Io’s True Colors


io_truecolorJupiter’s moon Io is one of the weirdest in the Solar System. It’s bright yellow, and this picture is an attempt to show how Io would appear to the average human eye. Io’s colors derive from sulfur and molten silicate rock. The moon’s is constantly being refreshed by a system of active volcanoes. Tides caused by Jupiter’s gravity stretch Io, and the resulting friction greatly heats Io’s interior, causing molten rock to explode through the surface. Io’s volcanoes are so active that they are effectively turning the whole moon inside out. Some of Io’s volcanic lava is so hot it glows in the dark.

Image Credit: NASA

Planetary Rings


RingsThese belong to Jupiter, not Saturn. The ring system of Jupiter was imaged by the Galileo spacecraft in 1996. This image the west ansa (the edge of a ring system) of Jupiter’s main ring has a resolution of 24 km per pixel. Plotting the brightness of ring from the inner-most edge of the image to the outer-most through the thickest part of the ring, shows the “dips” in brightness caused by perturbations from satellites. Two small satellites, Adrastea and Metis, which are not seen in this image, orbit through the outer portion of the ansa much like the small moon that shepherd Saturn’s rings.

Image Credit: NASA

Under Construction


ioplus_galileo_960Jupiter’s moon Io’s surface is constantly under construction. Io holds the distinction of being the Solar System’s most volcanically active body; its weird surface is continuously remade by lava flows. This high resolution composite picture was put together from images taken by the Galileo spacecraft back in 1996. It shows the side of Io that always faces away from Jupiter. The picture has been processed to bring out the moon’s surface brightness and color variations and shows details small as 2.5 km across. There aren’t many impact craters on Io which suggests that the entire surface gets covered with new volcanic deposits more rapidly than craters are created. The likely energy source for the vulcanism is the changing gravitational tides caused by Jupiter and the other three Galilean moons (Callisto, Ganymede, and Europa) as Io orbits the massive planet. The tides would heat the interior of the moon and generate its sulfurous volcanic activity.

Image Credit: NASA

A Thunderstorm on Jupiter


Jupiter_thunderstormThis false-color picture of a thunderstorm near Jupiter’s Great Red Spot was taken by the Galileo spacecraft in June, 1996. “Near” on Jupiter means about 10,000 km. The white cloud in the center is a tall, thick cloud 1,000 km across, extending 25 km or so higher than most of the surrounding clouds. The cloud base extends off to the left and appears red in this picture.

Different wavelengths of light penetrates to different depths in Jupiter’s atmosphere before being reflected back by clouds. Red represents data taken with the 756 nm filter, a wavelength where Jupiter’s atmosphere allows the light to penetrate deeply. Green and blue represent data taken with the 727 and 889 nm filters where the gases in the atmosphere absorb strongly, so only high clouds can reflect the light. The green and blue areas show high clouds; the red areas show deep clouds.

This red color indicates that the cloud base is very deep in the atmosphere, about 50 kilometers below the surrounding clouds. Most of the features in Jupiter’s clouds are ammonia clouds at a pressure just less than Earth’s sea level pressure. On Jupiter, water is the only substance forming clouds deeper in the atmosphere where the pressure is about five times the Earth’s sea level pressure. The red base of this thunderstorm is so deep that it can only be a water cloud. In 1979, the Voyager spacecraft detected convective clouds of this type near the Great Red Spot, but their cameras could not allow the determination of the storms’ altitude.

7X9_EarthIt is thought that these storms are analogous to an Earth thunderstorm, with the cloud’s high, bright, white portion comparable to the anvil clouds we see on Earth. We can’t tell it the precipitation is rain or snow, but there are indications that storms on Jupiter have lightning in them. The greatest difference between this storm and thunderstorms on Earth is the scale. The anvil of this storm is 1,000 km across and 75 km high. Here on Earth, the largest anvils are 200 km across and 18 km high. The image covers an area approximately 9,000 by 7,000 km. The thumbnail on the left shows an area of similar size on the Earth.

