Outer Planets

The Outer Planets are Jupiter, Saturn, Uranus, and Neptune.  The following Table indicates the spacecraft that have been sent to the planets, the most recent is at the top of the list.  More information on each planet is given below…..

Jupiter Saturn Uranus Neptune
space craft successfully sent to the Planets;
New Horizons

Cassini

Ulysses

Galileo

Voyager 2

Voyager 1

Pioneer 11

Pioneer 10

Cassini-Huygens

Voyager 2

Voyager 1

Pioneer

Voyager 2 Voyager 2
USA (NASA)  European Space Agency China India Japan Russia

Jupiter

Description

 

Gas giant.  The largest planet in our solar system.  The visible clouds are mostly ammonia.  The atmosphere is mostly hydrogen and helium and extends down to a point where the pressure forms liquid hydrogen.  At a depth about two-third’s of the radius,  the liquid hydrogen becomes metallic due to the high atmospheric pressure.  At the center there is thought to be a rock-ice core about the size of earth.

Jupiter has 49 officially named Moons and many more identified with a number only. The four largest moons are planet sized and were discovered by Galileo with his small primitive telescope.  These moons are shown in the photo in this order:

Io – most volcanically active body in the solar system with an atmosphere of sulfur dioxide.  No water present.  Third largest of Jupiter’s satellites.  262,000 miles from Jupiter.
Europa – size of our moon, covered with an ocean of salty water with it’s surface frozen.  It has an atmosphere of oxygen.  It could support simple life forms.  420,000 miles from Jupiter.
Ganymede – The largest moon in the solar System.  It may have a liquid water ocean beneath it’s crust of water ice and rocks.  It may also have a thin oxygen atmosphere.  625,000 miles from Jupiter.
Callisto – Many Impact craters. No volcanoes and no geologic activity.  It is a dead planet, thought to have the oldest landscape in the solar system….4 million years old..  Second largest of Jupiter’s satellites.  1,170,000 miles from Jupiter.

Imagine for a moment that you were on Io at night, when Io was between the Sun and Jupiter.  Since Jupiter is so large, and Io is so close to Jupiter, you can imagine that Jupiter would fill the night sky and reflect a great deal of light!

Weather

It’s very interesting to think of how to describe the weather on Jupiter.  If you were standing on the rocky core, you’d be encased in metallic hydrogen….I suppose that would qualify for no weather at all!  If on the other hand you were above the metallic hydrogen and the liquid hydrogen, it would be windy, rainy (liquid hydrogen), and very cold.  If you were higher in the ammonia clouds you would experience very high winds.  It would be cold.  The good news is there would be no dust and no dirt!

Viewing

Jupiter can be easily seen with the naked eye.  The moons of Jupiter can be seen with a small telescope.

Visitors

(Names in Bold are still operational, strikethrough were not successful, blue are future.)

Europa Astrobiology Lander.  Proposed for 2036 to land on the moon Europa.
Juno.  In development for 2016.  This space craft will study the gravity field, magnetic field and atmosphere of Jupiter.
Prometheus One.  Proposed for 2015.  To orbit three of Jupiter’s moons
New Horizons – February 27, 2007.  Single fly-by.  Photos of Callisto.
Cassini-Huygens –  2000.  Single fly-by.  Continued on to orbit Saturn.
Ulysses – February 8, 1992.  ESA. Made 3 passes (Flybys)  studying the atmosphere and fields of Jupiter. Continued on to orbit the Sun.
Galileo – December 7, 1995.  Mapping and atmospheric measurements.  Released a probe to study the atmosphere, which lasted 58 minutes as it was consumed by the high pressures, intense radiation, and high winds.  At the end of its mission in 2003, the space craft was intentionally crashed into Jupiter.
Voyager 2 – July 9, 1979.  Images of Io, Europe, and Ganymede. Headed for Interstellar space via Saturn.
Voyager 1 – March 5, 1979.  Single fly-by.  Headed for Interstellar space via Saturn.
Pioneer 11 – December 2, 1974.  Single fly-by to take photos, atmospheric measurements.  Contact lost in 1995.
Pioneer 10 – December 3, 1973.  Single fly-by to take photos and magnetosphere measurements.  Continues the mission to exit the solar system.

