Download Planetary Science

Planetary Science
How we investigate the
Solar System
What we have learnt
Matter+energy=life
! 
Properties of matter
◦  Build of atoms
◦  An atom consists of
"  Protons
"  Neutrons
"  Electrons
! 
Nucleus
118 elements (H, Au, C, Ne…) defined by atomic number
◦  Atomic number, Z: number of protons
◦  Atomic mass number, A: number of protons+neutrons
! 
Isotopes are versions of the same element but with different number of
neutrons
Isotope
12C
13C
14C
# protons
# neutrons
6
6
6
6
7
8
most abundant
stable isotope
least abundant, is
radioactive/
unstable
Chemical properties of isotopes identical, although 12C reacts faster.
Molecules
! 
A molecule is two or more atoms combined
◦  E.g. H2, CH4, NH3
! 
A compound is a substance with molecules made
of at least two elements
◦  E.g., H2O
! 
Organic molecules/compounds are
molecules containing carbon
◦  E.g., C6H12O6
Phases of matter
! 
Substances can exist in three phases
◦  Solid, liquid or gaseous
◦  Properties depend on the phase due to the strength of the chemical
bond
"  Hotter temp (gas), less strong bond
"  Cooler temp (liquid, then solid), stronger bonds
"  Temperature is a measure of the motion of the particles: high temperatures,
lots of motion!
! 
Melting point is the temperature at which water molecules break
the solid bonds of ice => liquid phase
! 
Boiling point is the temperature at which water molecules break the
bonds of liquid water => gaseous phase
! 
Sublimation is when molecules escape from a solid
◦  E.g. freeze-drying
! 
Evaporation is when molecules escape from a liquid
◦  E.g., drying paint
Energy forms
! 
Energy is “the ability to do work”
◦  Kinetic energy – energy due to motion (falling rock)
◦  Potential energy – stored energy, due to gravitational field (rock on a
ledge, planet on distance from central star)
◦  Radiative energy – energy carried by electromagnetic waves (light)
! 
Energy can change matter
◦  Makes us walk, break molecules apart
Light
! 
Light is electromagnetic radiation, defined by its
◦  wavelength (distance between crests, m),
◦  frequency (time interval between crests, Hz or m-1)
! 
In interactions with matter best described as photons, which are packages
of energy
While being carried in space, best described as a wave
! 
! 
A picture is worth 1000 words, but a spectrum is worth 1000
pictures
! 
Taking spectra is one way we can find out information about
objects
◦  Continuous spectrum
◦  Emission line spectrum
◦  Absorption line spectrum
! 
Lines in a spectra occurs at very specific frequencies
determined by the atoms/molecules in a gas
◦  If we can see the lines, we know what material is in the region we’re
observing!
! 
How we measure temperatures of objects
◦  Take measurements at a few different wavelengths, then fit a black
body (thermal radiation) curve to it.
Planetary science
! 
Observations of the Solar system finds:
◦  Inner planets close in space
◦  All planets orbiting the Sun in the same direction, and more or less in
the same plane
◦  Sun rotates in the same direction as the planets orbit
! 
These observations have to be explained by a theory of how
the solar system was formed.
! 
It also has to explain the distinction of Terrestrial versus
Jovian planets.
Terrestrial and Jovian planets
! 
! 
Four inner planets: Mercury,Venus, Earth, Mars (Terrestrial)
Outer planets: Jupiter, Saturn, Uranus, Neptune (Jovian)
Other Solar system objects
! 
Asteroids
◦  Mainly made of metal and rock
◦  Asteroid belt between Mars and Jupiter
! 
Comets
◦  Mainly made of rock and ice
◦  From the Kuiper belt and the Oort cloud
! 
Dwarf planets – Kuiper belt objects
◦  Larger objects (like comets) in the Kuiper belt
◦  Example Pluto, Eris
Moons
! 
Important Solar system objects
◦  Ganymede, Io, Callisto, Europa…
How were all these objects formed?
! 
Solar nebula and the nebular theory
◦  Theory of origin of our solar system
! 
Starts our from a big molecular cloud (nebula)
◦  A collapse starts due to unstable conditions (outside pressure not
equal to inside pressure any longer)
! 
The law of conservation of energy
◦  Energy cannot be created or destroyed
◦  It can be transformed to a different form
"  Gravitational potential energy => heat
! 
The law of conservation of angular momentum
◦  Measure of the spin of an object, L=mrv
◦  Has to be conserved: if radius smaller, the velocity increases