Study Guides (248,609)
Canada (121,634)
Astronomy (142)
AS101 (137)

Lecture 21.docx

6 Pages
123 Views

Department
Astronomy
Course Code
AS101
Professor
Victor Aurora

This preview shows pages 1 and half of page 2. Sign up to view the full 6 pages of the document.
Description
Lecture 21 Recap & Preview  Mars was not able to sustain a significant greenhouse effect because its interior cooled too quickly, but evidence suggests liquid water flowed on its surface in the distant past  Jupiter is a liquid hydrogen giant with weather features driven by strong convection  Be able to describe how small bodies can undergo geologic activity  Understand how natural satellites create and maintain planetary ring systems o http://vimeo.com/40234826 another version: http://vimeo.com/24410924 Jupiter's Moons  67 natural satellites: o four Galilean moons are the largest and all orbit in Jupiter's equatorial plane o the others are smaller and mostly non-spherical → probably captured asteroids Key Observations: Io and Europa  density: 3.6 × water  rock and metal, differentiated  hundreds of volcanoes  continual resurfacing from ash → craterless http://solarsystem.nasa.gov/multimedia/display.cfm?Category=Planets&IM_ID=129  density: 3 × water  rocky w/ thin, clean icy crust  smooth areas and long ridges, few craters, “ice rafts” Why are Io and Europa Active?  few craters → moons must be geologically active  but both are too small to retain heat from formation  Step 1: resonance o Europa is exactly twice as far from Jupiter as Io; Ganymede is exactly four times as far from Jupiter as Io; o because they “sync up”, Io gets a periodic gravitational tug from the other two moons at the same spot every → Io's orbital shape is stretched into an ellipse Animation: http://commons.wikimedia.org/wiki/File:Galilean_moon_Laplace_resonance_animation.gif Why are Io and Europa Active?  Step 2: Tidal Stress  Mini-experiment: o break a piece of putty into two pieces o repeatedly stretch and expand one of the pieces o place the stressed putty on your upper lip, and then place the unstressed putty on your upper lip  What accounts for the difference? Where did the energy come from? Tides can Warm Satellite Interiors  Io's elliptical orbit, brings it closer to and further from Jupiter  recall: gravity pulls more strongly on the parts of Io that are facing Jupiter (tides); Io is repeatedly stretched when it makes its closest approach o friction warms the interior, heat flows to the cool exterior  tides also warm the interior of Europa: o cracks in surface → evidence for tidal flexing o Enough warmth for a subsurface liquid water ocean? Formation of Moons  Ganymede/Callisto: density: 1.9 and 1.8 × water → half rock, half ice  cratered / dark surface → old o dark: surface ice evaporated by “micrometeroids”  bright patches from recent craters → clean ice  observations: moons have decreasing density with increasing distance from Jupiter; all are in same orbital plane  hypothesis: moons formed in a disk of gas and dust around a warm young Jupiter, like a mini-solar system Jupiter's Rings  forward-scattering: rings are brighter when illuminated from behind o suggests composition is particles 10–7 m in size  pressure from th
More Less
Unlock Document

Only pages 1 and half of page 2 are available for preview. Some parts have been intentionally blurred.

Unlock Document
You're Reading a Preview

Unlock to view full version

Unlock Document

Log In


OR

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


OR

By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.


Submit