Saturday, November 22, 2014

Europa Remastered

The puzzling, fascinating surface of Jupiter's icy moon Europa looms large in this newly-reprocessed color view, made from images taken by NASA's Galileo spacecraft in the late 1990s. This is the color view of Europa from Galileo that shows the largest portion of the moon's surface at the highest resolution.

The view was previously released as a mosaic with lower resolution and strongly enhanced color (see PIA02590). To create this new version, the images were assembled into a realistic color view of the surface that approximates how Europa would appear to the human eye.

The scene shows the stunning diversity of Europa's surface geology. Long, linear cracks and ridges crisscross the surface, interrupted by regions of disrupted terrain where the surface ice crust has been broken up and re-frozen into new patterns.

Color variations across the surface are associated with differences in geologic feature type and location. For example, areas that appear blue or white contain relatively pure water ice, while reddish and brownish areas include non-ice components in higher concentrations. The polar regions, visible at the left and right of this view, are noticeably bluer than the more equatorial latitudes, which look more white. This color variation is thought to be due to differences in ice grain size in the two locations.

Images taken through near-infrared, green and violet filters have been combined to produce this view. The images have been corrected for light scattered outside of the image, to provide a color correction that is calibrated by wavelength. Gaps in the images have been filled with simulated color based on the color of nearby surface areas with similar terrain types.

This global color view consists of images acquired by the Galileo Solid-State Imaging (SSI) experiment on the spacecraft's first and fourteenth orbits through the Jupiter system, in 1995 and 1998, respectively. Image scale is 1 mile (1.6 kilometers) per pixel. North on Europa is at right.

Image credit: NASA/JPL-Caltech/SETI Institute

Note: For more information, see NASA Issues 'Remastered' View of Jupiter's Moon Europa.

Tuesday, September 9, 2014

Plate Tectonics on Europa

Scientists have found evidence of plate tectonics on Jupiter's moon Europa. This conceptual illustration of the subduction process (where one plate is forced under another) shows how a cold, brittle, outer portion of Europa's 20-30 kilometer-thick (roughly 10-20 mile) ice shell moved into the warmer shell interior and was ultimately subsumed. A low-relief subsumption band was created at the surface in the overriding plate, alongside which cryolavas may have erupted.

Illustration credit: NASA/Noah Kroese, I.NK

Note: For more information, see Scientists Find Evidence of 'Diving' Tectonic Plates on Europa.

Tuesday, August 5, 2014

Three Massive Eruptions on Io

Jupiter's moon Io saw three massive volcanic eruptions within a two-week period last August. This August 29, 2013, outburst on Io was among the largest ever observed on the most volcanically active body in the solar system. The infrared was image taken by Gemini North telescope, courtesy of Katherine de Kleer, UC Berkeley.

Image credit: NSF/NASA/JPL-Caltech//UC Berkeley/Gemini Observatory

Note: For more information, see PIA18656: Eruptions on Io and A Hellacious Two Weeks on Jupiter's Moon Io.

Wednesday, July 9, 2014

Reddish Bands on Europa

This colorized image of Europa is a product of clear-filter grayscale data from one orbit of NASA's Galileo spacecraft, combined with lower-resolution color data taken on a different orbit. The blue-white terrains indicate relatively pure water ice, whereas the reddish areas contain water ice mixed with hydrated salts, potentially magnesium sulfate or sulfuric acid. The reddish material is associated with the broad band in the center of the image, as well as some of the narrower bands, ridges, and disrupted chaos-type features. It is possible that these surface features may have communicated with a global subsurface ocean layer during or after their formation.

Part of the terrain in this previously unreleased color view is seen in the monochrome image, PIA01125.

The image area measures approximately 101 by 103 miles (163 km by 167 km). The grayscale images were obtained on November 6, 1997, during the Galileo spacecraft's 11th orbit of Jupiter, when the spacecraft was approximately 13,237 miles (21,700 kilometers) from Europa. These images were then combined with lower-resolution color data obtained in 1998, during the spacecraft's 14th orbit of Jupiter, when the spacecraft was 89,000 miles (143,000 km) from Europa.

