Iapetus, moon of Saturn, discovered 1671

Iapetus, the third largest moon of Saturn, was discovered by Giovanni Cassini, October 25, 1671.  It is unique for several reasons.  First, it has a dark region, known as Cassini Regio, which is contrasted with the brightness from ice on the rest of the moon.  Ice covers most of the moon.

Second, Iapetus has an inclined orbit, more than any of the regular, i.e. largest, moons.  The rings of Saturn would be clearly visible because of its inclined orbit.  

Third, it has an equatorial ridge that runs through the center of  Cassini Regio.  Mountains in this ridge rise over 12 miles of the surrounding plains, making them among the tallest mountains in the solar system.  Mons Olympus on Mars is the tallest in the solar system. 

The source of the dark material and why the equatorial ridge exists only in Cassini Regio are unknown.

The spacecraft Cassini passed by at a range of 1,227 km (762 miles) on September 10, 2007. 

Huygens probe lands on Saturn's moon Titan 2005

The Huygens space probe, the atmospheric entry lander of the Cassini-Huygens mission, landed on Saturn's moon, Titan, January 14, 2005.  It was the farthest landing of any spacecraft and the first landing on Titan. Built and operated by the European Space Agency, the spacecraft was launched August 1997.

It sent data for about 90 minutes after landing.

Cassini-Huygens probe launched 1997

A storm in the northern hemisphere photographed by Cassini in 2011.

The Cassini-Huygens spacecraft, launched October 15, 1997, was a collaboration between NASA, the European Space Agency and the Italian Space Agency. Cassini was the fourth space probe to encounter Saturn but the first to enter into orbit. 

The Cassini probe was named after Giovanni Cassini, an Italian astronomer who discovered four of Saturn's moons and noted the separation of her rings.

The lander Huygens lander was named after Dutch astronomer Christiaan Huygens, who discovered Titan and is noted for his studies of Saturn's rings.

Cassini arrived in July 2004 and spent the next 13 years, far beyond its intended mission, studying the planet.  It was intentionally sent plunging into Saturn's atmosphere September 2017, to destroy it, preventing it from contaminating other celestial bodies.

The lander Huygens descended to the surface of Titan January 2015.  It took the first pictures from the surface of another moon besides ours.

Farewell, Cassini, the little probe that could!

Just before 8am EDT today, Cassini, the spacecraft sent to study Saturn and her moons, sent her last signal.  She plunged into the Saturnian atmosphere to end a massively successful mission.  Launched October 15, 1997, she spent Cassini spent 7 years en route and arrived at Saturn in 2004.  For 13 years, she has explored the gas giant and released the Huygens probe from the ESA to land on Titan, a first for a celestial body in the outer solar system.

Cassini did flybys of Jupiter, our moon and Asteroid 2685 Masursky.  She discovered new moons Methone, Pallene, Polydeucesin, Daphnis, Anthe, Aegaeon and S/2009 S 1.  I'm sure they will find a better name for the last one.

She also performed flybys of moons Titan, Phoebe, Enceladus, Iapetus, Rhea, Hyperion and Dione.

Seventeen countries joined together in this effort.

Epimetheus, Saturn's moon, up close!

While the Cassini spacecraft prepares for her swan song and death dive into the Saturnian atmosphere, she is still orbiting the planet and taking pictures of everything.  In February, Cassini performed a flyby of the inner moon Saturn XI or Epimetheus.

The moon Janus was discovered in December 1966 by two separate astronomers and believed there to be only one moon.  In 1978, two more astronomers determined that 1966 observations were best explained by two distinct objects, sharing very similar orbits.  Voyager 1 confirmed this in 1980, so the two astronmers Stephen Larson and John Fountain are credited with Epimetheus' discovery.

Epimetheus is only about 70 miles in diameter which means it is too small to have an atmosphere or to be geologically active.  It has two named craters, Hilairea and Pollux, characters from Castor and Pollux of Greek mythology.

Pan, Saturn's moon, looks like a UFO

Pan, Saturn's small moon, was photographed back in 1980 by Voyager 2, but wasn't officially discovered until 1990 by Mark Showalter analyzing old pictures.  Recently, the Cassini spacecraft studying Saturn and its moons has sent back images showing the moon to look like a UFO.

The tiny moon is only 35km across and 23km wide, but it keeps the Encke Gap (within Saturn's A Ring) clear of ring particles.

Cassini sends back beautiful images of Saturnian moons

Tethys

Daphnis - the wave maker

Mimas - the Death Star

Pandora

Prometheus

For over 12 years, the Cassini spacecraft has been orbiting Saturn, studying its moons, its rings and its atmosphere.  It is sending back some beautiful pictures of Saturnian moons.  It is scheduled to be destroyed by sending it into Saturn's atmosphere to avoid contamination of the moons.  (Huygens didn't contaminate Titan?).

Rhea(lly) beautiful - Saturn's moon

 

The Cassini spacecraft, currently hanging out in Saturn's neighborhood, has sent back stunning images of the planet's second largest moon, Rhea.  Discovered December 23, 1672 by Giovanni Cassini, Rhea is named after the Titan Rhea, mother of the gods in 1846 by John Herschel (son of William Herschel).

