THE SOLAR SYSTEM By Denise Kerrigan for the

THE SOLAR SYSTEM By Denise Kerrigan for the Explorers Co-op

This image of Mercury’s southern hemisphere was taken by Mariner 10, on March 29, Image courtesy of NASA 1974.

Due to its lack of atmosphere, Mercury is the most heavily cratered planet in the solar system. Image courtesy of NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

o Mercury has very little gravity. If you weighed 100 lbs here on Earth, you would only weigh 38 lbs on Mercury! o Mercury is only visible from Earth 13 times every 100 years! We won’t be able to see it again until 2016! o Temperatures on Mercury range from 800º F to -290º F! Because it has such a thin atmosphere, it cannot retain its heat, even being that close to the Sun. Image courtesy of NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

With all it’s clouds, Venus is a super greenhouse, reaching temperatures of 870ºF! It’s the hottest planet! Image Courtesy of NSSDC Photo Gallery

Taken by the Magellan spacecraft in 1991, this shows the craters and volcanic activity on Venus is covered by thousands of volcanoes. Image courtesy of NASA/JPL

o Sometimes referred to as the morning or evening star, Venus is the third brightest object in the sky, after the Sun and Moon. It looks more than 10 times brighter than the brightest star, Sirius. o Venus has a retrograde rotation, which means it rotates on its axis backwards. o The clouds on Venus are made up of sulfuric acid and the air is made up mostly of carbon dioxide. o One day on Venus lasts for 243 Earth days!

Earth is the only planet we know of that supports life. Image courtesy of NASA/NSSDC

This was taken from Apollo 11, in 1969, and shows the earthrise over the moon! Image courtesy of NASA/JPL

o This image of a thunderstorm was taken in 2000 from the International Space Station. o The Earth spins on its axis at 1, 000 miles per hour! o Earth is the only planet that has water as a solid, liquid, and gas. o The Earth’s axis is tilted 23. 5º, and that is what gives us seasons. o The air we breathe is made up mostly of Nitrogen. In fact, it is 77% Nitrogen and only 21% Oxygen! Image courtesy of Science & Analysis Laboratory, NASA Johnson Space Center

o The dark areas on the moon are called maria (mär΄-ē-ə). They are generally flat areas, and were once believed to be seas. The light areas are called terrae (ter –ē). These areas are generally more rugged and with many more craters. o If it weren’t for the moon, Earth’s rotation, and even the weather, would be out of control. o We only ever see one side of the moon from Earth. The dark side of the moon always faces away from Earth, and is much more heavily Image courtesy of NASA cratered.

Mars appears red because the soil is made up of large amounts of iron, which has rusted. Image courtesy of NASA (Taken by the Hubble Space Telescope. . )

Scientists have found water ice on Mars, particularly on its northern and southern poles. Image courtesy of ESA/DLR/FU Berlin (G. Neukum)

o Mars is the home to the largest volcano in the Solar System, Olympus Mons. The volcano is approximately 20 miles high, and has a diameter of 374 miles. Olympus Mons is about the size of the state of Arizona. o Mars is also the home to the longest and deepest canyon in the Solar System. Valles Marineris is 2, 485 miles long, 124 miles wide, and up to 4 miles deep. o Mars has terrible dust storms that can sometimes cover the entire planet. o Mars’ two moons are captured asteroids, Phobos and Deimos. Phobos is slowly spiraling down, into Mars. Image courtesy of NASA/NSSDC Photo Gallery

Found between Mars and Jupiter, the Asteroid Belt contains most of the asteroids in the Solar System. Most asteroids are very irregularly shaped and have craters on them. The Asteroid Belt contains millions of asteroids, which are very spread out. Image courtesy of NASA/Lunar and Planetary Institute

This image shows the gas giant Jupiter with one of its moons, Europa, passing in front of it. Image Courtesy of NASA/JPL/University of Arizona

Jupiter’s Giant Red Spot is a huge storm that has been raging on the planet for more than 400 years! Image courtesy of NASA Planetary Photojournal

o This image shows Jupiter with one of its moons, Io. o Jupiter has 64 known moons. The four largest, called the Galilean moons, are Io, Europa, Callisto, and Ganymede. o The dark stripes on the planet are called belts and the light strips are called zones. They are created by winds in Jupiter’s upper atmosphere. o Jupiter’s rings weren’t discovered until 1979, and are only visible with backlight from the Sun. o The Giant Red Spot is so big that three Earths inside of it! Image courtesy of NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute/GSFC

Saturn is the most distant planet that we can see with the naked eye! Image courtesy of Space Telescope Science Institute

This shows Saturn in an edge on view, with four of its moons passing in front of it. Image courtesy of NASA/JPL/STSI

o Saturn’s rings are only about 30 feet thick! o The rings are made up of tiny particles of dust and ice, ranging in size from a grain of salt to a giant boulder! o Saturn has 62 known moons! o Some of Saturn’s moons orbit in opposite directions around Saturn. o Saturn’s moon Iapetus has one hemisphere that is white, and one that is black! It is called the yin and yang of Saturn’s moons. o Saturn’s gravity is close to Earth’s. If you weigh 100 pounds on Earth, you would only weigh 107 pounds on Saturn! Image courtesy of NASA.

