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. 

Chiron, minor planet, discovered 1977

Chiron, a minor planet between Saturn and Uranus, was discovered November 1, 1977, by Charles Kowal.  It was the first of a class of objects known as centaurs, astral bodies orbiting between the asteroid belt and the Kuiper Belt.  

It also has a classification as a comet, 95P/Chiron.

It has a radius of about 107.8 + 5km and rotates about every 6 hours.  It orbits the sun about every 50.5 years.

In February 1988, it brightened by 75%, which is typical of comets but not asteroids.  In April 1989, it developed a cometary coma, and in 1993, it formed a tail.  

Happy birthday, Mark Hamill!

Mark Hamill, born September 25, 1951 in Oakland, California, is best known for his role as Luke Skywalker in the original Star Wars trilogy and the latest trilogy, starting with Star Wars: The Rise of Skywalker.

He has won three Saturns (Academy of Science Fiction, Fantasy & Horror Films) for Best Actor in The Empire Strikes Back, Return of the Jedi and The Last Jedi.

Voyager 1 launched 1977

Voyager 1, launched September 5, 1977, was the fist man-made object to cross into interstellar space.  It was launched 16 days after Voyager 2 and flew by Jupiter in March 1979.

It made a flyby of Saturn in November 1980, including an encounter with Titan.

NASA still receives signals from both Voyager craft, but Voyager 1 might run out of fuel by 2025.

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.

Pioneer 11 launched 1973

Pioneer 11, interplanetary probe, was launched by NASA April 6, 1973.  It studied the asteroid belt, Jupiter and Saturn.  Pioneer 11 passed through the asteroid belt in April 1974 and encountered Jupiter December 3, 1974.

It flew by Saturn September 1, 1979, becoming the first probe to encounter the planet. It passed beyond the orbit of the planets on February 23, 1990, making it the fourth man-made object to do so. The last meaningful data received was on November 24, 1995.  In 2002, its signal became too faint to detect.

Pioneer 10 launched 1972

Taking advantage of a rare alignment of the outer planets, NASA launched Pioneer 10 March 2, 1972.  NASA started preparing for the mission in 1964 and created two spacecraft, Pioneer F and Pioneer G.  Later they were renamed Pioneer 10 and Pioneer 11.

On November 8, 1973, Pioneer 10 crossed the orbit of Sinope, an outer moon of Jupiter and made its closest approach to the planet December 3.  The electron radiation around Jupiter caused false commands to be made but many were corrected by contingency commands.  An image of Io and some close-up pictures of Jupiter were lost but the spacecraft obtained pictures of Ganymede and Europa.

On its way out of the solar system, Pioneer 10 crossed the orbit of Saturn in 1976, the orbit of Uranus in 1979, and the orbit of Neptune in 1983.  It is the first spacecraft to leave the solar system.

The mission officially ended March 31, 1997 but the Deep Space Network kept track of its signal until January 23, 2003 when Pioneer 10 sent its last signal.

Chiron discovered 1977

Chiron, an asteroid/minor planet/comet/centaur/whatsit, was discovered by Charles Kowal November 1, 1977 from images taken October 18 from the Palomar Observatory in southern California.  It may have been observed as far back as 1895.

At first, Chiron (named after the wisest and justest centaur from Greek mythology) was classified as a minor planet because its orbit lay between Saturn and Uranus, much further than the asteroid belt.  Subsequently, its classification was downgraded to an asteroid. 

Then in 1988, it brightened by 75% which is characteristic of comets, but not asteroids.  In 1993, a tail was discovered so NASA thought it was a comet.  So they decided, why not classify it as both a comet and a minor planet.  Chiron is officially known as a centaur, a dual classification of comet and minor planet, orbiting between the asteroid belt and the Kuiper belt.




https://en.wikipedia.org/wiki/2060_Chiron

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.

Pioneer 11 encounters Saturn 1979

Launched April 6, 1973, Pioneer 11 became the first space probe to encounter Saturn on September 1, 1979.  It followed Pioneer 10 through the asteroid belt and past Jupiter, but then headed toward Saturn.  During its flyby, it discovered a new ring and almost collided with a new moon discovered the day before, Epimetheus.  After the Voyager flybys, it was discovered that Janus (already known moon) and Epimetheus occupy the same orbit and are about the same size, so it could have been either one.

On September 29, 1995, NASA announced it was closing the project after over 22 years.

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

 

 

 

Voyager 1 flies by Saturn in 1980

Voyager 1, the second spacecraft sent to study Saturn (the first being Pioneer 11), passed by the gas giant on November 12, 1980.  Launched on September 5, 1977 (my birthday!), it took advantage of a rare planetary alignment and used gravity to swing by one planet (Jupiter) to the next without a large propulsion system.

Voyager 1 found three new Saturnine moons (Prometheus, Pandora and Atlas), hundreds of new rings and a thick atmosphere on Titan.

In August 2012, Voyager entered interstellar space, making it the most distant human-made object in space.  It carries a gold record that contains 115 analog images, greetings in 55 languages, 35 natural and man-made sounds and portions of 27 musical pieces. 

Voyager 1 should operate until 2020 and send back data to Earth periodically.

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.