1. J o v i a n P
l a n e t s

2. Jovian Planets
All of the jovian planets were visited by the Voyager probes in the 1970s and 80s

3. Jovian Planets
None of the jovian planets have a solid surface of any kind – their gaseous surfaces just get hotter and more dense with depth due to pressure of the overlying layers, eventually becoming liquid in the interior.
Jupiter, Saturn and Neptune have significant internal heating which impacts the behavior and appearance of their atmosphere.

4. Jovian Planets
With no surface to tie down gas flow, the different parts of the atmosphere flow at different speeds – differential rotation.
On Jupiter, the equatorial regions rotate every 9h50m and higher regions take 6 min longer.
On Saturn the difference is 26 minutes, with equatorial rotating more rapidly.
On Uranus the difference is 2 hours with the poles rotating more rapidly
On Neptune, the difference is 6 hours, and again, the poles rotate more rapidly.

5. Jovian Planets
All jovian planets have strong magnetospheres and emit radiation at radio wavelengths.
The strength of the radio emissions varies with time and is periodic – assumed to match the rotation of the planets’ interior, where the magnetic field arises.
There is no apparent relationship between interior rotation rates and exterior rotation rates.

7. Jupiter
Jupiter is the 3rd brightest object in the night sky (after the Moon and Venus, respectively)
It is so massive, that there is a myth that it was actually a failed star...Could Jupiter Become a Star-
Using a small telescope one can see the Galilean moons of Jupiter and the striped gaseous surface

8. Jupiter - Atmosphere
Jupiter’s most striking features are it’s multicolored bands and the Great Red Spot.

9. Ganymede’s shadow in the GRS Credit Hubble, April 21, 2014

10. Jupiter - Atmosphere What causes the colors? We don’t know.
The most abundant gas in the atmosphere is atmospheric hydrogen (86%), then helium (almost 14%) and then trace amounts of atmospheric methane, ammonia, sulfur, phosphorous and water vapor – none of which can account for the many colors.
Water vapor & ammonia = white clouds, so….
Perhaps chemical process in the turbulent atmosphere causes them, powered by internal heat, solar UV, aurorae in the magnetosphere and lightening discharges

11. Jupiter - Atmosphere
The banded structure is believed to be caused by convection currents in the planet's atmosphere.
Lighter-colored zones alternate with darker belts that vary in intensity and latitude.
Voyager sensors indicated that the belts were areas of lower pressure (sinking) and zones areas of higher pressure(rising), but Cassini contradicted this and no resolution has been reached.

12. Jupiter -Atmosphere
Because of the rapid rotation, the high and low pressure systems wrap all the way around the planet.
There are strong east-west winds that lie under the bands, called the zonal flow.
There are at least 30 of these jet streams on Jupiter, with average speeds of about 300mph (482km/h).
The flow speed decreases toward the poles, and near the poles, where the flow disappears, the banding also disappears.

13. Jupiter - Weather
The Great Red Spot appears to be a hurricane that has raged on for hundreds of years – at least since we first saw the planet
There is another spot, Oval BA, discovered in 2008, which grew and then got eaten by the GRS.

14. Jupiter - Weather
The GRS rotates around the planet at a speed similar to the rotation of the planet's interior, so the storm must reach very deeply into the planet.
Alternating east and west zonal flows keep the GRS confined and give support to the idea that the storm is powered by Jupiter's massive atmospheric motion.
apodaca.nasa.gov 14

15. Jupiter - Weather
There are many other storms on the planet...some are colored by the cloud tops, and the "brown oval" is a hole in the overlying clouds.
jpl.nasa.gov 15
garybrandastrology.com

16. Jupiter - Weather
Perhaps spot color has to do with size and intensity of storm....smaller are white tipped, but the larger ones seem to turn red....possibly the cloud cover is lifted higher up where interaction with UV radiation causes chemical reactions changing the color.
Supporting evidence of this came from three small white spots that merged into one larger one, and turned red. 16

