Transcript Goal to get to know the moons of Saturn a bit better and

Goal to get to know the moons of
Saturn a bit better and to
understand the atmosphere and
surface of Titan
Objectives:
1) To explore some of the moons of
Saturn and their important features
2) To learn about Atmosphere of Titan
3) To explore the Surface of Titan
courtesy of the Huygens probe.
Janus and Epimetheus
• These two moons (181 km and 116 km in
size) share an orbit – sort of.
• They swap positions every 4 years. Janus is
the innermost right now, but will swap again
in 2010.
• While their orbital distance differ by only 50
km, they never get closer than 15000 km to
each other.
Pandora/Prometheus – F ring
Some newer inner moons
http://saturn.jpl.nasa.gov/multimedia/videos/videodetails.cfm?videoID=158
Run for your lives, it’s the Death Star!
• Phew, it is
just Mimas.
• Very ice, very
old surface.
• The Herschel
crater is 140
km in
diameter.
• Mimas is 400
km in
diameter.
Enceladus
•
•
•
•
Somehow the south pole
has warmed and partially
melted.
Geysers have been
created as a result, and
the surface of Enceladus
is being covered over by
fresh snow.
Enceladus has the most
reflective surface in the
solar system (reflects
90%), and would make
the best place in the
solar system to ski.
Diameter = 500 km, and
somehow the rotation of
the moon is slowing (and
it is flattening).
To scale
Enceladus – 40% closer to Saturn than our moon is to us
Ice volcanoes!
Why Enceladus, and not Mimas?
• You need a full tug of war, and Enceladus
has a 2:1 orbital resonance with Dione.
• So, it gets just enough tidal heating for
geologic activity at the south pole.
• Some ramifications… This means that
Enceladus has some atmosphere!
Enceladus atmosphere!
• The atmosphere is mostly water vapor and
if pretty thin.
• Like on Io, the atmosphere is localized,
and not global.
• Being small, it cannot hold onto it, so it has
to be replenish it (with the eruptions).
• This loss of water vapor is the source for
the E ring!
3 miles wide!
Explore, hike, and/or ski the mountains
and craters of Enceldus’s older side
Results
The E ring
• 1000 km in
diameter.
• Very icy, and
very old.
• Lots of craters.
• Density close to
water.
• Oddly, this moon
has two small
“trojan” moons
which share its
orbit (60
degrees in front
and in back) –
Calypso and
Telesto
Tethys
More batterings
• 4 large craters
The companions to Tethys
• Telesto - 24 km
• Young, +60 degrees
Calypso - 22 km
60 degrees behind
Dione
• 560km in
diameter.
• About
same
distance
from
Saturn as
our moon
is from
earth.
• Mostly old
surface,
but has
strange
cracks.
Tale of two sides
High res
Dione’s companions
• Helene (32 km)
leading
• Polydeuces
• 3 km discovered
2004
Rhea
Skipping Titan for now, Hyperion
• 266 km in
size.
• Largest
irregular
shaped
moon in the
solar system.
• Different
color
possibly from
falling
objects.
• Very sponge
like and low
density
Wierdest moon! Hyperion
• Very low density
• Means lots of
holes
• When it gets hit
ejecta escapes
instead of falling
into other
craters.
• 280 km across
• In addition, the
crater floors get
a dark material
that allows it to
heat up and
vaporize ices
http://saturn.jpl.nasa.gov/multimedia/videos/video-details.cfm?videoID=109
Iapetus
• Very
bizarre
surface.
• Due to
newly
discovered
ring
created
from
Phoebe
Iapetus
• By Saturn
shine.
• The star
trails are
due to
orbiting
and a 82
second
exposure.
• craters and 6
mile mountains
http://saturn.jpl.nasa.gov/multimedia/videos/videodetails.cfm?videoID=105
Phoebe
• Very battered. The outermost of the sizable
moons of Saturn (200 km in diameter)
Titan!
•
•
•
•
1 of 2 moons with an atmosphere.
Atmosphere is 40% higher pressure than Earths!
Mostly Nitrogen
The orange is
a methane haze.
• HST image.
• To see the
surface requires
a probe!
Titan’s atmospheric profile
Huygens probe
• http://saturn.jpl.nasa.gov/multimedia/video
s/video-details.cfm?videoID=117
• http://saturn.jpl.nasa.gov/multimedia/video
s/video-details.cfm?videoID=124
Further Fly Bys
• http://saturn.jpl.nasa.gov/multimedia/video
s/movies/PIA09183.mov
Clouds – N. Pole
Jet
stream!
Rivers
?
Xanadu
The “rocks” of
Titan
• But not stone,
frozen water.
• But at these
temperatures,
water is hard as
rock.
• Surroundings is a
watery, tarry
version of sand.
Volcano
?
RAIN!
• In the mornings (which last 3 earth days
out of its 16 earth day rotational period)
you get a morning drizzle!
• The drizzle is of course METHANE!
• Where does this methane in the
atmosphere come from though?
• Evaporation from lakes or from
volcanoes?
• Only future probes will be able to find out.
Conclusion
• Most of Saturn’s moons have old,
cratered, icy surfaces.
• Some moons are quite strange.
• Enceladus is creating a new ring!
• Titan has evidence for methane rivers and
lakes and once maybe a methane ocean
and needs to be studied a lot more.