Saturn

Description

Gas giant.  Atmosphere is 97% Hydrogen and 3% helium

Saturn has 52 moons with Titan being the largest.  Titan’s atmosphere is dominated by Nitrogen, similar to Earth,  Earth is 78% N2 while Titan is 95% N2. Although much smaller than Earth, Titan’s atmospheric pressure is about 50% greater than Earth.  The temperature is around -290oF.  Frozen water forms the land and liquid ethane and methane form the  lakes, rivers, and rain……a strange land indeed.

 

 

 

 

Weather

Saturn

Viewing

 

Visitors

(Names in Bold are still operational, strikethrough were not successful, blue are future.)

Future Flybys to be launched in 2015 will include several probes to be released into the planets atmosphere.
Cassini-Huygens.  Inserted into Saturn orbit on July 1, 2004.  The Huygens probe was released on December 24, 2004 in the vicinity of the moon Titan and landed on Titan 2 weeks  later on January 14, 2005.  The spacecrafts orbit brings it in close proximity to the moons of Saturn where it is able to make measurements of the atmosphere and surface of the moons.
Voyager 2.  August 26, 1981 Flyby with the closest approach to Saturn at 62,000 miles above Saturn.  It took photos of Saturn and several of its moons before departing to Uranus.  It currently is traveling toward interstellar space and is continues to be operational.
Voyager 1.  November 11, 1980 Flyby with the closest approach to Saturn at 77,000 miles.  Voyager 1 took hi-resolution photos of Saturn and its Moon Titan.  It currently is traveling toward interstellar space and is continues to be operational.
Pioneer 11.  First spacecraft to visit Saturn.  September 1, 1979 Flyby.  Pioneer 11 took photos of Saturn and then continued on to eventually leave the solar System.  All contact with the spacecraft was lost in November 1995, however the craft continues to travel towards interstellar space.

 

Uranus

Description

Uranus is very odd planet in that it spins on it’s side relative to its orbit around the Sun.   It is a true Gas giant in that there is no solid rocky core, however it does have a condensed liquid core made up of water, ammonia, and methane.   The atmosphere consists of hydrogen and helium, as well as methane and traces of water and ammonia.  It’s blue-green color comes from the methane in the atmosphere.

Uranus has 27 known moons and 11 rings.

 

 

 

 

Weather

Cold and dark.  The surface is covered with liquid so you will need a flotation device

Viewing

 

Visitors

(Names in Bold are still operational, strikethrough were not successful.)

Voyager 2.  January 24, 1986.  Single Flyby to study atmosphere and the magnetic field.

 

Neptune

Description

Named after the Roman God of the Sea.   Atmosphere of hydrogen and methane. Neptune also has rings consisting of small rocks and ice.  It is thought that Neptune has an earth-sized rocky core covered with water and other melted ices from the atmosphere. The deep blue color is due to methane and another element which currently remains a mystery.

Neptune has 13 moons including Triton, the largest of Neptune’s moons and one of just a few moons in the Solar System which has active geysers.

 

 

 

 

Weather

Cold and dark.  Sustained winds can be a couple hundred miles per hour.  If you are on the surface you will need a boat as the surface is covered with liquid water, hydrogen, and methane

Viewing

Too small to see with the unaided eye.

Visitors

Only 1 visitor to Neptune…

Voyager 2 – August 24, 1989.  Single fly-by.  Measured physical characteristics of Neptune and its moon Triton.  Continued on to interstellar space.

No current or future missions in development.

Pluto

Description

Way too cold.  Sorry, not a regular planet anymore.  It is the first object to be classified as a Dwarf Planet, a new category.  It is the smallest of the planets, having a diameter of just over 1400 miles….it would fit nicely in the Gluf of Mexico.

Pluto has 3 moons

Charon (KARE-on) approximayely half the size of Pluto
Nix – very small. Little is known of this moon
Hydra – very small.  Little is known of this moon.

 

 

 

Weather

Cold, no wind, no rain, no clouds….basically no weather, however it does have a very thin atmosphere discovered in 1988.

Viewing

Impossible to see with the naked eye.

Visitors

New Horizons.  Currently enroute for arrival in  2016.  Single Flyby of 150 days