17. Jupiter Jupiter has rings!
In 1979, Voyager 1 was the first to send back photographic evidence of rings around Jupiter, and Voyager 2 was immediately programmed for a flyby to get a better look. 17

18. Jupiter
There are three ring systems: the innermost Halo Ring, the Main Ring and two Gossamer Rings.
The Main Ring is only visible when seen from behind Jupiter, looking back toward the Sun and lit by the Sun’s light.
Galileo confirmed that the Main Ring was made up from material from the moons Adrastea and Metis, mostly Adrastea, through meteor impacts.
The
composition of
Adrastea is
unknown. 18

19. Jupiter’s Ring
Solar radiation and collisions with charged particles trapped in Jupiter’s magnetic field exert a friction on the ring dust that will eventually cause the dust to drift into the atmosphere
To maintain the rings, new dust must be provided from the Jovian moons
Jupiter has a system of rings made of tiny particles of rock dust and held in orbit by Jupiter’s gravity

20. Internal Structure - Jupiter
Temperature and pressure increase with depth
At a depth of a few thousand kilometers, the gaseous atmosphere on Jupiter makes a gradual transition to liquid.
At around 20,000km, the pressure is about 3million x the atmospheric pressure on Earth, causing the liquid hydrogen to compress in a metallic state, with similar properties to liquid metals on Earth.
***Excellent conductor of electricity*** 20

21. Internal Structure - Jupiter
Jupiter’s equator has a bulge thanks to its rotation – he radius at the equator exceeds the poles by 7%
Calculations show that a composition of only hydrogen and helium should result in an even greater disparity than that….the core is indicated to be as much as 10x the mass of Earth.
Actual composition is obviously unknown but theorized to be composed of similar materials to the terrestrials – molten, maybe semisolid, rock.
Because of the incredible pressure, the core must be very compressed.

22. Internal Heating
With a core temperature of about 30,000K Jupiter emits about twice as much heat as it receives from the Sun….possibly excess energy left over from the planet’s formation.
In the past, Jupiter may have been much hotter than it is now and the heat is slowly leaking out.

23. Magnetospheres
Jupiter has the strongest magnetic field in the solar system thanks to its rapid rotation and extensive region of highly conduct
Jupiter’s magnetosphere is HUGE!
20,000 x Earth’s

24. Magnetospheres
Jupiter sends particles from its magnetosphere into its upper atmosphere forming aurorae much larger and more energetic than those that we experience on Earth,

25. Jupiter - Missions
Most of our detailed information we have on Jupiter comes from the space missions past and to the planets.
The two Voyager probes, launched, in 1977 reached Jupiter in March and July of 1979.
Sounds of Jupiter
Galileo launched in 1989 and arrived in 1995, needing gravity assists from Venus and Earth to reach Jupiter.
Mission was to study the atmosphere of Juipter and its moon system.
To end in 1997 but extended to 2003 when it was crashed into the surface.

26. Jupiter - Missions
Cassini was launched in 1997 to study Saturn, but spent 6 months viewing Jupiter during the first months of 2001.
Juno will reach Jupiter in 206 and will hopefully answer many questions regarding the Jovian planets.

27. The Moons of Jupiter Io
Europa
Ganymede
Callisto
Jupiter currently has 63 natural satellites or moons
Number changes frequently as more are discovered
Four innermost moons are called the Galilean Moons

28. The Moons of Jupiter Except for Europa, all are larger than the MoonIo
Europa
Ganymede
Callisto
Except for Europa, all are larger than the Moon
Formed in a process similar to the formation of the Solar System – the density of these satellites decreases with distance from Jupiter

29. Io
Gravitational tidal forces induced from Jupiter and Europa keeps Io’s interior hot
Volcanic plumes and lava flows are the result

30. Europa
Very few craters indicate interior heating by Jupiter and some radioactive decay
Surface looks like a cracked egg indicating a “flow” similar to glaciers on Earth
Heating may be enough to keep a layer of water melted below the crust

