All the Water on Europa
Illustration Credit & Copyright: Kevin Hand (JPL/Caltech),
Jack Cook (Woods Hole Oceanographic Institution), Howard Perlman (USGS)

Explanation: How much of Jupiter’s moon Europa is made of water? A lot, actually. Based on the Galileo probe data acquired during its exploration of the Jovian system from 1995 to 2003, Europa possesses a deep, global ocean of liquid water beneath a layer of surface ice. The subsurface ocean plus ice layer could range from 80 to 170 kilometers in average depth. Adopting an estimate of 100 kilometers depth, if all the water on Europa were gathered into a ball it would have a radius of 877 kilometers. To scale, this intriguing illustration compares that hypothetical ball of all the water on Europa to the size of Europa itself (left) - and similarly to all the water on planet Earth. With a volume 2-3 times the volume of water in Earth’s oceans, the global ocean on Europa holds out a tantalizing destination in the search for extraterrestrial life in our solar system.

Jupiter’s icy moons are the focus of Europe’s next large science mission, ESA announced today.
 
The Jupiter Icy moons Explorer – JUICE – was selected over two other candidates: NGO, the New Gravitational wave Observatory, to hunt for gravitational waves, and ATHENA, the Advanced Telescope for High-Energy Astrophysics.

JUICE is the first Large-class mission chosen as part of ESA’s Cosmic Vision 2015-2025 programme.

It will be launched in 2022 from Europe’s spaceport in Kourou, French Guiana, on an Ariane 5, arriving at Jupiter in 2030 to spend at least three years making detailed observations.

Read more here.

Jupiter and the Moons of Earth
Image Credit & Copyright: Stefan Seip (TWAN)

Explanation: Planet Earth has many moons. Its largest artifical moon, the International Space Station, streaks through this lovely skyview with clouds in silhouette against the fading light of a sunset. Captured from Stuttgart, Germany last Sunday, the frame also includes Earth’s largest natural satellite 1.5 days after its New Moon phase. Just below and left of the young crescent is Jupiter, another bright celestial beacon hovering near the western horizon in early evening skies. Only briefly, as seen from the photographer’s location, Jupiter and these moons of Earth formed the remarkably close triple conjunction. Of course, Jupiter has many moons too. In fact, close inspection of the photo will reveal tiny pin pricks of light near the bright planet, large natural satellites of Jupiter known as Galilean moons.

Io: Moon Over Jupiter
Image Credit: Cassini Imaging Team, SSI, JPL, ESA, NASA

Explanation: How big is Jupiter’s moon Io? The most volcanic body in the Solar System, Io (usually pronounced “EYE-oh”) is 3,600 kilometers in diameter, about the size of planet Earth’s single large natural satellite. Gliding past Jupiter at the turn of the millennium, the Cassini spacecraft captured this awe inspiring view of active Io with the largest gas giant as a backdrop, offering a stunning demonstration of the ruling planet’s relative size. Although in the above picture Io appears to be located just in front of the swirling Jovian clouds, Io hurtles around its orbit once every 42 hours at a distance of 420,000 kilometers or so from the center of Jupiter. That puts Io nearly 350,000 kilometers above Jupiter’s cloud tops, roughly equivalent to the distance between Earth and Moon. The Cassini spacecraft itself was about 10 million kilometers from Jupiter when recording the image data.

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Gas Giants

Four of the outer planets in our solar system are known as gas giants. They are Jupiter, Saturn, Uranus, and Neptune. Gas giants are composed mainly of hydrogen and helium and are quite large in size. Jupiter, for example, is 1000 times larger than the Earth. Gas giants also have low densities and tend have a very fast period of rotation. All four of the gas giants in our solar system have ring systems and a large number of moons. This may be due to the intense gravity of these planets. They may have more of a tendency to capture wandering asteroids and planetoids then the terrestrial planets. It is believed that the ring systems may have formed from old moons that were pulverized by the tidal forces of the planets’ gravity.

Images Credit: solarsystem.nasa.gov

Paris by Night
Image Credit & Copyright: Serge Brunier (TWAN)

Explanation: Do you recognize the city lights of Paris in this picture? Taken on March 25 from the top of the 210 meter tall Montparnasse skyscraper, many will spot the looming Eiffel Tower, or the large domed structure of Les Invalides (right), or the colorfully lit elevated Metro train line gently curving toward picture center. You can even pick out the Arc de Triomphe close to the horizon on the right. But regardless of your location, the celestial lights near the western horizon should look very familiar. The lovely triple conjuntion of brilliant Venus (top), Jupiter, and a young crescent Moon was visible in evening skies around planet Earth.

The Grand Canyon in Moonlight
Image Credit & Copyright: Malcolm Park (North York Astronomical Association)

Explanation: In this alluring night skyscape recorded on March 26, a young Moon stands over the distant western horizon in conjunction with brilliant planet Venus. In the foreground, the Colorado River glistens in moonlight as it winds through the Grand Canyon, seen from the canyon’s southern rim at Lipan Point. Of course, the Grand Canyon is known as one of the wonders of planet Earth. Carved by the river, the enormous fissure is about 270 miles (440 kilometers) long, up to 18 miles (30 kilometers) wide and approaches 1 mile (1.6 kilometers) deep. On this date, wonders of the night sky included the compact Pleiades and V-shaped Hyades star clusters poised just above the Moon. Bright planet Jupiter is below the closer Moon/Venus pairing, near the western horizon.

Beautiful view of the Moon, Venus and Jupiter from my bedroom window :)

Bright Planets at McMath-Pierce Solar Telescope
Image Credit: Mike Line (Caltech), Ed Mierkiewicz (Univ. Wisconsin-Madison), Ron Oliversen (NASA-GSFC)

Explanation: Bright planets Venus and Jupiter are framed by the National Solar Observatory’s McMath-Pierce Solar Telescope in this very astronomical scene. The photo was taken at Kitt Peak National Observatory on March 9. A heliostat sits atop the 100 foot high solar telescope tower to focus the Sun’s rays down a long diagonal shaft that reaches underground to the telescope’s primary mirror. Of course, after sunset shadows were cast and the structure illuminated by light from the nearly full rising Moon. Opened to begin the night’s work, the dome housing Kitt Peak’s 2.1 meter reflector is included in the frame, while the Pleiades star cluster shines above the heliostat tower. The angular McMath-Pierce was commissioned 50 years ago to study the Sun, but has also made many observations of these two bright planets. On this night it was conducting observations of sodium atoms in the tenuous lunar atmosphere.