Noctilucent Clouds Credit & Copyright: Pekka Parviainen (NCWG/U. Colorado) Explanation: Sometimes it's night on the ground but day in the air. As the Earth rotates to eclipse the Sun, sunset rises up from the ground. Therefore, at sunset on the ground, sunlight still shines on clouds above. Under usual circumstances, a pretty sunset might be visible, but unusual noctilucent clouds float so high up they can be seen well after dark. Pictured above, a network of noctilucent clouds casts a colorful but eerie glow visible above the dark. Although noctilucent clouds are thought to be composed of small ice-coated particles, much remains unknown about them. Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (USRA) NASA Technical Rep.: Jay Norris. LHEA at NASA/ GSFC & Michigan Tech. U.
Infrared Saturn Credit: E. Karkoschka (University of Arizona), HST, NASA Explanation: This delightfully detailed false color image of Saturn was earmarked to celebrate the 8th anniversary of the orbiting Hubble Space Telescope. The picture is a combination of three images taken in January 1998 and shows the lovely ringed planet in reflected infrared light. Different colors indicated varying heights and compositions of cloud layers generally thought to consist of ammonia ice crystals. The eye-catching rings cast a shadow on Saturn's upper hemisphere, while the bright stripe seen within the left portion of the shadow is infrared sunlight streaming through the large gap in the rings known as the Cassini Division. Two of Saturn's many moons have also put in an appearance, Tethys just beyond the planet's disk at the upper right, and Dione at the lower left. Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (USRA) NASA Technical Rep.: Jay Norris. LHEA at NASA/ GSFC & Michigan Tech. U.
A Martian Valley Credit: Malin Space Science Systems, MGS, JPL, NASA Explanation: This tantalizing close-up detail of a network of martian valleys was recorded from orbit this April by Mars Global Surveyor's camera. Water may once have flowed here but now sand dunes stripe the windswept valley floor. The Mars Global Surveyor spacecraft arrived in orbit in September of 1997 and has been exploring the red planet since. Three other spacecraft, Mars Climate Orbiter, Mars Polar Lander, and Nozomi are presently en route. Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (USRA) NASA Technical Rep.: Jay Norris. LHEA at NASA/ GSFC & Michigan Tech. U.
Jupiter from Voyager - Large Version! Credit: Voyager 1, NASA Explanation: This picture of the planet Jupiter was taken by the Voyager 1 spacecraft as it passed the planet in 1979. Jupiter, a gas giant planet with no solid surface, is the largest planet in the Solar System and is made mostly of the hydrogen and helium. Clearly visible in the above photo is the Great Red Spot, a giant, hurricane-like storm system that rotates with the clouds of Jupiter. It is so large three complete Earths could fit inside it. Astronomers have recorded this giant storm on Jupiter for over 300 years. Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (USRA) NASA Technical Rep.: Jay Norris. Specific rights apply. A service of: LHEA at NASA/ GSFC & Michigan Tech. U.