jupiter & saturn the moons shortened version feb 15, 2011
TRANSCRIPT
Jupiter & SaturnJupiter & Saturn
The MoonsThe MoonsShortened Version Feb 15, 2011
Moons of the PlanetsMoons of the Planets
EarthEarth 1 1 MarsMars 2 2 JupiterJupiter 6363 SaturnSaturn 4747 UranusUranus 2727 NeptuneNeptune 1313 PlutoPluto 3 3
Total Total 156 (as of Nov. 8, 156 (as of Nov. 8, 2005)2005)
Galileo (1610) found the firstfour moons of Jupiter.
Jupiter’s Galilean satellites are easily Jupiter’s Galilean satellites are easily seen with Earth-based telescopesseen with Earth-based telescopes
The four Galilean satellites orbit Jupiter in the plane of its equator
All are in synchronous rotation
The orbital periods of the three innermost Galilean satellites, Io, Europa, and Ganymede, are in the ratio 1:2:4
Data from spacecraft reveal the unique properties
of the Galilean satellites
The two innermost Galilean satellites, Io and Europa, have roughly The two innermost Galilean satellites, Io and Europa, have roughly the same size and density as our Moonthe same size and density as our Moon
They are composed principally of rocky materialThey are composed principally of rocky material The two outermost Galilean satellites, Ganymede and Callisto, are The two outermost Galilean satellites, Ganymede and Callisto, are
roughly the size of Mercuryroughly the size of Mercury Lower in density than either the Moon or Mercury, they are made of Lower in density than either the Moon or Mercury, they are made of
roughly equal parts ice and rockroughly equal parts ice and rock
The Galilean satellites formed like a solar system in miniature
The Galilean satellites probably formed in a similar
fashion to our solar system but on a smaller scale
Io is covered with colorful sulfur compounds ejected from active volcanoes
IoIoHow can a smallbody like Ioremain hotenough insideto producesuch vigorousvolcanic activity ?????
Tidal HeatingTidal Heating
The energy to heat Io’s The energy to heat Io’s interior and produce the interior and produce the satellite’s volcanic activity satellite’s volcanic activity comes from tidal forces that comes from tidal forces that flex the satelliteflex the satellite
This tidal flexing is aided by This tidal flexing is aided by the 1:2:4 ratio of orbital the 1:2:4 ratio of orbital periods among the inner periods among the inner three Galilean satellites three Galilean satellites
Why Io is hot insideWhy Io is hot insideIo is pulled by the gravity of Europa and Ganymede, plusJupiter.
A resonance of 2:1 with Europa and 4:1 with Ganymedekeeps Io’s orbit slightly elliptical. (Remember whata resonance is ?)
Jupiter keeps trying to make the orbit more circular.
The gravity pull causes Io to bend and flex. This flexingproduces heat that keeps the interior molten.
What’s this for?
Io’s VolcanoesIo’s Volcanoes
At least 16 volcanoes are known, and 4-8 are At least 16 volcanoes are known, and 4-8 are erupting at any one timeerupting at any one time
Io’s volcanoes erupt about 500 cubic km of Io’s volcanoes erupt about 500 cubic km of lava each year – more than 100 times as much lava each year – more than 100 times as much as all of Earth’s volcanoesas all of Earth’s volcanoes
Eruptions on Io can shoot gas and particles up Eruptions on Io can shoot gas and particles up to 300 km (190 miles) above the surfaceto 300 km (190 miles) above the surface
Io’s VolcanoesIo’s Volcanoes
Some of the eruptions are powered by sulfur Some of the eruptions are powered by sulfur dioxide (SOdioxide (SO22) gas, which is also found in ) gas, which is also found in
Earth’s volcanoes.Earth’s volcanoes. Much of Io’s surface is covered with frozen Much of Io’s surface is covered with frozen
sulfur (yellow and black) and SOsulfur (yellow and black) and SO22 ice (white). ice (white).
Io’s volcanic eruptions produce a thin and Io’s volcanic eruptions produce a thin and variable atmosphere, mostly of SOvariable atmosphere, mostly of SO22. Auroras . Auroras
are seen in this atmosphere.are seen in this atmosphere.
