life giant planets moons
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Life on Giant Planets
Stephen Eikenberry
28 October 2010
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The Jovian Planetsmuch larger than terrestrial planets
not solid - gaseous
Jupiter
Jupiter, Saturn, Uranus, Neptune
all have many moons
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Jupiter
Named after the mostpowerful Roman god
t r - r g test o ect n t e
night sky (after the Moon and
Venus)
Atmospheric bands are very
different than inner planets
called Galilean Moons
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Saturn
Named after the father of Jupiter in Greco-Roman mythology
Similar banded atmosphere Uniform butterscotch hue
any moons
Spectacularring system
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Uranus
Discovered by William
Hersc e n 1781
Named after father of Saturn
Barel visible to naked e e
Featureless atmosphere
Deviations in the expected
possibility of another planet
influencing its motion
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Neptune
There had to be anotherplanetinfluencing Uranus
1845 - John Adams determined the planets mass and orbit
10 months later - Urbain Leverrier inde endentl came u with the
same result 1846 - Johann Galle found the new planet Neptune
Bluish Jupiter atmosphere
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Space Craft Exploration of Jovian Planets
Voyager1and 2 left Earth in 1977
reached Jupiter in March and July of 1979
Used Jupiters strong gravity to send them on to Saturn -gravity assistgravity assist
oyager use aturn s grav ty to prope t to ranus an t en on to eptune
Studied planetary magnetic fields and analyzed multi-wavelength radiation Both are now headed out into interstellar space!
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Space Craft Exploration of Jovian Planets
Galileo - launched in 1989 and reached Jupiter in December 1995
Gravity assists from Venus and Earth
Two components: atmospheric probe and orbiter
Probe descended into Jupiters atmosphere
Orbiter went throu h moon s stem
Cass n m ss on to Saturn
Studying Saturns moon
Titan in much the same wa
as Galileo studied Jupiter
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Jovian Planet Properties
Most of their mass is Hydrogen and Helium light elements = low densities
High surface gravity allows their atmospheres to retain these light elements
Dense compact core at the center
But, NO SOLID SURFACE gaseous atmosphere becomes denser (eventually
liquid) at core
Differential Rotation outer regions rotate slower than inner regions
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Jovian planets - axis tilt and magnetic fields
Uranus has the most inclined rotational axis - extreme
seasons!All appear to have strong magnetic fields - rapid rotation and
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Jupiters Atmosphere
Great Red Spot
molecular hydrogen 86%
helium 14% small amounts of methane, ammonia, and water vapor
Darker colored belts lie atop downward moving
convective cells
Lighter zones are above upward moving cells
Belts are low-pressure, Zones are high pressure
As on Earth, wind moves from high to low
East/West along equator
Temperature difference between bands is main
reason for color difference
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Jupiters Atmospheretroposphere
Thin layer of white ammonia clouds
125 150 K
Colored clouds below that Warmer - 200 K
clouds are mostly droplets or
crystals of ammonium hydrosulfide At dee er levels clouds of water
ice or water vapor
The Galileoprobe survived for
about an hour before being crushed
a s a u e.
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Weather on Jupiter
Main weather feature Great Red Spot!
swirling hurricane winds
as as e over years
diameter twice that of Earth rotates with planets interior
powered by the zonal flow
Smaller storms look like white ovals (this one is over 40 years old)
Why do the storms last so long?
