Science
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Oct28_planetary_science.pptxPlanets of the solar system- a closer look
Three types:
Rocky (like Earth)
Smaller, close to sun
Terrestrial planets
Mercury
Venus
Earth
Mars
2. Big and gassy like Jupiter
Jovian planets
(Jove is synonym for Jupiter)
Jupiter
Saturn
Uranus
Neptune
And a third type is the dwarf planets which are small, cold, icy and similar to many satellites: Example: Pluto and the Galilean satellites of Jupiter
Goal today
Lay out differences emphasis on earth’s uniqueness
Main causes of variations size and distance from sun
(a minor cause of variations may be presence of a large moon
… more complicated, we’ll discuss over several lectures)
Main types of variations temperature of planet,
its atmosphere (or lack)
surface features/geology
presence of water or ice
We’ve already discussed this
Venus is too close to the sun too hot, oceans boiled away
Mars is too far too cold, water and dry ice no liquid
Earth is just right for liquid water the “Goldilocks Zone”
Size considerations
Bigger planets have more gravity can capture and keep a
thicker atmosphere. Its why the Jovian planets are gas giants.
Today, we focus on the smaller ones terrestrial and dwarf planets/icy moons
(and Earth’s moon)
Mercury
Moon
Start with some pictures- differences emerge
Earth
Mars
Venus
Whats the difference?
Earth photo
Mars photo
Google Earth
Google Mars
Clouds in the photo
Photo is hazier
Mercury
Moon
Atmospheres: Earth, Venus, and Mars have them
Mercury and Moon do not too small (gravity too weak)
Earth
Mars
Venus
Venus: Our Evil Twin
Almost exactly the same size as Earth,
but choked in poisonous clouds of
sulfuric acid. Hellish conditions.
Atmosphere much thicker than earth-
acts as blanket (extreme greenhouse
effect- future lecture topic)
Surface temp = that of a self cleaning
Oven
The Russians landed a spacecraft on its
surface and it got fried after a couple of
minutes! We don’t know too much about
Its geology; there are probably volcanoes
Astronauts will never visit.
Note: Venus once might have been more habitable, but being
too close to the sun- the oceans evaporated away
Right now, Mars is more similar to Earth
even though its only 1/2 the diameter
Because Mars is significantly smaller, it has weaker gravity and
can’t keep as thick an atmosphere as the earth.
But still, some photos from the surface look strangly
familiar……….
What does this look like?
And This
Mars has sedimentary rock and sand like Earth. How did it get sand?
Weathering and erosion can occur on Mars (but very slowly since its air
pressure is so low (air is thin)).
Which is which planet? (Mars or Earth?)
PSC 121 Prince George's Community College
Did Mars have liquid water?
What are these?
Whats the similarity?
Whats the difference?
Yes! Mars has evidence for dried up rivers
and sedimentary rock
14
An old stream and delta
Fun facts: rotation of Mars is 25 hours (almost identical to Earth)
seasons/weather are somewhat similar (except no rain)
Mars has water, probably all frozen
Frost on Martian surface
Impact Craters: Whats the difference?
Mars Moon
Mars fewer than the moon. They aren’t as “sharp”- more eroded
Cratering: an important tool to study surfaces of planets and satellites
Surface of Callisto
Surface of Europa
Mars
Mercury
Craters do exist on Earth (rare)
Manicougan crater- Canada
(view from earth orbit)
Meteor Crater, Arizona, ¾ miles across
Crater Lake, OR: from a volcano
Ring-lake is 45 miles across
The meteor was 3 miles wide
215 million years ago (early Mesozoic)
The meteor was 160 feet across, 50,000 years ago
Panoramic view of Meteor Crater
What’s happening to this crater?
Its being weathered and eroded away in a few 100 thousand
years, it will be gone
Cratering and surface changes
Misconception: Earths atmosphere protects us.
No! (ask the dinosaurs)
Reality: How fast craters disappear tells you about
weathering/erosion
Longer term: plate tectonics/volcanoes completely
change the surface
All planets get craters. They all get hit by meteors
Surface age
No weathering/erosion.
