will have made 70 trips around it! In all of these trips we have found out something fascinating about Saturn that we never knew before! At the North Pole, there is a gigantic hexagon! This is a 6 sided vortex with winds of 200 miles per hour. On the South Pole, a storm with a well defined eyewall was discovered. This is the first known eyewall to exist outside of Earth.
Let's move on to the whitest object in the whole solar system! This ice moon of Saturn is Enceladus. Since this has frozen water on it, there's the possibility that life could have, or may still exist on (or within) it. Not human life, but perhaps amino acids. Because it's an ice moon, it's very cold. However, the coolest thing about Enceladus is that there are about 20 gigantic geysers bursting out of its south pole! These are plumes of liquid water and steam. It seems that the gravitational torque inside the moon heats up and cracks the southern surface. This causes gases and liquid to be ejected from the moon. What scientists have discovered is that it's this exhaust from Enceladus that created the E-ring around Saturn! We'd like to explore this icy moon more.
The next stop is the largest moon of Saturn, Titan. It's 50% bigger than our moon, and even bigger than Mercury. The atmosphere is primarily nitrogen and methane which is similar to the atmosphere of early Earth. This might be an indicator that life (or at least important biological molecules) could have formed on Titan! Researchers have taken those two gases, and put them in a chamber. Then, they shined ultraviolet light and radiation like sunlight through them, and zap! Amino acids were formed; the building blocks of life. The atmosphere that encircles the moon creates a surface pressure 50% greater than that around Earth. The combination of gases in Titan's atmosphere, mixed with sunlight, has created thick smog around the moon, similar to that seen over large cities. There's no liquid water on Titan. Also, it's -300°F which makes it very cold. But there are hydrocarbon lakes at its North Pole. The Huygens probe landed on the surface, and found that it was some kind of goo! Not solid, not liquid, but a pudding like goo. Cassini is continuing periodic flybys of Titan building up a more detailed picture of its surface. Prior to the Cassini flybys, a clear view of Titan's was not available.
We now come to the two blue planets. This first one is Uranus. It's blue (or greenish) because of methane in its atmosphere. William Herschel discovered it in relatively recent times in 1781. It has a very high mass and density, and is made of frozen water, ammonia, and methane. On our tour, we are now 2 billion miles from the Sun, so Uranus' temperature is a very chilly -323°F. It has an 84-year orbit around the Sun. What makes Uranus so unique is that while most of the other planets revolve around their axis and spin like a top in just about the same plane as they orbit the Sun, Uranus has a 98-degree tilt. So it rolls over and over itself as it travels around the Sun.
Now, on to the other blue planet, Neptune. It's also blue from methane in its atmosphere, along with a lot of hydrogen and helium. When this picture was taken by the Voyager spacecraft, Neptune had a dark spot caused by a storm, like Jupiter's Great Red Spot. Unlike Jupiter's Great Red Spot, the storm on Neptune is not persistent or stationary. The storm was first discovered in the Southern Hemisphere, but when the Hubble Telescope photographed the planet later, the Southern Hemisphere storm was gone and a new storm had formed in the Northern Hemisphere. Neptune is also a very unpleasant place to live. Its temperature is 353°F below zero! And it has winds of up to 1200 miles per hour! There is a group of white clouds referred to as The Scooter which races around the planet every 16 hours. It's a very windy place, though the theories about what powers the winds are all somewhat speculative. It is thought that the very hot core of Neptune might play a part in the strong surface winds. Researchers are trying to learn more about its hot core, and the cause of the winds.
This is the last stop on our tour of the Solar System, but this is no longer a planet, it's a dwarf planet. This is Pluto. Unfortunately, this is currently our best picture of Pluto. Because Pluto is an astounding 3,670,050,000 miles from the sun, it is hard to get close enough to get a good picture. This picture was taken by the Hubble Telescope (with some Earth-based color information added). We're going to get a better look at Pluto with the New Horizons spacecraft, which will pass Pluto in 2015. It's made of rock and ice, and is 1,400 miles wide. Until 2006, it was the 9th planet. But in that year, the International Astronomical Union set up new guidelines for what it takes to be a planet. There are 3 things you need:
You have to be in orbit about the Sun, which Pluto is.
Next, you have to have enough gravitational pull of your own to retain a spherical shape, whether you're made of gas or solid. And Pluto does do that.
But, it does not pass the third test. You have to have swept out everything else within your path around the Sun. Pluto is not dominant enough to have done that, because there are larger objects within and beyond its orbit in the Kuiper belt. Here's the wording: a planet will have cleared the neighbourhood of its own orbital zone, meaning it has become gravitationally dominant, and there are no other bodies of comparable size other than its own satellites or those otherwise under its gravitational influence.
Now that we have visited Pluto, our tour of the Solar System on Science On a Sphere is complete. Thank you for joining NOAA on this exciting journey.