On Earth, hurricanes lose power when then come upon land
o cont nents on up ter not ng to stop t em once t ey start
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Saturns Atmosphere
molecular hydrogen 92.4%
helium 7.4%
traces of methane and ammonia
Layer of haze
roposp ere con a ns c ou ayers
ammonia ice
ammonium hydrosulfide ice
Overall temperature is cooler than
Ju iter
water ice
Atmosphere thickness is 3 times that
of Jupiter (caused by lower surface
Thicker clouds result in less variedvisible colors
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ea er on a urn
Computer enhanced image shows bands, oval storm systems, and
turbulent flow patterns like those seen on Jupiter
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Atmospheres of Uranus and Neptune
helium 14%
methane 2% (Uranus) 3% (Neptune)
Abundance of methane ives these lanets their blue colorMethane absorbs longer wavelength light (red) and reflects short
wavelength light (blue)
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Weather on Uranus and Neptune
UranusFew clouds in the cold upper atmosphere featureless
Upper layer of haze blocks out the lower, warmer clouds
NeptuneUpper atmosphere is slightly warmer
than Uranus (despite its further distance
from Sun)More visible features (thinner haze, less
dense clouds lie higher)
Storms Great Dark Spot
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Internal Structures models that fit the data
e a c y rogen s e qu me a
Jupiter SaturnUranus/Neptune
Increasing temperature and pressure deeper in core
Jupiter bulges at radius (7% larger)
Saturn less assymetric larger core same basic overall structureon a smaller scale
Uranus/Ne tune have a hi h densit slush below cloud level -
compressed water clouds
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Primordial Heat
-Jupiters heat source results fromstrong heating during formation by the
Generation of Heat
co apse o ma er a on o e core
-Saturn generates some eat ue to t e
gravitational contraction of helium gas
Effect of internal heating - raises the temperature of theinterior and atmosphere to higher values than expected
from the Suns heatin alone
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We see lots of life chemicals! (Water, methane, etc.)
Lightning observed too
Similar to early Earth atmosphere (?)
Ex ect com lex h drocarbons Ure -Miller ?
At some depth, have warm temps (~300K)
Methane is not a sign of life here just a sign of LOTS
of free hydrogen, some carbon, relatively little oxygen
No solid surface no oceans, no tidal pools, no claymatrix in short, no (Earth-like) places for life formation
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What about gas matrix life? (i.e. no solid surface, but life in
the air)
Wind s eed turbulence roblem tr to ut to ether a house
of cards outdoors in a hurricane
Thats easier than forming life in Jupiters atmosphere!
Convection
Causes any chemicals from warm lower layers to rise
This gives exposure to solar UV radiation, which breaksit down
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Does this mean NO life here?
Nope
Floater possibility
,
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Moons
Almost all moons inthe Solar S stem orbit
the J ovian planets J u iters 4 maor
moons are theGalilean satellites: Io,
, ,Ganymede
smaller moons
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Io
Innermost Galileansatellite
Reddish color
moo youngsurface
x reme vo cancactivity
n eror a y ea eby J upiter (& Europa)
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Io Tidal Heating
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Europa econ a ean
satellite
s , g y-
reflective color
moo sur ace wpatterns similar to ice
caps on Earth
Young surface
y uwaterworld with icecrust
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Life on Europa?
Possible view of Europan
ocean
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Life on Europa?
Europa seabed may resemble black smoker environment on
Earth (!)
Probabl little O in the water where would it come from?
But anaerobic bacteria are the basis for life in Earth vents (even iflarger life O2-dependent)
exploration mission
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Callisto & Ganymede
Rock/ice moons
v ence or some
glacial flows
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Saturns Titan
Largest moon
moot sur ace ue
to thick atmosphere (!)
n rare mages s owevidence for
continents beneath
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Titans Surface
Lakes of liquid hydrocarbon imaged from orbit via Cassini; T~85K (probably ethane/methane)
Huygens lander mission in 2006
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Titans Surface
Huygens lander mission in 2006
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Life on Titan?
Solid/liquid phase environment similar to Earths surface
Totally different chemicals and temp ranges; will not be H2O-
based like on Earth But still a possibility
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Neptunes Triton
Largest Neptunianmoon
Retrograde orbit
r a - egrees
Could indicate KBOorgn ??
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Other moons
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Enceladus
Saturn moon
ater ere too
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Enceladus
Saturn moon
ater ere too
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Summary The Giant Planets lack solid surfaces and have
extreme wind speed, turbulence and convection
Still .. we cannot rule out l ife there (floaters?) Moons such as Europa and Enceladus may have
liquid water oceans with Earth-like temperaturesand geothermal vents; these may be promising
places to search for life The moon Titan has a thick atmosphere and
(apparently) lakes/rivers of liquid hydrocarbons;tem s are COLD but we can ima ine some low-
temperature, slow-reaction life developing heretoo (?)
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