Transcript What do you think about the origin of most of Jupiter`s moons?

Lesson 8a
Moons, Asteroids and Rings
Europa
• These interactions also keep Europa in a slight
elliptical orbit as well.
• But since Europa is farther from Jupiter the
effect is not as strong as on Io.
Europa’s interior
Possible volcanic vents on beneath
Europa
Possible Life?
New theory on Europa ice flows
• http://www.youtube.com/watch?v=7vAUMS6
VtXo&feature=related
Orbits of all of Jupiter’s moons
What do you think about the origin of most of
Jupiter’s moons?
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2.
3.
4.
Co-accretion origin
Fission origin
Capture origin
Giant impact origin
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1
25%
25%
2
3
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4
What do you think about the origin of most of
Jupiter’s moons?
Asteroid Belt
Lagrangian Points
Asteroids
Asteroids
Eros
Ida & Dactyl
Dawn mission to Vesta (current)
Phobos – Martian Moon
Deimos – Martian moon
• What is the likely origin of the moons of
Mars?
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1.
2.
3.
4.
Fission
Co-accretion
Capture
Giant impact
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3
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4
Russian probe Phobos-Grunt.
• Probe stuck in Earth’s orbit.
• Would have landed on Phobos and returned
to Earth, soil and rock samples.
• If Phobos is chemically similar to Mars, then it
could be the Phobos and Demos originated as
shot out debris from a Martian impact.
• Phobos orbits Mars every 11 hours.
• Demos orbits Mars every 30 hours.
• Mars rotates on its axis every ~ 25 hours.
• In the next 50 million years, Phobos will crash
into Mars.
Earth and the Moon
• Why will Phobos crash into Mars?
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1. Phobos is too close and Mars
33%
33%
gravity will pull it in.
2. Phobos is orbiting faster than Mars
spins. Mars is slowing it up.
3. Demos is pulling on Phobos
causing it to fall into Mars
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2
33%
3
Effect of sub-synchronous orbit.
Phobos is speeding
Up Mars rotation, and
Mars is slowing up Phobos’s
Orbital speed.
• What does this 3:1 represent?
.
1. Jupiter is 3 times farther from
Sun than
25%the 25%
25%the 25%
gap is.
2. Jupiter completes 3 orbits for every 1 gap orbit.
3. The gap is 3 times closer to the Sun than Jupiter
4. The gap completes 3 orbits for every 1 of
Jupiter’s orbits.
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2
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Keplers 3rd law relates period to
semi-major axis
• Kirkwood gap with resonance 3:1.
• Semi-major axis is a = 2.5 AU.
P2 = a3 P = (2.53)0.5 = 3.95 years
Jupiter has a = 5.2 AU.
PJ = (5.23)0.5 = 11.85 years.
11.85/3.95 = 3
This is the 3:1 resonance
Eris
Kuiper belt and scattered disk
The Planets
• Currently there is little evidence that the
planets in the Solar System are in any type of
resonance orbit.
• Example:
• Jupiter orbital period = 11.86 years
• Saturn orbital period = 29.46 years
29.46/11.86 = 2.48
Close to a 2:5 resonance
• But this wasn’t always the case.
• It has been shown with theoretical modeling
that Saturn likely formed much closer to
Jupiter.
• Also Uranus and Neptune were within 15 AU
of the Sun originally. Now they are at 19 AU
and 30 AU.
• Some models suggest that Neptune actually
formed closer to the Sun than Uranus.
• When Jupiter and Saturn formed they were
very close to 1:2 resonance orbit
The giant planets and Kuiper belt
objects.
• Jupiter and Saturn exchanged angular
momentum and finally Saturn reached a
resonance 1:2 orbit with Jupiter.
• When this happened in a very short period of
time the combined effects of the two
enormous planets was to move Uranus and
Neptune outward.
• Their motion also effect Saturn, like-wise
moved outward.
A model of planetary migration
Other models of this migration
The effect of this migration
• Jupiter moved inward in its orbit. It is thought
that this is what allowed it to capture some of
its moons and as it moved into the asteroid
belt, it picked up the Trojan asteroids in its
lagrange points.
• Neptune moved rapidly outward. Its elliptical
orbit settled down to circular by exchanging
angular momentum with the Kuiper objects.
New evidence published this year
• Gravity models using just the four gas giant
planets is not able to produce the orbits we
see today.
• Early on in the solar system it is thought that
this extra planet was sped up by interactions
and flung out of the solar system.
• Many of the Kuiper objects were moved
outward onto highly eccentric orbits. Some
inhabited a large region around the Solar
System called the Oort cloud. These are seen
today as comets when they near the Sun.
• Others were sent down to the center of the
solar system where they collided with the Sun
and the terrestrial planets.
• This time is called the “Late Heavy
Bombardment” around 4 billion years ago.
• It is thought that the large impacts that made
the Lunar Maria came from this event.
• Also Hellas crater on Mars.
• Also the axis tilts of Saturn, Uranus and
Neptune probably occurred because of this
migration.
• It is thought that the large impacts that made
the Lunar Maria came from this event.
• Also Hellas crater on Mars.
• Also the axis tilts of Saturn, Uranus and
Neptune probably occurred because of this
migration
• After the Jupiter-Saturn 1:2 resonance event,
the Solar System settled into the configuration
seen today.
New evidence published in 2011
• Gravity models using just the four gas giant
planets are not able to produce the orbits we
see today.
• By adding an additional Neptune-size planet
the orbits of the current gas-giants are
correct.
• Early on in the solar system it is thought that
this extra planet was sped up by interactions
and flung out of the solar system.