31. Ganymede and Callisto
Look like our Moon with grayish brown color and covered with craters
However, their surfaces are mostly ice – whitish craters a very good indication of this
Callisto may have subsurface liquid water
Ganymede is less cratered than Callisto indicating maria-type formations although tectonic movement cannot be ruled out

32. Other Observations Io
Europa
Ganymede
Callisto
Galilean average densities indicate their interiors to be composed mainly of rocky material
Differentiation may have allowed iron to sink to core
Rest of Jupiter’s moons are much smaller than the Galilean satellites and they are cratered
Outermost moons have orbits that have high inclinations suggesting that they are captured asteroids

33. Io – orbits every 1.8 days

34. Saturn
First close pass by Pioneer at 13,000 miles. Discovered the F-ring. Pioneer is still transmitting from somewhere toward the center of the Milky Way Galaxy.

35. Saturn
There are three cloud layers in Saturn’s atmosphere with an overall thickness about 3 times the thickness of Jupiter’s cloud cover…..and each cloud layer is thicker than its counterpart on Jupiter as well…..why?
The thicker clouds also result in fewer gaps and holes in the to layer so that we rarely see below to the more colorful levels below, which is why it appears so uniformly yellowish.

36. Saturn
Wind speed on Saturn is much faster than on Jupiter, reaching speeds of 932 mph (1500 km/s).
East-west zonal flow is stable, although there are fewer east/west alterations.
There are several storms on Saturn, but may simply be hidden under the upper cloud layers. Cassini has observed

37. Saturn
Storm Alley – this area of cyclonic rotation, where colder surface gases are drawn downward into the warmer interior only occurs in the southern hemisphere, not in the northern. Hmmm…..

38. Saturn
The hexagon surrounding a maelstrom at Saturn’s north pole is another puzzle – wind speeds reach 530 km/h inside and 500 km/h outside, butt the hexagon does not appear to move except with the planet’s rotation.

39. Picture from Cassini – from 605 million miles away

40. Saturn
Saturn’s dragon storm has remained in one location since 2004, with winds up to mph (1700 km/h)
Continues lightening flashes x more powerful than anything produced on Earth.
Seems to be rooted to a specific location on the surface – but why if there is no solid surface?
The radio emissions from the storms are so clock-like that they are used to judge the planet’s rotation rate below the clouds.

41. Seasons of Saturn

42. Internal Structure - Saturn
Saturn has the same internal structure, but different relative proportions from Jupiter.
Thinner metallic hydrogen layer
Thicker central core (inferred from greater polar flattening), about 15x the Earth’s mass
Saturn’s overall mass is much less than Jupiter’s, resulting in a much lower core temp, pressure and density – close to that of the center of Earth.

43. Internal Heating
Saturn also has an internal energy source – it radiates about 3x the energy it receives from the Sun.
Since it is smaller than Jupiter, it should have cooled more quickly, so the original heat supply should have been used up long ago….so why all the excess?

44. Internal Heating
Remember the lack of atmospheric helium (7% compared to 14% for the other jovians)?
At high temps & pressures (Jupiter), liquid helium dissolves in liquid hydrogen.
Saturn’s temps are lower, so helium does not dissolve as easily and instead forms droplets….it condenses out like rain does on Earth, sinking into the interior, compressing the gravitational field and heating it up.
When the helium rain stops, the core should cool and the amount of radiation it emits should equal out the radiation received from the Sun.

45. Magnetospheres
Saturn also has a strong magnetic field and magnetosphere.
Smaller mass of the metallic hydrogen zone results in much less strength at the cloud topss – 1/20 of Jupiter’s.
Contains the ring system and most of its moons.

46. Saturn - Cassini
Cassini launched in Sept 1997, and, after a 6 month visit to Jupiter at the first of 2001,entered orbit around Saturn in June 2004.
It will end its mission on Sept 15, 2017 by entering the atmosphere.
The Huygens probe was launched from Cassini and landed on the moon Titan in the winter of 2004/5 and sent back several pictures and data that is being analyzed.

