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Tag Archives: Voyager

National_Geographic

A new interactive posting from National Geographic tells the story of the twin Voyager spacecraft, sent to explore the outer planets and the edge of our Solar System.

Links: The Voyager feature on the National Geographic website; a short movie.

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From a JPL press release, August 21, 2014:

NASA’s Voyager 2 spacecraft gave humanity its first close-up look at Neptune and its moon Triton in the summer of 1989. Like an old film, Voyager’s historic footage of Triton has been “restored” and used to construct the best-ever global color map of this strange moon. The map, produced by Paul Schenk, a scientist at the Lunar and Planetary Institute in Houston, has also been used to make a movie recreating that historic Voyager encounter, which took place 25 years ago, on August 25, 1989. (See pp. 190-192)

Map of Triton

Credit: NASA/JPL-Caltech/Lunar & Planetary Institute

The new Triton map has a resolution of 1,970 feet (600 meters) per pixel. The colors have been enhanced to bring out contrast but are a close approximation to Triton’s natural colors. Voyager’s “eyes” saw in colors slightly different from human eyes, and this map was produced using orange, green and blue filter images.

In 1989, most of the northern hemisphere was in darkness and unseen by Voyager. Because of the speed of Voyager’s visit and the slow rotation of Triton, only one hemisphere was seen clearly at close distance. The rest of the surface was either in darkness or seen as blurry markings.

The production of the new Triton map was inspired by anticipation of NASA’s New Horizons encounter with Pluto, coming up a little under a year from now. Among the improvements on the map are updates to the accuracy of feature locations, sharpening of feature details by removing some of the blurring effects of the camera, and improved color processing.

Although Triton is a moon of a planet and Pluto is a dwarf planet, Triton serves as a preview of sorts for the upcoming Pluto encounter. Although both bodies originated in the outer solar system, Triton was captured by Neptune and has undergone a radically different thermal history than Pluto. Tidal heating has likely melted the interior of Triton, producing the volcanoes, fractures and other geological features that Voyager saw on that bitterly cold, icy surface.

Pluto is unlikely to be a copy of Triton, but some of the same types of features may be present. Triton is slightly larger than Pluto, has a very similar internal density and bulk composition, and has the same low-temperature volatiles frozen on its surface. The surface composition of both bodies includes carbon monoxide, carbon dioxide, methane and nitrogen ices.

Voyager also discovered atmospheric plumes on Triton, making it one of the known active bodies in the outer Solar System, along with objects such as Jupiter’s moon Io and Saturn’s moon Enceladus. Scientists will be looking at Pluto next year to see if it will join this list. They will also be looking to see how Pluto and Triton compare and contrast, and how their different histories have shaped the surfaces we see.

Links: the full JPL press release; Triton movie.

More than 400 years after its discovery by Italian astronomer Galileo Galilei (see Figure 3-2, p. 38), the largest moon in the Solar System – Jupiter’s moon Ganymede – has finally been fully mapped (see Section 7.1g(iii), pp. 175–176). Since its discovery in January 1610, Ganymede has been the focus of repeated observation, first by Earth-based telescopes, and later by the flyby missions and spacecraft orbiting Jupiter. These studies depict a complex, icy world whose surface is characterized by the striking contrast between its two major terrain types: the dark, very old, highly cratered regions, and the lighter, somewhat younger (but still very old) regions marked with an extensive array of grooves and ridges.

Credit: USGS Astrogeology Science Center/Wheaton/NASA/JPL-Caltech

Scientists have now produced the first global geologic map of Ganymede, Jupiter’s seventh moon. The map combines the best images obtained during flybys conducted by NASA’s Voyager 1 and 2 spacecraft (1979) and Galileo orbiter (1995–2003) and is now published by the U.S. Geological Survey as a global map. It technically illustrates the incredibly varied geologic character of Ganymede’s surface and helps planetary scientists to make sense of the apparent chaos of its complex surface, in order to decipher the icy world’s evolution. It will also enable researchers to compare the geologic characters of other icy satellite moons in the Solar System.

The European Space Agency’s Jupiter Icy Moons Explorer mission is slated to be orbiting Ganymede around 2032, with instrument contributions from NASA.

Earth-bound astronomers can observe Ganymede (with binoculars) in the evening sky this month, as Jupiter is in opposition and easily visible.

Links: JPL press release; a rotating Ganymede movie; the geologic map.

NASA’s Voyager 1 spacecraft is officially the first human-made object to venture into interstellar space. The 36-year-old probe is about 12 billion miles (19 billion kilometers) from the Sun.

PIA17462_ip

Credit: NASA/JPL-Caltech

New and unexpected data indicate Voyager 1 has been traveling for about one year through plasma, or ionized gas, present in the space between stars. Voyager is in a transitional region immediately outside the solar bubble, where some effects from our sun are still evident. A report on the analysis of this new data, led by Don Gurnett and the plasma wave science team at the University of Iowa, Iowa City, is published in the journal Science.

Voyager 1 does not have a working plasma sensor, so scientists needed a different way to measure the spacecraft’s plasma environment to make a definitive determination of its location. A coronal mass ejection, a massive burst of solar wind and magnetic fields, that erupted from the Sun in March 2012 provided scientists with the data they needed. When this blast from the Sun eventually overtook Voyager 1 some 13 months later, in April 2013, the plasma around the spacecraft began to vibrate like a violin string. On April 9, Voyager 1’s plasma wave instrument detected the movement. The pitch of the oscillations helped scientists determine the density of the plasma. The particular oscillations meant the spacecraft was bathed in plasma more than 40 times denser than what they had encountered in the outer layer of the heliosphere. This density is that which is expected in interstellar space.

Much more information is available on NASA’s Voyager page, and via this JPL press release, which includes more images and a short video. The sound of interstellar space may be heard here.