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With Explore the Planets, investigate the planets, their moons, and understand the processes that shape them. By G. Jeffrey Taylor, Ph.D. See our DVD collection.

Planets

By the current count of astronomers, our solar system includes 8 planets and 5 dwarf planets. The planets were formed during the process of solar system formation, when clumps began to form in the disk of gas and dusk rotating about our young Sun. Eventually, only the planets and other small bodies in the solar system remained. The four rocky planets at the center of the solar system Mercury, Venus, Earth, Mars, are known as the inner planets. Jupiter, Saturn, Uranus, and Neptune are all composed primarily of gas and are known as the outer planets. Find out more about the planets through the links below.

A view of the Earth as seen by the <a href="/space_missions/apollo17.html&dev=1">Apollo
17</a> crew
while traveling to the
<a href="/earth/moons_and_rings.html&dev=1">Moon</a> on
December 7, 1972.  Africa, Madagascar, and the Arabian Peninsula are
visible, and you can barely make out the
<a href="/earth/polar/antarctica.html&dev=1">Antarctic</a>,
shrouded in the heavy
<a href="/earth/Atmosphere/cloud.html&dev=1">cloud</a> cover
in the southern hemisphere.
Arching cloud patterns show the presence of <a href="/earth/Atmosphere/front.html&dev=1">weather
fronts</a>.<p><small><em>Image courtesy of NASA/Apollo 17.</em></small></p>Have you ever seen the <a href="/earth/Magnetosphere/aurora.html&dev=1">Southern or Northern Lights</a>? Earth isn't the only planet that puts on these beautiful light shows, which are also called the "<a href="/earth/Magnetosphere/aurora.html&dev=1">aurora</a>". Aurora have been seen at both <a href="/saturn/saturn_polar_regions.html&dev=1">poles of Saturn</a>, too, as well as at the poles of <a href="/jupiter/magnetosphere/jupiter_aurora.html&dev=1">Jupiter</a>.  These "<a href="/earth/Magnetosphere/tour/tour_earth_magnetosphere_09.html&dev=1">curtains of light</a>" sometimes rise 1,200 miles (2,000 km) above the <a href="/saturn/atmosphere/S_clouds_overview.html&dev=1">cloud tops</a> near Saturn's poles. The <a href="/space_missions/HST.html&dev=1">Hubble Space Telescope</a> took this picture in 2004.<p><small><em>Image courtesy of NASA, ESA, J. Clarke (Boston University), and Z. Levay (STScI)</em></small></p>Neptune's <a href="/neptune/lower_atmosphere.html&dev=1">atmosphere</a> shows
a striped pattern of
<a href="/neptune/atmosphere/N_clouds_overview.html&dev=1">clouds</a>.
This cloud pattern is very similar to that of
<a href="/jupiter/jupiter.html&dev=1">Jupiter</a> and
<a href="/saturn/saturn.html&dev=1">Saturn</a>.
Neptune even has a <a href="/neptune/atmosphere/N_clouds_GDS.html&dev=1">Great Dark
Spot</a> similar
to Jupiter's <a href="/jupiter/atmosphere/J_clouds_GRS.html&dev=1">Great
Red Spot</a>.
The Great Dark Spot of Neptune is thought to be a hole, similar to the hole
in the <a href="/earth/Atmosphere/ozone_layer.html&dev=1">ozone layer on
Earth</a>,
in the <a href="/physical_science/chemistry/methane.html&dev=1">methane</a> cloud
deck of Neptune.<p><small><em>Image courtesy of NASA</em></small></p><a href="/mercury/mercury.html&dev=1">Mercury</a>, the innermost planet of the solar system, is a little bigger than the Earth's Moon. The <a href="/mercury/Interior_Surface/Surface/surface_overview.html&dev=1">surface</a> of the planet is covered with craters, like the Moon, but temperatures there can reach over 800&deg;F because Mercury is so close to the Sun and rotates so slowly.  This picture was taken by the <a href="/space_missions/robotic/messenger/messenger.html&dev=1">MESSENGER spacecraft</a> in October 2008.<p><small><em>Image courtesy of NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington.</em></small></p>This historic image is the first ever taken from a spacecraft in orbit about <a href="/mercury/mercury.html&dev=1">Mercury</a>, the innermost planet of the solar system.  Taken on 3/29/2011 by <a href="/space_missions/robotic/messenger/messenger.html&dev=1">MESSENGER</a>, it shows numerous craters across the <a href="/mercury/Interior_Surface/Surface/surface_overview.html&dev=1">surface</a> of the planet.  Temperatures there can reach over 800°F because Mercury is so close to the Sun and rotates so slowly.  MESSENGER entered orbit around Mercury earlier in March 2011.<p><small><em>NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington</em></small></p>New observations by the MESSENGER spacecraft provide  support for the hypothesis that Mercury harbors abundant water ice and other frozen volatile materials in its permanently shadowed (shown in red) polar craters. Areas where polar deposits of ice imaged by Earth-based radar are shown in yellow.<p><small><em>Image courtesy of NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington/National Astronomy and Ionosphere Center, Arecibo Observatory</em></small></p>

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Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part is sponsored in part through grants from federal agencies (NASA and NOAA), and partnerships with affiliated organizations, including the American Geophysical Union, the Howard Hughes Medical Institute, the Earth System Information Partnership, the American Meteorological Society, the National Center for Science Education, and TERC. The American Geophysical Union and the American Geosciences Institute are Windows to the Universe Founding Partners. NESTA welcomes new Institutional Affiliates in support of our ongoing programs, as well as collaborations on new projects. Contact NESTA for more information. NASA ESIP NCSE HHMI AGU AGI AMS NOAA