30 April 2013, 07:14 PM ET
The world's time zones and hemispheres are divided into east and west by the prime meridian at the Royal Observatory in Greenwich.
26 April 2013, 04:32 PM ET
Lowell Observatory is best known for the discovery of Pluto. Astronomers there have also studied Halley's Comet and discovered an exoplanet in 2007.
25 April 2013, 04:39 PM ET
After years competing in spaceflight, the United States and the Soviet Union did a joint mission for the first time in 1975.
24 April 2013, 03:33 PM ET
The moons of Saturn — 62 in all — come in a variety of sizes and compositions.
24 April 2013, 07:13 AM ET
Since launch in 1990, the Hubble Space Telescope (HST) has provided amazing images that have led to discoveries. Explore Hubble's history and facts.
23 April 2013, 03:26 PM ET
Eugene Cernan, the last Apollo astronaut to walk on the moon, left something behind: his daughter's initials in the dust.
23 April 2013, 03:22 PM ET
Harrison "Jack" Schmitt was the first trained scientist, rather than a former test pilot, to go to the moon. He collected evidence of volcanic activity during the Apollo 17 mission.
23 April 2013, 03:19 PM ET
As command module pilot, Ron Evans spent more time orbiting the moon than any other astronaut.
22 April 2013, 05:51 PM ET
Hyperion is a potato-shaped moon of Saturn with an erratic rotation and eccentric orbit.
19 April 2013, 05:30 PM ET
Numerous craters on Saturn's moon Tethys shine brightly, suggesting the presence of water-ice.
18 April 2013, 05:44 PM ET
The contrast between its light and dark faces keeps Saturn's moon Iapetus hidden in shadows.
16 April 2013, 02:18 PM ET
Charlie Duke was the voice on the radio talking to the Apollo 11 crew during landing. A few years later, he walked on the moon himself on Apollo 16.
16 April 2013, 02:16 PM ET
Astronaut John Young, the ninth man to walk on the moon, flew on three NASA programs: Gemini, Apollo and the space shuttle.
16 April 2013, 02:08 PM ET
Ken Mattingly missed his ride on Apollo 13, but made it to the moon on Apollo 16. He also commanded two shuttle missions.
12 April 2013, 02:29 PM ET
With a giant crater covering much of its surface, Mimas resembles a real-life Death Star from the "Star Wars" movies.
09 April 2013, 01:53 PM ET
Rhea, Saturn's second-largest moon, has a wispy oxygen atmosphere.
08 April 2013, 06:15 PM ET
David Scott's mission to the moon focused on science and featured the first lunar road trip.
08 April 2013, 06:10 PM ET
Jim Irwin wanted to fly to the moon since he was a child. Aboard Apollo 15, he made it.
08 April 2013, 06:01 PM ET
Al Worden's discovery that he liked to fly planes led him to becoming an astronaut and piloting the Apollo 15 command module.
05 April 2013, 06:25 PM ET
The tiny moon Enceladus is one of the most promising potential sites for hosting life in the solar system.
04 April 2013, 02:53 PM ET
Pete Conrad overcame dyslexia to become one of NASA's most-traveled astronauts, logging four trips into space, including Apollo 12.
04 April 2013, 02:49 PM ET
Alan Bean walked on the moon during Apollo 12. He turned to painting to chronicle his experiences.
04 April 2013, 02:44 PM ET
Richard F. "Dick" Gordon orbited the moon on Apollo 12. Earlier, he helped astronauts learn how to spacewalk.
02 April 2013, 03:52 PM ET
A collision may have spun Saturn's fourth moon around 180 degrees.
29 March 2013, 06:17 PM ET
This 2,500-mile system is one of the larger canyons in the solar system.
27 March 2013, 07:00 PM ET
The two small bodies that orbit the red planet raise a number of questions about the formation of the early solar system.
26 March 2013, 03:11 PM ET
Ed Mitchell's experience aboard Apollo 14 launched his exploration of the nature of human consciousness.
26 March 2013, 03:02 PM ET
Stuart Roosa's skills were put to the test when a docking mechanism didn't work.
21 March 2013, 06:52 PM ET
The moon's orbit brings it 6 feet closer to the red planet every century.
21 March 2013, 06:48 PM ET
Deimos' radius is only 3.9 miles. The tiny moon zips around Mars in only 30 hours and is so close to its parent planet that it was missed for centuries.
20 March 2013, 03:27 PM ET
Jim Lovell was for years NASA's most-traveled astronaut. He flew on four missions, including Apollo 13, whose crew had to survive in space after a crippling explosion.
20 March 2013, 03:22 PM ET
Jack Swigert survived the perilous Apollo 13 mission, then took a different kind of risk: entering politics.