Image credit: NASA/JPL-Caltech/SETI Institute

Friday, May 16, 2014

Jupiter and Its Not-So-Great Red Spot

Jupiter's Great Red Spot is a churning anticyclonic storm. It shows up in images of the giant planet as a conspicuous deep red eye embedded in swirling layers of pale yellow, orange and white. Winds inside this Jovian storm rage at immense speeds, reaching several hundreds of kilometers per hour.

Historic observations as far back as the late 1800s gauged this turbulent spot to span about 41 000 kilometers at its widest point – wide enough to fit three Earths comfortably side by side. In 1979 and 1980 the NASA Voyager fly-bys measured the spot at a shrunken 23,335 kilometers across. Now, Hubble has spied this feature to be smaller than ever before.

This full-disc image of Jupiter was taken on 21 April 2014 with Hubble's Wide Field Camera 3 (WFC3).

Image credit: NASA, ESA, and A. Simon (Goddard Space Flight Center)

Note: For more information, see The Shrinking of Jupiter's Great Red Spot, Jupiter's Great Red Spot is Smaller Than Ever Measured, and Jupiter's Great Red Spot is Shrinking.

Friday, May 2, 2014

Ganymede's Possible Internal Structure

This artist's concept of Jupiter's moon Ganymede, the largest moon in the solar system, illustrates the "club sandwich" model of its interior oceans. Scientists suspect Ganymede has a massive ocean under an icy crust. In fact, Ganymede's oceans may have 25 times the volume of those on Earth. Previous models of the moon showed the moon's ocean sandwiched between a top and bottom later of ice. A new model, based on experiments in the laboratory that simulate salty seas, shows that the ocean and ice may be stacked up in multiple layers, more like a club sandwich.

Ice comes in different forms depending on pressures. "Ice I," the least dense form of ice, is what floats in your chilled beverages. As pressures increase, ice molecules become more tightly packed and thus more dense. Because Ganymede's oceans are up to 500 miles (800 kilometers) deep, they would experience more pressure than Earth's oceans. The deepest and most dense form of ice thought to exist on Ganymede is called "Ice VI."

When researchers added in salt into their models of the ocean, they found the situation changed from what was previously thought. With enough salt, liquid in Ganymede can become dense enough to sink to the very bottom of the seafloor, below Ice VI. Their models also suggest a complex stacking of ocean and ice, as illustrated in the picture.

What's more, the model shows that a strange phenomenon might occur in the uppermost liquid layer, where ice floats upward. In this scenario, cold plumes cause Ice III to form. As the ice forms, salt precipitates out. The salt then sinks down while the ice "snows" upward. Eventually, this ice would melt, resulting in a slushy layer in Ganymede's club sandwich structure.

Scientists say this structure may not be stable. It's possible the moon goes through a club sandwich phase, while at other times goes back to being more like a regular sandwich, with one ocean sitting below the familiar Ice I found on Earth and on top of different high-pressure ices.

The fact that salty water may persist at the bottom of the rocky seafloor, rather than ice, is favorable for the development of life. Researchers think life emerges through a series of chemical interactions at water-mineral interfaces, so a wet seafloor on Ganymede might be a key ingredient for life there.

Illustration credit: NASA/JPL-Caltech

Note: For more information, see Ganymede May Harbor 'Club Sandwich' of Oceans and Ice.

Thursday, February 27, 2014

Source Region for Possible Europa Plumes

This reprojection of the official USGS Europa basemap is centered at the estimated source region for potential plumes that might have been detected using the Hubble Space Telescope. The view is centered at -65 degrees latitude, 183 degrees longitude.

In addition to the plume source region, the image also shows the hemisphere of Europa that might be affected by plume deposits. This map is composed of images from NASA's Galileo and Voyager missions. The black region near the south pole results from gaps in imaging coverage.

Image credit: NASA/JPL-Caltech/SETI Institute