Download A Look at Our Solar System: The Sun, the planets and more

A Look at Our Solar System: The
Sun, the planets and more
by Firdevs Duru
Week 1
An overview of our place in the universe
An overview of our solar system
History of the astronomy
Physics of motion of the planets
Week 2
Our star Sun (physical properties, layers,
fusion)
Our home Earth (motion, interior, atmosphere,
auroras)
Our companion Moon (physical properties,
eclipses, tidal effects)
Week 3
Terrestrial planets (Mercury, Venus, Mars)
Physical properties, missions
Week 4
Jovian planets (Jupiter, Saturn, Uranus,
Neptune)
Trans-Neptunian Objects
MERCURY and VENUS
Terrestrial Planets
Huge temperature difference!
It gets very hot during the day (88 Earth days) and
very cool during the night (88 Earth days).
Two spacecraft:
Mariner 10 and
Messenger
Surface
u Crater
dominated
u Not
extensive
lava flow
regions
u Impact
meteorites
Spider
o  Not as big crater density as in the Moon.
o  Intercrater plains are seen in between.
o  Scarps: due to the cracking of the surface when the planets
core cooled and shrank.
o  Volcanic activity ended 3.8 billion years ago.
Atmosphere
Very tenuous atmosphere.
Gasses: sodium, oxygen, helium, potassium and hydrogen.
Trapped from solar wind & vaporization of the meteorites.
Uneroded old craters: not a thick atmosphere ever.
Consequence: heat cannot be retained.
Poles always cold (~125 K) –sunlight is almost parallel.
Interior
Mercury’s density: 5440 kg/m3
70% metals, 30% silicate rock
Magnetic Field
Origin of Mercury
Doppler effect can tell us about the speed and
rotation rate of the distant objects
When the source and the observer are moving with respect
to each other, a change is seen in the spectrum.
Venus rotates very slowly!
Rotation period: 243
days
1 Venus year = 1.93
Venus day
Retrograde rotation:
Rotates from east to
west.
Clouds
Extends from 45 to 75 km above the surface.
A layer of haze goes down to 30 km.
Upper-level winds: 400 km/h relative to the planet.
At the surface: 3 km/h
Entire atmosphere rotates faster than the solid planet itself.
Surface of Venus
Radargrams: radio signals sent to Venus.
Surface elevation map of Venus
VENERA 14 Spacecraft
Two features: Ishtar
Terra and Aphrodite
Terra
15 km between the
highest and lowest
points
Less than 1000
impact craters
Some volcanic
craters
Aurelia Crater
Venus shows a lot of volcanic activity
Volcanos: Maat Mons, Sif Mons and Gula Mons
Pancake-shaped lava domes
Most volcanoes are shield volcanoes: large cones and gentle
slopes.
Characteristic: Caldera or crater at the summit.
Coronae
Aine and Fotla
.
Arachnoids
Evidence for ongoing volcanic activity at Venus:
Level of sulfur dioxide above the clouds show large
fluctuations.
The orbiting spacecraft have observed bursts of radio
energy from planet’s surface.
Soviet landers found out basaltic samples implying volcanic
activity in the past.
Interior
No magnetosphere
Overall Earth-like composition
and a partially molten iron-rich
core.
Core/mantle structure similar to
ours.
No plate tectonics.
If Venus started off like Earth, why is its
atmosphere now so different from Earth’s?
On Earth:
CO2 level is controlled by its production by volcanic activities (and
human activities at some extend) and its absorption by rocks and
oceans on the surface.
Carbon cycle
At Venus, greenhouse gasses never left the atmosphere.
Why no water?
Venus, closer the Sun, it was warmer at the beginning
More water evaporation à increase of water vapor in the atmosphere
Ability of oceans and surface rocks to hold CO2 decreases with increasing
temperature à more CO2 would enter the atmosphere
Greenhouse effect would increase à Heating of the planet à increasing the
greenhouse gasses.
Finally, oceans would evaporate and all the greenhouse gasses would be in the
atmosphere.