Transcript Possibilities for Life in the Solar System

A Walking Tour of the
Solar System
Lou Mayo, NASA, Goddard
How Did the Solar System Form?
-185C/370C
0.4AU
-153C
5AU
600C
-70C /50C
-161C/0C
0.7AU
1AU
1.5AU
-180C
10AU
-210C
-210C
20AU
30AU
Mercury
•Density = 5.4 cm-3 implies a metal-rich interior,
perhaps 70% iron-nickel and 30% silicate
•Because of the relatively large density of Mercury,
the core must occupy a larger fraction of the planet
than is the case for the Earth.
•Mercury is smaller than the Earth, it should have
cooled more rapidly and its solid inner core should be
an even larger fraction of the radius of the liquid core
than is the case for the Earth.
•Day and night side temperatures vary greatly!
•Tenuous oxygen, sodium, helium, and potassium
atmosphere is created by solar wind blasting particles
off the surface which quickly escape into space
Venus
Venus weak magnetic field is an
induced field from direct interaction
between the solar wind and the
ionosphere.
Equator to pole temperatures vary by
only a couple of degrees
Thick CO2 and H2SO4 atmosphere
obscures the surface in visible light
The solar wind and high atmospheric
temperatures contributed to the almost
complete loss of any water.
Size and Mass ~ Earth’s
Magellan Radar Images show evidence
for vulcanism
Earth
WATER
HEAT
ATMOSPHERE
LIFE
MAG FIELD
CIRCULAR ORBIT
Mars - Predictor of Earth’s Future?
• Mars no longer has a dynamo to generate a global
magnetic field. Strong localized magnetic fields
imbedded in the crust provide some protection for the
atmosphere against disassociation and mass loss
• But Mars probably lost most of its atmosphere and
oceans from solar wind particle collisions
Dead Volcanos
CO2, H2O Ice caps
River beds
2 Moons
Dust Storms
Thin CO2 atmosphere
Exploring Mars
Jupiter and its Moons
Lou Mayo
NASA GSFC
Io
• Orbits within intense Jovian
radiation belt
• Jovian magnetosphere strips away
about 1 ton per second of volcanic
gases and other materials.
• Causes auroras on Jupiter
• Most volcanic body in Solar
Systen
• Sulfurous plumes reach over
500 kilometers.
• Generates electric current (3M
amperes that flows along Jovian
magnetic field
Europa
• Completely covered with a frozen
ocean 100 kilometers thick.
• Few craters are visible.
• Surface ice has been resurfaced,
fractured, and rearranged in
"recent" history.
• Must occasionally be
resurfaced by tidal warming
of its global ocean.
• Conditions under ice crust
may be suitable for life.
Ganymede
•Old, dark and cratered terrain.
•Grooved with few craters terrain.
•Thick water mantle which may have
behaved like the Earth's mantle.
•Crust thickened more slowly than
Callisto's.
•Slightly larger size yields greater heat
retention.
•Ganymede was closer to Jupiter -which was very warm initially from the
heat of its formation.
•May have experienced some tidal
heating.
•Active geology persisted for the first
billion years until the crust thickened to
the point that it could no longer be
fractured through to the water mantle.
Callisto
• Callisto is heavily cratered
and shows now signs of
significant ice volcanism
or tectonism on its
surface.
• Callisto's crust formed
early and thickened
quickly.
• Callisto formed farther
from Jupiter where the
"proto-jovian" nebula
was cooler.
Cassini Saturn
March 27, 2004
30 million miles
Composite Infrared Spectrometer (CIRS)
Titan
Latest Cassini Images of Titan
•Titan’s surface is visible only in
certain infrared frequency bands and
in radar
•SS objects look different in
different wavelengths of light
Uranus
The Uranian magnetic field is tilted 60
deg. from its rotation axis
The magnetotail is twisted by the
planet's rotation into a long corkscrew
shape behind the planet.
•Tipped on its side
•11 Known Rings
•Magnetic Field
•Aurora
•H2, He, CH4, NH3
•15 moons
Neptune
Magnetic field generated by
motions of conductive material
(probably water) in its middle
layers. Tilted (47 deg)
Auroras occur over wide regions of
the planet
700mph winds detected
3 rings - composed of dark material
8 moons (7 + Triton)
H2, He, CH4, NH3
Pluto
Comets
Comet tails provided the first evidence for a solar wind
Composed of water and CO2 ice, NH3, silicates, organics
Comet Hale Bopp
Dust tail
Ion tail
Originate outside the
orbit of Pluto in Kuiper
belt and Oort cloud
Likely a prime source of
water on Earth and
perhaps amino acids
Heliosphere
(Where the solar system ends)