The dazzling image above was taken June 3 and is a result of the water ice that covers most of the surface.

Rhea is 949 miles in diameter and the most heavily cratered of all of Saturn's moons.   In 2010, NASA discovered a thin atmosphere consisting of oxygen and carbon dioxide.

Rhea's horizon.

Cassini flies by Titan today

 

The Cassini spacecraft flies by Saturn's moon Titan today!  Instruments will determine the composition of Titan's atmosphere. NASA posted a video of a computer simulation of the flyby.

Dione and Saturn's rings

Saturn's moon, Dione, looks split in half by Saturn's rings in this picture taken by the Cassini spacecraft from 1.4 million miles away.  Turnus, a medium sized crater, can be seen just above the seemingly razor thin rings. 

Discovered by Giovanni Cassini (the astronomer for whom the spacecraft is named), Dione wasn't named until 1847 when John Herschel (son of William who discovered Uranus) suggested the name of the sisters and brothers of Cronus be used.

Dione is the 15th largest moon in our solar system.

http://www.nasa.gov/image-feature/jpl/pia18358/dione-divided

Cassini spacecraft taking hi-resolution pics of Saturn's moons

Atlas

 

This small moon is only 30 kilometers, or 19 miles across.  Atlas orbits Saturn in a region called the Roche Division, between the planet's A and F rings, at the outer edge of the main ring system. The outer A ring is seen at the bottom of this view.

 

 

Epimetheus

 

A little larger than Atlas, Epimetheus is 116 kilometers, or 72 miles across.

 

Prometheus

 

Prometheus, 86 kilometers, or 53 miles across, orbits Saturn just inside the F ring, seen at the top of the picture.

 

Tethys

 

Tethys (531km or 319 miles) is dwarfed by Saturn and its rings.  A crescent view like this is impossible to see from Earth.  Reflected light from the rings illuminate Tethys' northern hemisphere.

 

nasa.gov

 

 

 

Cassini dives into Enceladus' plume

Two days ago, the Cassini spacecraft completed its deepest dive ever toward Saturn's moon, Enceladus.  The probe passed over the south polar region at a distance of only 30 miles.  During the flyby it took samples of the plumes which have been observed on Enceladus for years.  It'll take several weeks to complete the analyses but it should give researchers some clues to the composition of the global ocean beneath the surface. 

On its next and final flyby in December, Cassini will measure the amount of heat coming from the moon's interior.  Enceladus could be a future target for exploration in search of habitable environments beyond Earth.

Cassini-Hugyens spacecraft launched in 1997

The Cassini-Huygens space probe, now circling Saturn and her moons and sending back tons of data, started its seven year trek on October 15, 1997.  It arrived at the planet in June 2004 for a four year mission, which it completed in 2008 however it is still going strong.  It has sent back hundreds of gigabytes of data on Saturn, Titan, Enceladus, Iapetus, Dione, Hyperion, Tethys and other moons.

Starting this week, Cassini will make three close encounters with Enceladus.  She will fly through the icy material continually erupting from the moon's surface.  A tricky maneuver, given the speed of the probe and what damage even a small particle can do.

Part of the mission was to deploy the Huygens lander on the surface of Titan.  It landed with little difficulty and transmitted about 90 minutes after touchdown.  Images show an orange surface covered with hydrocarbon-coated water ice pebbles.  The temperature was a balmy -179.35 °C!  It's the farthest surface landing from Earth.

Saturnine moon Enceladus has global subsurface ocean

 

For the past ten years, the scientists at NASA have been studying data from the Cassini space probe in orbit above Saturn.  Launched October 15, 1997, the orbiter named after Italian astronomer Giovanni Cassini, reached its destination in mid-2004.  Since then, the probe has been collecting and sending data on Saturn’s atmosphere and rings, Titan’s atmosphere, Iapetus and Enceladus.

Researchers noticed a slight wobble in Enceladus, the sixth largest moon, as it orbited Saturn.  According to Carolyn Porco, the scientist leading the exploration of Enceladus, members of her team looked for a libration, a “small, cylindrical, back and forth deviation from uniform rotation”. They found what they were looking for but only in the thin, outer ice shell.  This means the shell and the rocky core are separated by a liquid layer and it is global.  Had the core and the ice shell been connected, the wobble would have been much less.

Why isn’t this liquid layer frozen? 

Scientists noticed plumes rising from the surface of Enceladus as early as 2005 and subsequently discovered icy ‘material’ emerging from warm fractures near the south pole.  They suggest hydrothermal activity is occurring on the subsurface ocean floor.

However, the pull of Saturn’s gravity might be generating more heat within Enceladus, which could also explain why the liquid layer is not frozen.

On October 28, Cassini is scheduled to fly only 30 miles above the surface of Enceladus, its closest approach ever, through the plumes of icy material.  Perhaps it will confirm the presence of organic material, the building blocks of life.