Interiors of Terrestrial Planets
Mercury
•MEAN RADIUS: 2439.7 km
•MASS: 0.055 (Earth=1)
•DENSITY: 5.43 (g/cm^3)
•GRAVITY: 0.376 (Earth=1)
•ORBIT PERIOD: 87.97 (Earth days)
•ROTATION PERIOD: 58.65 (Earth days)
•SEMIMAJOR AXIS OF ORBIT: 0.387 au
•ECCENTRICITY OF ORBIT: 0.206
The Resonant Rotation of Mercury
Mercury’s large core may
indicate a “mantle-stripping”
impact with a similar body.
1 solar day =
176 Earth days
1 sidereal day=
59 Earth days
Venus
•MEAN RADIUS: 6051.9 km
•MASS: 0.814 (Earth=1)
•DENSITY: 5.24 (g/cm^3)
•GRAVITY: 0.903 (Earth=1)
•ORBIT PERIOD: 224.7 (Earth days)
•ROTATION PERIOD: 243.0 R (Earth days)
•SEMIMAJOR AXIS OF ORBIT: 0.723 au
•ECCENTRICITY OF ORBIT: 0.007
The External Appearance of Venus
Venus in visible light – cloud shrouded
Venus in the ultraviolet – cloud
patterns rotate every 4 days.
Radar Maps of Venus
The Magellan probe provided a high resolution elevation map of
Venus, with information on reflectivities that indicate textures.
Craters on Venus
Volcanoes on Venus
The Real Surface of Venus
Actual pictures from the ground -- the Soviet Venera series
Temperature: 800 degrees, Pressure: 100 atmospheres
Mars
•MEAN RADIUS: 3388.0 km
•MASS: 0.108 (Earth=1)
•DENSITY: 3.94 (g/cm^3)
•GRAVITY: 0.380 (Earth=1)
•ORBIT PERIOD: 686.98 (Earth days)
•ROTATION PERIOD: 1.026 (Earth days)
•SEMIMAJOR AXIS OF ORBIT: 1.524 au
•ECCENTRICITY OF ORBIT: 0.093
Clouds, Polar Caps, and Odd Markings
Mars presents many different aspects
to us. Its weather and terrain are
varied and changeable.
Valles Marineris Canyon
The Volcanoes of Mars
Martian Terrains
Polar Ice fields
Old cratered
highlands
Dune Fields
Evidence of Water Flows
Water cannot be a liquid on Mars’
surface now, but billions of years
ago it flowed (there may even
have been seas.
The Surface Desert of Mars
Mars looks like a desert with about the
same land area as the Earth. Its pink
skies, however, contain far too little
pressure to allow outside living.
The Martian Meteorite
This rock IS from Mars.
Does it contains signs of life?
Stay tuned….
Martian Moons: Phobos and Deimos
Mars’ moons are very small;
almost certainly captured
asteroids. Phobos orbits in
less than a day – retrograde.
The Atmospheres of the Terrestrial Planets
The Greenhouse Effect
1) In equilibrium, a planet
must re-radiate all the
energy it absorbs.
2) Solar energy tends to be
converted from visible to
infrared radiation.
3) Some gases are
transparent to visible
radiation, but opaque to
infrared radiation.
4) When radiation is
blocked, you need a
bigger temperature
gradient to push the
energy through.
Evolution of Terrestrial Atmospheres
All the terrestrial planets start off with a
substantial atmosphere. Mars lost most of it
because of low escape speed. Earth
converted most of the carbon dioxide into
rocks. Life produced free oxygen. Venus lost
the water because it stayed vapor (and solar
UV released hydrogen).
Summary of the
Terrestrial
Planets
These are the “rocky”
worlds of our inner
solar system. The
other large solid
bodies in the solar
system are all moons
of the outer gas giant
planets. They were
collected by impacts
of smaller bodies,
and still bear those
scars and effects.