Tuesday, October 16 , 2012
Pictorial tour of the solar system and the formation of the solar system
Textbook (pg. 198 and 223)
Chapter 7 Our Planetary System
7.1 Studying the Solar System
A solar system consists of a star orbited by planets, moons, and lots of debris (comets, asteroids, dust)
- There is an inner solar system and an outer solar system
Comparative Planetology = The study of the solar system by examining and understanding the similarities and
differences among the worlds.
Planets are rocky, icy, or gassy and dont produce much energy (terrestrial planets vs. gas giants). In 2006, the
International Astronomical Union accepted a new definition of the term planet, adding one new criterion:
1. Planets orbit stars directly, not other planets.
2. Planets must be massive enough for their own gravity to compress them into spherical shapes.
3. Planets must have cleared their orbits. That means there cant be a lot of other stuff orbiting the parent star
in orbits very similar to the planet.
*This is why Pluto has been demoted to the status of dwarf planet. Other dwarf planets include Eris, Ceres,
Makemake, and Haumea.
What does the solar system look like?
The planets are tiny compared to the distances between them. Our Solar System consists of the Sun, the planets
and their moons, and vast numbers of asteroids and comets
Each world has its own unique character, but there are many clear patterns among worlds
There are two types of planets, terrestrial or Jovian
-Smaller size and mass -Larger size and mass
-Higher density -Lower density
-Made mostly of rocks and metals (especially in cores) -Made mostly of hydrogen, helium, and hydrogen
-Solid surface compounds (gas giants, incarnate not mainly gaseous)
-Few (if any) moons and faint rings -No solid surface
-Closer to the Sun (and closer together) with warmer -Rings and many moons
temperatures -Farther from the Sun (and farther apart) with colder
-e.g. Mercury, Venus, Earth, Mars, Moon thought of as a temperatures
fifth terrestrial world due to same shaping processes -e.g. Jupiter, Saturn, Uranus, Neptune
What can we learn by comparing the planets to one another?
Comparative studies reveal the similarities and differences that give clues to solar system formation and
highlight the underlying processes that give each planet its unique appearance. Insights on the processes that
have shaped other planets can help us to better understand our own and approach other planetary systems
where they may be life.
Bodies of the Characteristics
The Sun -Largest and brightest object in solar system, contains more than 98% of the systems mass so it is
more than a thousand times massive than everything else in it combined
-Gaseous, made of hot helium and hydrogen gas (about 5500C)
-Sunspots appear darker in photographs because they are cooler areas of the Sun
-Energy generated through nuclear fusion
-Shone for 5 billion years, will continue for 5 billion more2
-Most influential object in system gravity, heat influences temperatures, solar wind etc.
Mercury -No atmosphere, highly cratered surface, no active volcanoes
-Mercury has lots of small craters while the Moon only has huge splotches, also has snake-like criss-
cross lines that are absent on the Moon
-Rocky exterior with a huge iron core
-Temperatures fluctuate between -170C and 425C (lead melts at 327C) , this is because the Suns
tidal forces have caused Mercury to adopt a strange rotation pattern that gives it days and nights that
last about 3 months each
-No moons, smallest planet
-Has a magnetic field, but we dont know why
-Currently being explored by the Messenger probe (second time we have ever visited)
Venus -Thick CO2atmosphere due to very dense clouds, lots of possibly active volcanoes, rains acid
-About the same size and composition as Earth (one set of twin planets)
-Runaway greenhouse effect makes it even hotter than Mercury: 460C everywhere all the time, gentle
weather (not much deviation from extreme heat or acid rain)
-No moons, craters, or oceans
-Rotates very slowly (long days and nights, 243 days to rotate) and backwards (clockwise, west to east)
Earth -Composed of rocks and metals
-Unusually large moon relative to the size of the planet
-Only planet fit for human habitation (livable temperatures, atmosphere, water)
Mars -Very thin CO2 atmosphere so less air pressure and cold temperature
-Composed of rocks and metals, about half of Earths size
-Many huge, extinct volcanoes (e.g. Olympus Mons, largest volcano in solar system, 3x Everest)
-Was probably Earth-like in the distant past (i.e. wet & warmish)
-Many surface features appeared to be carved by water (riverbeds, floodplains, minerals, Canyon