Jupiter’s magnetic field makes electric currents flow through Io
The Io torus is a ring of electrically charged particles circling Jupiter at the distance of Io’s orbit
Interactions between this ring and Jupiter’s magnetic field produce strong radio emissions
Io may also have a magnetic field of its own
EuropaEuropa
EuropaEuropaEuropa has no impactcraters. It’s icy surfaceshows an intricate networkof crossing cracks, similarto cracks in the Arcticice pack on Earth.
There is very little verticalrelief (no mountains or deep valleys).
Europa’s surface is veryyoung.
Europa is covered with a smooth layer of ice that may cover a worldwide ocean
While composed primarily of rock, Europa is covered with a smooth layer of water ice
The surface has hardly any craters, indicating a geologically active history
As for Io, tidal heating is responsible for Europa’s internal heat
Minerals dissolved in this ocean may explain Europa’s induced magnetic field
Other indications are a worldwide network of long cracks and ice rafts that indicate a subsurface layer of liquid water or soft ice
Europa’s cracked and colored crustEuropa’s cracked and colored crust
Amazing structures in the Amazing structures in the icy crust of Europaicy crust of Europa
Broken and tilted icebergs floating in a frozen sea
Broken and tiltedblocks of ice
Remains ofimpactcraters ?
The flowingice has filled themin.
Europa is heated by gravitational effects of Europa is heated by gravitational effects of Ganymede and Jupiter (like Io), and therefore it has Ganymede and Jupiter (like Io), and therefore it has
an interior layer (“mantle”) of liquid water.an interior layer (“mantle”) of liquid water.
Could anything be living in the global ocean of Could anything be living in the global ocean of Europa ?Europa ?
Microbes ?More advanced creatures ?
NASA is considering a missionto Europa, to land and drillthrough the ice crust to getaccess to the liquid oceanbelow.
?
Liquid water may also lie beneath the cratered surfaces of Ganymede and Callisto
Ganymede Ganymede is highly
differentiated, and probably has a metallic core
It has a surprisingly strong magnetic field and a magnetosphere of its own
While there is at present little tidal heating of Ganymede, it may have been heated in this fashion in the past
An induced magnetic field suggests that it, too, has a layer of liquid water beneath the surface
Two types of terrain are found on the icy surface of Ganymede:
areas of dark, ancient, heavily cratered surface regions of heavily grooved, lighter-colored, younger terrain
Callisto has a heavily cratered crust of water ice The surface shows little sign of geologic activity, because there was never any
significant tidal heating of Callisto However, some unknown processes have erased the smallest craters and blanketed
the surface with a dark, dusty substance Magnetic field data seem to suggest that Callisto has a shallow subsurface ocean
Jupiter has dozens of small satellites that have different origins
As of early 2004, Jupiter has a total of 63 known satellites
In addition to the Galilean satellites, Jupiter has four small inner satellites that lie inside Io’s orbit
Like the Galilean satellites, these orbit in the plane of Jupiter’s equator
The remaining satellites are small and move in much larger orbits that are noticeably inclined to the plane of Jupiter’s equator
Many of these orbit in the direction opposite to Jupiter’s rotation
The icy surfaces of Saturn’s six moderate-sizedThe icy surfaces of Saturn’s six moderate-sizedmoons provide clues to their historiesmoons provide clues to their histories
As of early 2004, Saturn has a total of 31 known satellites
In addition to Titan, six moderate-sized moons circle Saturn in regular orbits: Mimas, Enceladus, Tethys, Dione, Rhea, and Iapetus
They are probably composed largely of ice, but their surface features and histories vary significantly
The other, smaller moons include shepherd satellites that control the shapes of Saturn’s rings and captured asteroids in large retrograde orbits
Enceladus (Moon of Saturn)Geysers of erupting liquid water announced in March 2006,
discovered by the Cassini spacecraft
This is probably the source of the “E” ring
Enceladus (Moon of Saturn)Geysers of erupting liquid water announced in March 2006,
discovered by the Cassini spacecraft
Enceladus (Moon of Saturn)Geysers of erupting liquid water announced in March 2006,
discovered by the Cassini spacecraft
Finding warm spots on the surface of Enceladus
Titan: Largest Moon in the Titan: Largest Moon in the Solar SystemSolar System
Orbital period aroundSaturn is 16 days
Thick atmosphere mademainly of N2 (nitrogen)with a small amount of CH4 (methane), which is a hydrocarbon.