47. The Rings of Saturn Rings are wide but thin
Main band extends from about 30,000 km above its atmosphere to about twice Saturn’s radius (136,000 km)
Faint rings can be seen closer to Saturn as well as farther away
Thickness of rings: a few hundred meters
Main band is made up of the visible A, B and C rings, from outside in

48. Ring Structure
Rings not solid, but made of a swarm of individual bodies
Sizes range from centimeters to meters
Composition mainly water, ice, and carbon compounds and is not uniform across rings

49. Ring Structure
Large gaps due to resonances with Saturn’s moons located beyond the rings
Narrow gaps due to complex interaction between ring particles and tiny moons in the rings

50. The rings of Saturn
The E Ring is formed from water ice droplets from the geysers on Enceladus and last until they strike another moon or get blown away from the planet.

51. The Phoebe Ring
Discovered when Iapetus (an icy, bright white moon) was observed moving through some substance that was causing the leading edge to turn dark.
Absorbs sunlight, but easily seen by infrared imaging with NASA’s WISE spacecraft, as above.

52. A & F Ring, Encke Gap with Titan in background…and tiny Epimetheus too
A & F Ring, Encke Gap with Titan in background…and tiny Epimetheus too! – Cassini,2014

53. The Roche Limit
Any object held together solely by gravity will break apart by tidal forces if it gets too close to the planet.
Distance of breakup is called the Roche limit and is 2.44 planetary radii, if object and planet have the same density
All planetary rings lie near their planet’s Roche limit… implying what?
Existence of side-by-side ringlets of different compositions indicates rings supplied by varied comets and asteroids
Objects bonded together chemically will survive Roche limit

54. The Roche Limit

55. Saturn’s Moons
Saturn has several large moons and many more smaller ones
Like Jupiter, most of the moons form a mini-solar system.
Saturn’s moons have a smaller density than those of Jupiter indicating interiors must be mostly ice
Most moons are inundated with craters, many of which are surrounded by white markings of shattered ice
The moons also have several surface features that have yet to be explained

56. Saturn’s Moons

57. Saturn Tethys the larger of the three Hyperion the the left
Prometheus, whose gravity helps define the edge of the F-ring 57

58. Surface of Enceledes, taken by Cassini, October 14, 2015

59. Enceledes, floating above Saturn’s Rings, Cassini, July 29, 2015

60. Prometheus

61. Titan Saturn’s largest moon Larger than Mercury
Mostly nitrogen atmosphere
Solid surface with liquid oceans of methane
The Huygens Probe landed on the surface

62. Images from Titan’s Surface

63. Dionne transiting Saturn

64. Uranus
Uranus was discovered in by William Herschel when he was mapping the stars with a 6” telescope.
First described as “a curious either nebulous star or perhaps a comet”

65. After George III Trying to gain favor with the ruling monarch.

66. Uranus
The object moved relative to the stars, but too slowly to be a comet.
Though barely visibly to the naked eye, even with a large optical telescope, it would appear a tiny, pale, slightly greenish disk.
Apparently featureless atmosphere.

67. Uranus
The axial tilt of Uranus is 98˚ …. No one knows why. Catastrophic collision? No way to find out either.
Since the north pole lies below the ecliptic plane, the planet’s rotation is considered to be retrograde.
During part of its orbit, the north pole points directly at the Sun; half a Uranian year later, the south pole points directly at the Sun.

68. Uranus

69. Uranus - Weather
Uranus is the coldest planet in the solar system, with temperatures reaching -371 F (-224 C).
Cloud layers form only at lower, warmer levels, so to see any atmospheric structure, you have to look much deeper, and the stratospheric haze makes that difficult.
Clouds and flow patterns appear to move around the planet in the sane direction as the planet’s rotation, with wind speeds of about mph ( km/hr).