Uranus has a 98º tilt to its axis, and is the only planet in the Solar System tilted completely on its side. Image courtesy of NASA/Space Telescope Science Institute

Uranus’s rings are also tilted sideways, staying aligned with the planet’s equator. Image courtesy of Erich Karkoschka (University of Arizona) and NASA

o Uranus was discovered in 1781 by British astronomer, William Herschel. It was the first planet discovered in over 2000 years! o Herschel originally wanted to name the planet Sidus Georgium, after King George III. o Scientists believe that Uranus was hit by a very heavy object early in its existence, and that is what caused it to tip on its side. o This shows Uranus with one of its moons, Ariel. o Because of its tilt, Uranus experiences 42 years of winter followed by 42 years of summer, as it travels around the Sun! Image courtesy of NASA/Space Telescope Science Institute

Neptune is the farthest planet from the Sun and is the smallest of the gas giants. Image courtesy of NASA

Neptune’s Great Dark Spot is a giant storm, much like Jupiter’s Giant Red Spot, and is about the size of Earth. Image courtesy of JPL/NASA Planetary Photojournal

o Neptune was predicted mathematically to exist before it was actually found. Two people are credited with its discovery in the 1840’s, French mathematician Urbain Le Verrier, and British astronomer John Couch Adams. In September of 1846, German astronomer, Johann Galle, found it with a telescope using the predictions. o Neptune has the wildest weather of any planet in the Solar System. Temperatures can reach as low as 350ºF, even though its core is hotter than the Sun’s! Neptune also has terribly violent winds that can reach 932 mph! Giant hurricanes are also extremely common. o The Voyager 2 spacecraft reached Neptune in 1989, and is the only spacecraft to ever travel to Neptune. Image courtesy of NASA Planetary Photojournal

In August of 2006, the International Astronomical Union defined the term planet for the first time. When this happened, a new planetary category was created: dwarf planet. Pluto’s status as the ninth planet was suddenly changed, and it was reclassified as a dwarf planet. Now, Pluto, along with four other known objects are considered dwarf planets. Scientists believe there may be as many as 100 other dwarf planets in our Solar System, just waiting to be discovered. This image is an artist’s depiction of some of the dwarf planets compared to Earth and the Moon. Image courtesy of NASA

Ceres is the only known dwarf planet that is not part of the Kuiper Belt. Ceres is found in the asteroid belt, and is the only round object discovered there. Scientists think the area surrounding the core of Ceres may be made of water ice. Ceres is named for the Roman goddess of corn and harvests. Image courtesy of NASA/ESA/SWRI/Cornell University/University of Maryland/STSci

Once the ninth planet of the Solar System, Pluto is now perhaps the most well known dwarf planet. Pluto was discovered in 1930 by American astronomer Clyde Tombaugh. Pluto was named by an 11 year old English girl and was named for the Roman god of the underworld. This image, from the Hubble Space Telescope, shows Pluto with three of its moons. Image courtesy of NASA/Hubble Space Telescope

The dwarf planet Makemake, discovered in 2005, is part of the Kuiper Belt. Makemake was named after the Rapanui (people of Easter Island) god for fertility. The methane and ethane in its atmosphere, mixed with solar ultraviolet light, produce the red-brown color we see. Image courtesy of Princeton University

Also part of the Kuiper Belt, Haumea was discovered in 2003. Haumea was named after the Hawaiian goddess of childbirth and fertility. Haumea is one of the fastest rotating objects in our Solar System. It rotates on its axis once ever 4 hours! Image courtesy of NASA

Eris is another Kuiper Belt object, and was discovered in 2003. Eris was originally labeled the tenth planet in the Solar System, but that didn’t last for long. The discovery of Eris sparked the debate which eventually led the IAU to define what a planet was and create the classification of dwarf planet. This artist’s conception shows Eris with its moon. That bright star in the background is the Sun! Eris is named after the Roman goddess Image courtesy of Cal. Tech

The Kuiper Belt is an area beyond Neptune, somewhat like the Asteroid Belt between Mars and Jupiter, but much larger. It’s filled with rocky and icy objects, some of which are dwarf planets. It is also believed to be where many comets, such as Halley’s Comet, come from. Image courtesy of NASA

The Oort Cloud is an area extending trillions of miles beyond the Kuiper Belt and Solar System. It contains trillions of icy objects that interact with other parts of our galaxy. Occasionally, some of those interactions will send a comet into the inner Solar System. Those are the comets that appear to us only once in thousands of Image courtesy of NASA years.

Beyond Our Solar System Image courtesy of NASA, ESA, STSc. I, J. Hester and P. Scowen (Arizona State University)

Inside our own Milky Way galaxy, there are billions of stars. We know of over 400 with planets orbiting them. Image courtesy of Kuiper Airborne Observatory

There are countless galaxies beyond our own, and billions of stars in each one. Could one have an Earth-like planet orbiting? Image courtesy of Robert Williams and the Hubble Deep Field Team (STSc. I) and NASA

There are many wonders in the heavens to behold! Image courtesy of University of California Santa Cruz

Many new things to discover! Image courtesy of NASA, ESA, and The Hubble Heritage Team

Glorious creations! Image courtesy of NASA, ESA, and M. Livio

Who knows what we will find next! Image courtesy of NASA, ESA, and M. Livio and the Hubble 20 th Anniversary Team