Many otherhydrocarbons alsopresent.
TitanTitan Surface pressure is about 1.5 barsSurface pressure is about 1.5 bars Surface temperature -180 C (= -290 F)Surface temperature -180 C (= -290 F) Titan would be colder, but it has a Titan would be colder, but it has a greenhouse greenhouse
effecteffect that warms the atmosphere. (Which gas that warms the atmosphere. (Which gas is a is a greenhouse gasgreenhouse gas on Titan?) on Titan?)
The atmosphere is nearly opaque with organic The atmosphere is nearly opaque with organic smog, produced by sunlight acting on methane smog, produced by sunlight acting on methane and nitrogen.and nitrogen.
We can see the surface indistinctly at certain We can see the surface indistinctly at certain wavelengths where the atmosphere is partly wavelengths where the atmosphere is partly transparent.transparent.
Titan has a thick, opaque atmosphere richTitan has a thick, opaque atmosphere richin methane, nitrogen, and hydrocarbonsin methane, nitrogen, and hydrocarbons
The largest Saturnian satellite, Titan, is a terrestrial world with a dense nitrogen atmosphere
A variety of hydrocarbons are produced there by the interaction of sunlight with methane
These compounds form an aerosol layer in Titan’s atmosphere and possibly cover some of its surface with lakes of ethane
Titan is being explored by the Cassini spacecraftas it orbits Saturn.
The Huygens probe was detached from Cassiniand entered Titan’s atmosphere in January 2005.
It descended through the atmosphere, makingscientific measurements, and landed on Titan’ssurface, where it continued to make measurementsfor a few hours.
Huygens Probe Jettisoned, December 25, 2004Huygens Probe Jettisoned, December 25, 2004
Huygens’ Descent into Titan’s AtmosphereHuygens’ Descent into Titan’s Atmosphere
January 14, 2005
Titan’s Atmosphere and Surface
Organic Chemistry on TitanOrganic Chemistry on Titan
N2-atmosphere with a few % CH4
The chemistry in the atmosphere of Titan may resemble that which was at work on Earth 4 billion years ago, before the appearance of life.
Titan is a large prebiotic chemistry laboratory on a planetary scale.
But it’s very cold on Titan’s surface(-180 C), and there is no liquid water
Studying the chemistry on Titan today may be a way to sample Earth’s prebiotic chemistry 4 billion years ago.
Huygens finds flow channels on TitanHuygens finds flow channels on Titan
Hydrocarbon dust forms in Hydrocarbon dust forms in atmosphereatmosphere
Dust settles on land Dust settles on land
(H(H22O ice)O ice)
Methane (CHMethane (CH44) rains on ) rains on
Titan, washing hydrocarbon Titan, washing hydrocarbon dust into streams and lakesdust into streams and lakes
Images from the descent Probe cameras
Titan’s SurfaceTitan’s Surface
Liquid methane Liquid methane may emerge from may emerge from springs, forming springs, forming channels as it channels as it flows downhillflows downhill
Titan’s SurfaceTitan’s Surface
Islands in a stream Islands in a stream channel formed by channel formed by flowing liquid flowing liquid methanemethane
Titan landscape Titan landscape from Huygens from Huygens lander, January lander, January 14, 200514, 2005
Rounded Rounded boulders in boulders in foreground are foreground are about 4 - 15 cm about 4 - 15 cm across.across.
The boulders The boulders are probably are probably frozen Hfrozen H22O.O.
Titan SummaryTitan Summary
Titan has a thick atmosphere in which there is Titan has a thick atmosphere in which there is the active formation of complex organic the active formation of complex organic chemicals.chemicals.
These may be the chemicals that formed on the These may be the chemicals that formed on the Earth preceding the origin of life on our Earth preceding the origin of life on our planet.planet.
We study Titan to learn about the chemistry of We study Titan to learn about the chemistry of our own planet, and about other worlds where our own planet, and about other worlds where the chemistry of life exists.the chemistry of life exists.
So many moons, so little time …So many moons, so little time …