J o v i a n

1. Jovian P lanets

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. • http://www.youtube.com/watch?v=YgtuaQWdcGA • 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-https://www.youtube.com/watch?v=v9HtCAHv54E • 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 zonesalternate with darker beltsthat 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. http://nssdc.gsfc.nasa.gov/imgcat/html/object_page/vg2_p21779.html 17 http://nssdc.gsfc.nasa.gov/imgcat/html/object_page/vg1_p21258.html

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

28. The Moons of Jupiter • 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 Io Europa Ganymede Callisto

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. Ganymedeand 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 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 Io Europa Ganymede Callisto

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 http://www.astronomy.com/~/link.aspx?_id=59a77baa-117f-4cd8-b887-652df196ad50

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. http://saturn.jpl.nasa.gov/multimedia/videos/movies/PIA17652bw-small.gif

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 1056 mph (1700 km/h) • Continues lightening flashes 1000 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. http://www.universetoday.com/87269/the-sights-and-sounds-of-saturns-super-storm/

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 • http://saturn.jpl.nasa.gov/interactive/missiontimeline/ • 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.