Image Credits: NASA

Cracks in the Ice


europa_riftseuropa-mainJupiter’s icy moon Europa is crisscrossed with rifts in its surface.  Agenor Linea is an unusually bright, white band on Europa. The mosaic  of color images above yields a high resolution view of Agenor within lower resolution images of the surrounding area. The images were captured by the Galileo spacecraft in 1998 and have been used by planetary scientists and astronomers to try to understand the “geology” of Europa.

Image Credits: NASA

Triple Conjunction


tripleconjuntion2scaleWhile driving back home from Baltimore last night, my son and I saw a rare triple conjunction of the planets Mercury, Venus, and Jupiter in the early night sky. Last night’s show was the most compact arrangement of the planets, but they will be visible together all this week. Mercury and Venus will be a bit higher above the horizon at sunset each night even as Jupiter sinks lower. The picture on the left show the three planets to scale. Venus is the brightest object in the sky other than the Sun or Moon. It’s the planet nearest to Earth and, being closer to the Sun, brightly illuminated. Jupiter is the farthest of the three, but it’s large reflecting area makes up for the distance. Tiny Mercury is closest to the Sun, but reflects the least light to us of the three.

Image Credits: NASA

Water, Water, Everywhere:


Nor any drop to drink.Jupiter_water

Astronomers have finally found direct proof that almost all water present in Jupiter’s stratosphere, an intermediate atmospheric layer, was delivered by comet Shoemaker-Levy 9, which struck the planet in 1994. The findings are based on new data from the Herschel space observatory and reveal more water in Jupiter’s southern hemisphere, where the impacts occurred, than in the north. Herschel is a European Space Agency mission.

Jupiter_Shoemaker_LevyThe origin of water in the upper atmospheres of the solar system’s giant planets has been a hot topic among planetary astronomers since the late ’90s. Astronomers were quite surprised when water was found in the stratospheres of Jupiter, Saturn, Uranus and Neptune by ESA’s Infrared Space Observatory.

The composite photo at left was assembled from separate images of Jupiter and comet Shoemaker-Levy 9 taken by the Hubble Space Telescope in 1994.

Image Credits: Top, ESA. Left, NASA

Jupiter from Saturn


Jupiter_from_SaturnThis is Jupiter as seen from Saturn’s orbit by the Cassini spacecraft. Cassini‘s cameras were specially designed to photograph the nearby bodies in the Saturn system, but as this image demonstrates, the cameras are pretty good telescopes. At the time this picture was taken, the distance to Jupiter was more than 11 times the distance between Earth and the Sun, a range of around 1.8 billion kilometers from Jupiter, or slightly farther than the average Earth-Saturn distance. Scale in the original image was about 10,000 kilometers per pixel—the Earth would show up as a single pixel at that scale.

Images taken using red, green and blue spectral filters were combined to create this natural color picture. The picture was contrast enhanced and magnified by a factor of two and a half to enhance the visibility of cloud features on the planet.

Image Credit: NASA

Jupiter’s Rings


Saturn’s rings are so prominent that they can be seen through a small telescope from Earth, but the other gas giant planets, Jupiter, Uranus, and Neptune, have ring systems as well. Jupiter's Rings

Jupiter’s rings were discovered by Voyager 1 in a single image that was targeted specifically to search for a possible ring system. Voyager 2 was reprogrammed en route to take a more complete set of pictures. The image above is from that series. We now known that the system has three major components. The Main ring is about 7,000 km wide and has an abrupt outer boundary roughly 129,000 km from the center of the planet. This ring encompasses the orbits of two small moons, Adrastea and Metis, which probably are the source for the material that makes up most of the ring. The main ring merges gradually into the Halo on the side toward Jupiter. The halo is a broad, faint, donut of material about 20,000 km thick and extending halfway from the main ring down to the planet’s cloudtops.

Around the main ring is the broad and exceedingly faint Gossamer ring. It extends out beyond the orbit of the moon Amalthea and is probably composed of dust particles less than 10 µm in diameter. That’s roughly the size of cigarette smoke particles. It extends to an outer edge of about 129,000 km from the center of the planet and inward to about 30,000 km. The origin of the ring is probably material knocked loose by micrometeorite bombardment of the tiny moons orbiting within the ring.

