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6. Neptune and Triton


This dramatic view of the crescents of Neptune and Triton was acquired by Voyager 2 approximately 3 days, 6 and one-half hours after its closest approach to Neptune (north is to the right).

The encounter put the spacecraft on a couse plunging southward at an angle of 48° to the plane of the ecliptic. This direction, combined with the current season of southern summer in the Neptune system, gives this picture its unique geometry.

The spacecraft was at a distance of 4.86 million km (3 million miles) from Neptune when these images were taken so the smallest detail discernible is approximately 90 km (56 miles). Color was produced using images taken through the narrow-angle camera's clear, orange and green filters. Neptune does not appear as blue from this viewpoint because the forward scattering nature of its atmosphere is more important than its absorption of red light at this high phase angle (134°).

7. Asteroid Vesta in a 'Rainbow-Colored Palette'


Vesta appears in a splendid rainbow-colored palette in new images obtained by NASA's Dawn spacecraft. The colors, assigned by scientists to show different rock or mineral types, reveal Vesta to be a world of many varied, well-separated layers and ingredients. Vesta is unique among asteroids visited by spacecraft to date in having such wide variation, supporting the notion that it is transitional between the terrestrial planets -- like Earth, Mercury, Mars and Venus -- and its asteroid siblings.
In images from Dawn's framing camera, the colors reveal differences in the rock composition associated with material ejected by impacts and geologic processes, such as slumping, that have modified the asteroid's surface. Images from the visible and infrared mapping spectrometer reveal that the surface materials contain the iron-bearing mineral pyroxene and are a mixture of rapidly cooled surface rocks and a deeper layer that cooled more slowly. The relative amounts of the different materials mimic the topographic variations derived from stereo camera images, indicating a layered structure that has been excavated by impacts. The rugged surface of Vesta is prone to slumping of debris on steep slopes.
Dawn scientists presented the new images at the American Geophysical Union meeting in San Francisco on Monday, Dec. 5. The panelists included Vishnu Reddy, framing camera team associate, Max Planck Institute for Solar System Research, Katlenburg-Lindau, Germany; Eleonora Ammannito, visible and infrared spectrometer team associate, Italian Space Agency, Rome; and David Williams, Dawn participating scientist, Arizona State University, Tucson.
"Vesta's iron core makes it special and more like terrestrial planets than a garden-variety asteroid," said Carol Raymond, Dawn's deputy principal investigator at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "The distinct compositional variation and layering that we see at Vesta appear to derive from internal melting of the body shortly after formation, which separated Vesta into crust, mantle and core."
The presentation also included a new movie, created by David O'Brien of the Planetary Science Institute, Tucson, Ariz., that takes viewers on a spin around a hill on Vesta that appears to be made of a distinctly darker material than the rest of the crust.

8. A New Line of Stellar Evolution


This graphic gives a summary of our best current understanding of the evolution of stars, showing their birth, middle age and eventual demise. The lowest mass stars are shown at the bottom and the highest mass stars at the top. The very top line is a new addition, compelled by the detection of SN 2006gy -- one of the brightest stellar explosions ever recorded -- that describes the evolution of the most massive stars in the universe. Observational evidence for the special type of explosion shown here -- which is incredibly bright and obliterates the star rather than producing a black hole -- was lacking until SN 2006gy was found.

9. Hartley 2


This close-up view of comet Hartley 2 was taken by NASA's EPOXI mission during its flyby of the comet. It was captured by the spacecraft's Medium-Resolution instrument.

10. Two Views of Mercury


This composite image of Mercury's Caloris basin was created with pictures from Mariner 10 (right portion) and MESSENGER images.


By Apress on June 5, 2012 ®