Tuesday October 9, 2012 (Our Solar System – Evolution of the Planets; Mercury & Venus; Video Segment – Journey to the Edge of the Universe)

The Launch Pad Tuesday, 10/9/12 Why are the Gas Giant (Jovian) planets more massive than the terrestrial planets, but less dense?

The Launch Pad Tuesday, 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

Announcements

Assignment Currently Open Summative or Formative? Date IssuedDate Due Date Into GradeSpeed Final Day Quiz 6S110/5 10/19 WS – Planetary Info Chart F110/510/910/11

Recent Events in Science Helix Nebula - Unraveling at the Seams mage_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 System The 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 System The 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 System  Two 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 System  Planets are composed of: Gases hydrogen and helium Rocks silicate minerals and metallic iron Ices ammonia (NH 3 ), methane (CH 4 ), carbon dioxide (CO 2 ), water (H 2 O)

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 – miles in diameter Has no atmosphere Cratered highlands Vast, smooth terrains Very dense – average 5.4 g/cm 3 (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 miles in diameter Density – 5.2 g/cm 3 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