TuesdayOctober 9, 2012(Our Solar System –

Evolution of the Planets; Mercury & Venus; Video

Segment – Journey to the Edge of the Universe)

The Launch PadTuesday, 10/9/12

Why are the Gas Giant

(Jovian) planets more massive

than the terrestrial

planets, but less dense?

The Launch PadTuesday, 10/9/12

The Gas Giants are more massive because their strong gravitational fields drew in the light hydrogen

and helium gases that were abundant in the outer solar

system.Gas Giants are less dense because

they occupy a much greater volume than the terrestrial

planets do.Remember, Density =

mass/volume

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Summative or

Formative?Date Issued Date Due Date Into

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Quiz 6 S1 10/5 10/5 10/19WS – Planetary

Info Chart F1 10/5 10/9 10/11

Recent Events in ScienceHelix Nebula - Unraveling at the Seams

http://www.nasa.gov/multimedia/imagegallery/image_feature_2368.html

Read All About It!

A dying star is throwing a cosmic tantrum in this image from NASA's Spitzer Space Telescope. In death,

the star's dusty outer layers are unraveling into space, glowing

from the intense ultraviolet radiation being pumped out by the hot stellar core. This object, called

the Helix nebula, lies 650 light-years away, in the constellation of

Aquarius

Our Solar SystemThe planets in our solar system orbit close to a flat plane put into place by our protoplanetary

accretion disk 4.5 bya.However, the orbital planes of the planets are

slightly inclined.

Our Solar SystemThe planes of seven of the planets lie within 3

degrees of the Sun’s equator, but Mercury’s plane is inclined 7 degrees.

Dwarf planet Pluto’s plane is inclined 17 degrees.

Our Solar SystemTwo groups of planets occur in the solar system • Terrestrial (Earth-like) planets

• Mercury through Mars• Small, dense, rocky• Low escape velocities

• Jovian (Jupiter-like) planets • Jupiter through Neptune• Large, low density, gaseous• Massive• Thick atmospheres composed of hydrogen,

helium, methane, and ammonia• High escape velocities

Our Solar SystemPlanets are composed of: •Gases

hydrogen and helium•Rocks

silicate minerals and metallic iron•Ices

ammonia (NH3), methane (CH4), carbon dioxide (CO2), water (H2O)

Evolution of the Planets The Nebular Hypothesis

The planets formed about 5 billion years ago.Our solar system condensed from a gaseous nebula.As the planets formed, the materials that compose

them separated.• The dense, metallic elements (iron and nickel) sank

toward their centers.• The lighter elements (silicate minerals, oxygen, hydrogen)

migrated toward their surfaces.• This process is called chemical differentiation.

The Planets - A Brief Tour

Mercury• The innermost planet – 36

million miles from the Sun• The smallest planet – 3 015

miles in diameter• Has no atmosphere• Cratered highlands• Vast, smooth terrains• Very dense – average 5.4 g/cm3

(only Earth is denser)• Revolves quickly – only 88 days

to circle the Sun• Rotates slowly – 59 days to turn

once on its axis

Mercury

Venus• Venus is the third most brilliant

object in our sky after the Sun and Moon

• Its similar to Earth in:• Size - 7 526 miles in diameter • Density – 5.2 g/cm3

• Earth’s closest neighbor after the Moon

• Shrouded in thick clouds that are Impenetrable by visible light

• Venus’ atmosphere is 97% carbon dioxide

• The surface atmospheric pressure is 90 times that of Earth

Venus• Venus’ Surface

• Mapped by radar, not visual observation

• Surface Features• 80% of surface is subdued

plains that are mantled by volcanic flows

• Low density of impact craters• Tectonic deformation must

have been active during the recent geologic past

• Thousands of volcanic structures

Venus

Venus Radar Map of Surface

Venus

Video Segment