Jupiter’s rings and moons exist within an intense radiation belt of electrons and ions trapped in the planet’s magnetic field. These particles and fields make up the Jovian magnetosphere or magnetic environment which extends up to 7 million km toward the Sun and stretches outward 750 million km in a windsock shape to Saturn’s orbit.

Image Credit: NASA

Giant Spotted Planets


jupiter_red_spotOne of the most recognizable features in the Solar System is Jupiter’s Red Spot. However, Jupiter is not the only spotted planet. Neptune has long-term storm systems known as the dark spots. Voyager 2 made a close up picture of a Great Dark Spot when it flew by Neptune in 1989.

Based on observations taken by Voyager and with the Hubble Space Telescope, Neptune appears to have a Great Dark Spot more often than not. The Great Dark Spot is thought to be a hole in the methane cloud deck of Neptune. nepture_dark spot.

Neptune’s Great Dark Spot generates large white clouds at or just below the tropopause layer of the planet’s atmosphere similar to high-altitude cirrus clouds found on Earth. However, Neptune’s cirrus clouds are made up of crystals of frozen methane instead of water ice.

Image Credits: NASA

A Volcano on a Moon of Jupiter


io_lokiLoki Patera is the largest volcanic depression on Jupiter’s moon Io, 202 km in diameter. It contains an active lava lake, with an episodically overturning crust. Voyager 1 took this composite picture of Io showing an active plume from Loki on the moon’s limb. The images that make up this mosaic were taken from an average distance of approximately 490,000 km.

Image Credit: NASA

Jupiter and Ganymede


jupiterganymede_hstOne common observation made by amateur astronomers is watching Jupiter and it’s four large moons, the Galilean satellites Ganymede, Io, Europa, and Callisto. The satellites move quite noticeably over a one night’s viewing, and all that is required is a decent pair of binoculars (although the moons simply appear as points of light with low magnification).

Of course, if you have access to a good telescope, you can see more detail. This picture of Jupiter and Ganymede was made using the Hubble Space Telescope just as the moon was being eclipsed. Even some surface details of the moon can be seen.

Image Credit: NASA

Crescent Jupiter


We can’t see Jupiter like this from Earth. Because Jupiter is farther from the Sun than the Earth, it is always fully illuminated from our point of view. This picture was assembled from three color-filtered images taken by Voyager 1 on 24 March, 1979, as it flew past the planet. Click on the image to embiggen.

Image Credit: NASA/JPL

Triple Eclipse


This false-color image Jupiter shows a triple eclipse in progress on 28 March, 2004—a relatively rare event, even for a large planet with so many moons. This picture was taken by the Hubble Space Telescope’s near-infrared camera and show shadows of Jupiter’s moons Ganymede (left edge), Callisto (right edge) and Io as three dark spots on the Jovian cloud tops. Io itself is visible as a white spot near picture center, and Ganymede appears as a blue spot above Io and to the right. Callisto out of the frame to the right. From Jupiter these shadow crossings would be seen as solar eclipses just as our Moon’s shadow crossing the sunlit face of planet Earth. In 1676, timing the eclipses of Jupiter’s moons allowed astronomer Ole Roemer to make the first reasonably accurate measurement of the speed of light.

Image Credit: NASA

This Isn’t Saturn


Saturn isn’t the only planet with a ring system. This mosaic of Jupiter’s ring system was created with images taken by NASA’s Galileo spacecraft when the Sun was behind the planet. The spacecraft was in Jupiter’s shadow looking back toward the Sun. With such backlighting, very small dust-sized particles are highlighted so both the ring particles and the smallest particles in the upper atmosphere of Jupiter are visible.

Jupiter’s ring system is composed of three parts: a flat main ring, a toroidal halo between the main ring and the planet, and the gossamer ring, which lies outside the main ring. Only the main ring and a hint of the surrounding halo can be seen in this picture.

This composite of two mosaics was taken on 9 November, 1996, during Galileo’s third orbit of Jupiter. The ring was approximately 2.3 million kilometers away. Because the spacecraft was only about 0.5 degree above the ring plane, the image is highly foreshortened in the vertical direction. The vertical bright arcs in the middle of the ring mosaics show the edges of Jupiter and are composed of images obtained by NASA’s Voyager spacecraft in 1979.

Image Credit: NASA