Test #2 Study Notes These are the study notes for the second test on the planets. In this note there is detailed information on every planet as well as their important moons. This got me a great mark on the test!

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Life beyond Earth Study Notes
Environmental Requirements for Habitability
- It must have a source of molecules from which to build living cells
- It must have a source of energy to fuel metabolism
- It must have a liquid medium for transporting the molecules of life
There are two main planet types for the planets in our solar system
Terrestrial Planet – Mercury, Venus, Earth and Mars -------- inner solar system
Gas Giants – Jupiter, Saturn, Uranus and Neptune -----------outer solar system
***Planets listed in order from the sun***
Tidal Heating: Tidal heating is the heating of the interior
of one planetary body caused by stresses induced from the
gravitational pull of another.
- Mercury’s surface looks much like that of the moons, there are many craters that
cover the entire surface.
- Mercury is much smaller than earth and because of this has lost internal heat
- There is no longer any volcanism on mercury
- Mercury is essentially airless because no volcanic activity means no outgassing
into the atmosphere
- One of the least likely to be habitable
- No liquids anywhere on the surface because of the high surface temperatures
- 58.6 day rotation period and an 87.9 day orbital period
- day temperature 425 celcius
- Almost certainly lifeless
- Large iron core does generate a magnetic field 1% the strength of earths \
- Nearly identical to earth in size…. Named “sister planet”
- Completely shrouded by thick clouds
- Mariner 2 discovered that the surface is scorching hot about 470 celcius
- A thick atmosphere bears down on the surface about 90 times the strength of
- These extreme conditions are caused by an overwhelmingly strong greenhouse
- Carbon dioxide makes up 96% of the atmosphere where its 1% on Earth
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- At altituded about 50km above the surface where the greenhouse gas effect is
much weaker, liquid water droplets can and do exist in the clouds
- Volcanism or tectonics have shaped the reshaped or paved over rocks from earlier
- The red colour of the surface is a result of high levels of iron oxide (rust) in the
surface material
- Mars is tilted on its axis at 25 degrees, very similar to earths 23.5degress and also
clearly goes through seasonal changes. The tilt however is not as constant as
earths, but changes with time. This can lead to drastic climate change
- Mars has polar caps at the north and south poles. These clearly melt in the
“summer” and refreeze in the “winter” on mars
- These polar caps that are changing is actually the freezing of not water but carbon
- First mission to mars was in july of 1965 when mariner 4 flew by and transmitted
22 pictures of the Martian surface.
- The crust of mars is clearly divided into distinct hemispheres. The southern region
tends to be at a higher elevation and is much more craters than the northern
- This implies that the north is younger rock which has been resurfaced by some
mechanism since the bombardment of the surface.
- Northern hemisphere has clear evidence of past volcanic activity
- The two main regions of volcanoes on mars are the elysium and tharsis bulge
- Tharsis bulge contains 4 very large volcanoes, in particular Olympus Mons (3
times the size of Everest)
- Only shield volcanoes on mars
- Mars however despite the presence of volcanoes does not show any evidence for a
system of plate tectonics to have developed as on earth
- The height of the shield volcanoes like Olympus mons is due to the fact that the
hot spot under the surface that produced these features never moved.
- Although mars has either a small iron core ort a larger iron sulphur core, it has
only an extremely weak magnetic field, with mostly localized features. There
does seem to be evidence in the rock that in the past mars’ field may have been
much stronger. This also includes some features that look somewhat like the sea
floor magnetic stripping we see here on earth.
- Like Venus, mars has an atmosphere that is mostly carbon dioxide, however mars
is a smaller world with only about 40% of the gravitational surface strength of
earth. So its atmosphere is only about 1% as thick as Earth’s. This atmosphere
does contain traces of oxygen and water vapour. There is enough water vapour to
produce a thin cloud cover on the surface
- Also there is enough air on mars for the planet to have weather. Since mars axis is
tilted similar to earths it does experience seasons
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- Mars also has two very small moons, Phobos the closer at only 6000km from the
surface and Deimos the smaller which is much further out. (Talk about later)
- The recent rovers that are currently operating on mars – spirit and opportunity
have found evidence in rock of mineral deposits and other water deposition
features that most accept as conclusive proof that water once flowed on the
surface of the planet.
- Today it is though most of the water is frozen as permafrost metres below the
surface, and may extend 100’s of metres down.
- pure ice glaciers covered by rock are common at mid latitude levels.
- Debris covered glaciers at mid latitudes on mars may contain enough ice to cover
the entire planet in 20 cm of water
- mars missions suggest that mars once had a thick c02 atmosphere and liquid water
- Most methane in earth’s atmosphere is produced by life, raising questions about
the origins of mars.
- Methane gas was recently detected in mars’ atmosphere using ground based
- Most methane in earth’s atmosphere is produced by life, raising questions about
the origins of mars.
- Atmosphere of mars – CO2 – 95.32%, nitrogen – 2.7%, Argon – 1.6%, Oxygen
0.13%, Carbon – 0.08%
- The past flow of liquid water demonstrates the potential for habitability
Gas Giants – Jupiter and Saturn
Both these planets are made up of a large amount of H and He (hydrogen and helium)
- They are something like 90% H, 10% He, and traces of other elements. For this
reason these objects have a much lower average density than the inner rocky
planets. Saturn’s average density is actually less than liquid water.
- The interiors of these two objects have a similar structure.
- The next layer is of molecular hydrogen, this is a thin layer in Jupiter and a much
thicker layer in Saturn
- The part we refer to as the atmosphere of these planets is only a very thin layer of
around 300km in depth
- In this outer later we refer to as the atmosphere, we see a number of chemicals
that would be useful to life such as ammonia, water, and methane. The intense
conditions on these planets make it seem unlikely life could evolve there, but
the materials are present that life could use
- There is a rich carbon chemistry that happens in the atmosphere of Jupiter (and
probably Saturn as well, the current casssini probe will tell us more.
- These atmospheres have intense weather. The coloured bands on Jupiter and
Saturn represent convection currents. The lighter areas are zones where hotter
gasses are rising while the darker are gasses falling
- We all see enormous circular storms. On Jupiter the most famous is the great red
spot – a giant storm that has been circulating since we have taken observations of
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