Altho there were some
Lava flows at one point
The grey basalt
Some weathering
And erosion
Earth’s surface is
Very young
Zoomed in shot of horizon. Including haze in the atmosphere
Three possibilities for lack of craters on Pluto
one hypothesis- in the outer solar system, things move
more slowly. They don’t crash with the same impact.
2nd hypothesis. Ice can slowly flow (like glaciers)-erodes
the craters
3rd hypothesis. Pluto does have a thin atmosphere. Some weathering?
The ices of Pluto: how many of the magnificent 7 elements do we have? What’s missing?
Fe (iron) and silicon- those are for rocks (Pluto is an ice world)
And Helium- mostly on the sun or Jupiter/Saturn
Carbon monoxide
On earth (and Venus and
Mars, we also have
CO2: carbon dioxide
Landforms of the Solar System
Both planets have mountains/volcanos
Olympus Mons on Mars. Largest
volcano in the solar system (25 km)
Mt. Everest: Highest mountain
on Earth (9 km)
Surface of Mars: Elevation changes
Rift Valley?
volcanos
Martian mountains come in bunches, not ridges like the earth. Why?
What you don’t see on Mars (or anywhere else in the solar system)
Plates!
Rock Formation: Earth, Moon and Mars
Why is igneous rock present on all three objects?
Why is metamorphic rock not likely to exist in great
amounts on Mars? (if at all)
| Earth | Mars | Moon | |
| Igneous | Y | Y | Y |
| Sedimentary | Y | Y | N |
| Metamorphic | Y | N | N |
If Mars doesn’t have metamorphic rock, and doesn’t have
Plate tectonics, what other rock should it not have
(hint: it’s a type of igneous rock)
Granite on Mars? (maybe)
The specific chemical varieties include things not found on Mars before. But apart from rounding out Mars’ rock collection, they have some pretty interesting things to tell us about Mars’ early history. The granite-like rocks are similar to some of the rocks that make up Earth’s earliest truly continental crust, which differs from the basalt that makes up the seafloor. That could have come about by partly melting pre-existing basalts that began to sink back into Mars’ still-soft interior, for example.
Regardless of how it happened, the idea that there was continental crust being manufactured on Mars makes that planet’s early history look more like the Earth’s than we thought. The researchers also note that the existence of some of these rocks “challenge[s] the simple idea of continuous cooling of the Martian mantle over geologic time, pointing to more complex global or local variation in mantle temperature”.
Curiosity finds continent-building rocks on Mars
Early Mars may have been a bit more like early Earth.
SCOTT K. JOHNSON - 7/13/2015, 6:35 PM
What makes Earth unique:
1. Only planet currently in the Habitable zone
present day surface liquid water
2. Only planet with plate tectonics. Earth’s surface
gets recycled more than any other planet
Consequence for types of rocks found
3. Largest moon compared with the planet (to be
discussed next week)
Obviously: abundant life (but that’s biology,
and this is not a biology class! So the
three characteristics above are what really
counts in this class)
One unknown: do other planets have a liquid in their cores and
a mantle like the earth? Not sure. Recent evidence for
Mercury says it might have liquid in its core
Little Differences
Craters on earth are rare because weathering and erosion is more rapid
Moon has no atmosphere most craters (actually Mercury because no lava flows)
Mars has a thin atmosphere a lot of craters, more weathered and eroded than the moon
Summary of Earth Compared to other solar system objects
Similarities
Cratering and volcanism on Earth, moon and Mars
Sediments on both Earth and Mars (moon is all igneous rock)
River features on both Earth and Mars
Some atmospheric weathering (sand), ice,
and evidence of past liquid water on Mars but not the moon
Some other moons around other planets are totally covered in ice
Big Differences
Earth is the only object in the solar system with plate tectonics
probably only object with lots of metamorphic rocks
probably only object with long mountain ridges (and folds/faults)
probably the only object with significant amounts of granite
Earth is the only object in the solar system with liquid surface water