70. Uranus
Storm Surge, pictures from the Keck Observatory

72. Uranus One of Uranus’ moons, Miranda.
Unusual topography believed to be caused by tidal heating, resulting from an eccentric orbit around Uranus, causing temperatures within the moon to increase and decrease, driving convection currents.
Appears to have been torn apart and reassembled

73. Neptune
Astronomers discovered quickly that there was a large discrepancy in the expected orbit - perturbation.
Although the Sun’s gravitational pull dominated, there was a small deviation causing a measureable gravitational force….there must be another planet beyond Uranus.
It took two years for John Adams to mathematically calculate the new planet’s mass and orbit; about 9 months later another mathematician independently found the same answer (Urbain Leverrier) and the two are credited with the discovery of Neptune.

74. Neptune
Neptune CANNOT be seen at all without a magnification, but is visible even with good binoculars.
Bluish dot with a few visible features…resembles a blue-tinted Jupiter
Sailing Past Neptune’s Moon Triton

75. Neptune - Weather
Neptune is farthest from the Sun, but its internal heat keeps it slightly warmer than Uranus.
Slightly thinner atmospheric haze than Uranus and less dense cloud layers
Neptune has the most violent winds in the solar system, reaching 1500 mph (2414 km/h).

77. Neptune - Weather
The Great Dark Spot just south of the equator was discovered by Voyager 2 in 1989 and was about the size of Earth.
By the time Hubble focused on Neptune to study the planet in the 90s, the Great Dark Spot was gone and a new spot, comparable
in size was visible in
the northern
hemisphere.

78. Neptune - Weather
Where these spots come from, how they age and why/how they die is not understood. They are holes in the upper atmosphere. They are likely powered by the same processes that cause the Great Red Spot on Jupiter.

79. Rings of Neptune Neptune, like the other giant planets, has rings
They are probably debris from satellites or comets that have broken up
They contain more dust than the Saturn/Uranus rings
The rings are not distributed uniformly around the ring indicating they are relatively new

80. Uranus and Neptune Coloring
Again, the primary gas for all of the jovian planets is molecular hydrogen and next up is helium.
Ammonium, which was present on both Jupiter and Saturn, is not observed in any measurable amount on either Uranus or Neptune, most likely because at the much colder temperatures, it would exist as ice crystals, not gas.
Methane is more abundant on Uranus and Neptune, accounting for their blue coloring….
Methane absorbs longer wavelengths, so the light reflected lacks red, orange and yellow.
The greater the concentration of methane, the bluer the appearance; Uranus has 2% and Neptune has 3% so which would be bluer?

81. Internal Structure – Uranus & Neptune
The internal pressures of Uranus and Neptune are low enough that hydrogen remains a gas the core.
In theory, the interior of these planets may have high-density layers of highly compressed water clouds.
It is also possible that ammonia may be dissolved in the water producing an electrically conducting layer that might explain the magnetic fields.
But, WE DON’T KNOW. 

82. Internal Structure – Uranus & Neptune
We infer theories on the cores of Uranus and Neptune based on their densities…
Low mass so the hydrogen and helium should not be as compressed, but their average densities are greater than Saturn’s – closer to Jupiter’s average density.
So, their cores must be closer to Earth-sized with about 10x the mass with compositions similar to the other two jovians.
We won’t learn much of anything more about any of the until Juno arrives to study Jupiter in

83. Internal Heating
Uranus has no internal heating source, radiating just as much heat as it receives from the Sun, having lost its initial heat to space long ago.
Neptune DOES have an internal heat source, emitting 2.7x as much heat as it receives.
This results in the convection currents which drive the cloud belts that Neptune has and Uranus does not.
WE DON’T KNOW WHY.
Perhaps the relatively high concentration of methane helps to insulate it?

84. Magnetospheres
Uranus and Neptune have magnetic fields comparable to Saturn.
Magnetospheres are populated by ions captured by solar winds or from hydrogen gas escaping from the planets below.
**The fields are not aligned with the rotation axes and are very offset from the centers – no idea why.
Uranus