Io and Jupiter


In Greek mythology Io was a priestess of Hera (Zeus’ wife) and a nymph who was seduced by Zeus. He changed her into a heifer to escape detection. Io is also the name of the innermost of the four Galilean moons of the planet Jupiter. The most volcanic body in the Solar System, Io is 3,600 kilometers in diameter, about the size of planet Earth’s moon.

While cruising past Jupiter at the turn of the millennium, the Cassini spacecraft captured this view of Io with Jupiter as a backdrop–offering an impressive demonstration of the ruling planet’s relative size. (An astronomer from another star system would probably describe our solar system as having one main planet and assorted debris.) Although Io appears to be located just in front of the swirling Jovian clouds, Io is about 350,000 km above Jupiter’s cloud tops. That’s roughly the same as the distance between Earth and Moon. The Cassini spacecraft itself was about 10 million km from Jupiter when this picture was taken.

Image Credit: NASA

Herschel Crater


Herschel Crater is 130 km wide, covering a large portion of Saturn’s moon Mimas. The moon itself is only 396 km wide.

The dayside terrain seen here is on leading hemisphere of Mimas. North on Mimas is up and rotated 1 degree to the left in this image which was taken in visible light by the Cassini spacecraft in 2010.

Image Credit: NASA

You Can’t See It From Here


Crescent SaturnThis is a view of Saturn partially lit in crescent phase, a view that can only be seen when the object is between the observer and the Sun. From the Earth, we can only see Mercury and Venus in varying crescent phases and Mars and the other outer planets fully lit. Because the Moon can be either between the Earth and the Sun or farther away, we see it go through all the phases from New to Full to New again.

This picture of Saturn was made by the Cassini spacecraft.

As the data download from New Horizons proceeds, we should soon have pictures from an similar point of view of the Kuiper Belt Object Ultima Thule.

Image Credit: NASA

Moar Science from Cassini


As the Cassini spacecraft was running out of fuel for the thrusters used to maintain control of its attitude so that it could point it instruments at the desired targets and its antenna toward Earth so send back data, it was placed in a series of Grand Finale orbits that took it between Saturn’s rings and the planet’s upper atmosphere. Eventually, an orbit was low enough that the spacecraft burned up in the upper atmosphere. It will take years to go through all the data, but papers are beginning to be published with findings from the Grand Finale. Interesting findings include an electric current that flows between the rings and the upper atmosphere and organic compounds falling as “rain” from the rings. There’s more interesting stuff here. Go take a look.

Image Credit: NASA

The Dust Storms of Titan


Analysis of data taken by the Cassini spacecraft appears to show giant dust storms on Saturn’s moon Titan. Titian is the second largest moon in the Solar System (Jupiter’s moon Ganymede is slightly bigger.); it’s even lager than the planets Mercury and Pluto (Pluto is still a planet in the Hogewash! universe.). Titan is the only other body in the Solar System beside Earth that has stable surface liquid, hydrocarbons rather than water. If the dust storms are really occurring, it would join Earth and Mars as the only known bodies in the Solar System with dust storms.

The animation above is based on images captured by Cassini mission during several Titan flybys in 2009 and 2010. The bright spots that have been interpreted as evidence of the dust storms.

There’s more information about this at the NASA website.

Image Credit: NASA

Not a Solar Eclipse


titanbusy_cassini_960No, it’s not a solar eclipse. It’s a picture of the rings and a couple of the moons of Saturn. The large object near the center is Titan, Saturn’s largest moon and one of the most interesting objects in the entire Solar System. The central dark spot is the body of the moon. The bright halo is atmospheric haze above Titan. The gases of the atmosphere scatter sunlight. Saturn’s rings are shown nearly edge on. Enceladus, a small moon, is at about 4 or 5 o’clock at the edge of Titan.

This image was taken with the Cassini spacecraft’s camera pointing almost directly at the Sun, so the surfaces of Titan and Enceladus appear in silhouette, and the rings of Saturn look like a photographic negative.

Image Credit: NASA

You Can’t See This From Here


Crescent SaturnThis is a view of Saturn partially lit in crescent phase, a view that can only be seen when the object is between the observer and the Sun. From the Earth, we can only see Mercury and Venus in varying crescent phases and Mars and the other outer planets fully lit. Because the Moon can be either between the Earth and the Sun or farther away, we see it go through all the phases from New to Full to New again.

This picture of Saturn was made by the Cassini spacecraft.

Image Credit: NASA

Translucent Rings


Saturn’s rings are mostly water ice in chunks that range in size from smaller than a grain of sand to mountains. The ring system extends 282,000 km from the planet, but it’s only about 10 m thick in most places. Looking from some angles, it’s possible to see through the rings—as in this that looks from south to north. The Cassini spacecraft took the images stitched together in this natural-color mosaic in April, 2007, when it was about 725,000 kim from Saturn.

Image Credit: NASA

A Reflection from Titan


titan_lake_flashThis image shows a flash of sunlight reflected off a lake on Titan, Saturn’s largest moon. Its northern hemisphere is shrouded in darkness for nearly 15 years, but the sun begins to illuminate the area again as it approaches its spring equinox. The Cassini spacecraft was able to detect the glint at the beginning of Titan’s spring in 2009. The moon’s hazy atmosphere scatters and absorbs many wavelengths of light, including most of the visible spectrum. But an onboard instrument was able to detect the glint in infrared wavelengths that can penetrate through Titan’s atmosphere. This image was created using wavelengths of light in the 5 µm range.

Image Credit: NASA

Tuning in on Saturn


New research from the up-close Grand Finale orbits of the Cassini mission shows a surprisingly powerful interaction of plasma waves moving from Saturn to its moon Enceladus. The data used to make this video was captured by the Radio Plasma Wave Science (RPWS) instrument two weeks before Cassini was deliberately plunged into the atmosphere of Saturn.

Video Credit: NASA / JPL-Caltech / University of Iowa

Odysseus


Don’t worry. It’s a moon, not a space station.

It’s Saturn’s icy moon Tethys. The enormous impact created the crater is named Odysseus. The crater is about 450 km across surrounded by a ring of steep cliffs and and has a rang of mountains rising from its center. Tethys is only a bit over 1070 km in diameter.

This picture is a composite assembled from images taken in visible light with the Cassini spacecraft in 2015 when is was roughly 44,500 km from the moon.

Image Credit: NASA

Saturn, Rings, and Moons


Cassini snapped this picture with its narrow-angle camera. It shows Saturn and its rings seen here nearly edge on. The image also shows the moons Mimas (above the rings), tiny Janus (apparently almost in the rings), and Tethys (below the rings). “Above” and “below” the rings is a matter of perspective. All three moons and the rings orbit Saturn in roughly the same plane.

Image Credit: NASA

Enceladus, Pandora, and Rings (Oh, My!)


Saturn’s moon Enceladus is backlit by the Sun in this Cassini spacecraft image from 2009. The dramatic lighting shows of the plumes that continuously spew into space from the south pole of 500 km diameter moon. The icy plumes are likely fed by an ocean beneath the ice shell of Enceladus. They supply material directly to Saturn’s outer, tenuous E ring and make the surface of Enceladus as reflective as snow. Behind Enceladus, Saturn’s rings scatter sunlight toward Cassini. Beyond the rings, the night side of the 80 km diameter moon Pandora is faintly lit by light reflecting off of Saturn.

Image Credit: NASA