Lecture 17

Outline For Rest of Semester Oct. 29 th Chapter 9 (Earth) Nov 3 rd and 5 th Chapter 9 and Chapter 10 (Earth and Moon) Nov. 10 th and 12 th Chapter 11 (Mars, Venus, and Mercury) Nov. 17 th and 19 th Chapter 12 (Jupiter and Saturn) Nov 24 th Chapter 13 (Uranus and Neptune) Nov 26 th Thanksgiving Dec. 1 st - Exam 3 Dec. 3 rd – Chapter 14 (Pluto, and the Kuiper Belt) Dec. 8 th and 10 th – Chapter 7 and 8 (Comparative Planetology I and II) Tuesday December 15 th (7:30 am – 10:15 am) Final Exam No Reading days are scheduled this semester Exam Period begins at 7:30 a.m. on Monday, December 14 and ends on December 21

Outline For Today Discuss Quiz Finish Atmosphere Earth’s Magnetosphere The Moon –Observations –Formation Theory

Protective Shields Atmosphere Magnetic field

Key Words solar wind plasma magnetosphere northern and southern lights Van Allen Radiation belts

The Solar Wind Ions and electrons propagating toward Earth (travel time ~ 4 days) Small magnetic field in interplanetary space

The Solar Wind A plasma is created by ionizing atoms Besides sending out photons, the sun is the source of the solar wind – a plasma traveling at ~ 400 km/s When the plasma gets near Earth, the charged particles are influenced by Earth’s (internal) magnetic field. The path a particle takes is complicated – ions and electrons tend to rotate around magnetic field lines –

The Magnetosphere Charged particles moving in same direction of magnetic field are not deflected. + Magnetic field direction

The Magnetosphere Charged particles moving perpendicular to magnetic field are deflected (tend to rotate around magnetic field lines) + Region of magnetic fieldNo magnetic field

The Magnetosphere - Region of magnetic fieldNo magnetic field Electrons rotate in opposite direction around field lines.

The Magnetosphere Ions and electrons moving in opposite direction = a current … and a current creates a magnetic field … Region of magnetic fieldNo magnetic field - +

Quiz yourself otective_shield/01/minigolf.html

Far away from Earth, Solar wind distorts dipole magnetic field

Formation of the Magnetosphere

The Magnetosphere

Van Allen Radiation Belts

Ions and electrons moving bouncing along magnetic field lines Some charged particles from the solar wind are trapped in two huge, doughnut- shaped rings called the Van Allen belts

Aurora Certain solar wind conditions energize electrons and ions in magnetosphere. Some collide with atoms in Earth’s atmosphere. Collisions of charged particles atoms in atmosphere create aurora

Aurora (northern and southern lights)

Review Questions If the Earth did not have a magnetic field, do you think aurorae would be more common or less common than they are today? What is the solar wind?

From Uses color saturation

Guiding Question How did the Moon form?

Key Words capture theory co-creation theory collisional ejection theory crater far side (of the Moon) fission theory impact crater mare (plural maria) moonquake synchronous rotation terminator

The Moon’s rotation always keeps the same face toward the Earth due to synchronous rotation

How did the moon form? Observations Theory

The maria formed after the surrounding light-colored terrain, so they have not been exposed to meteoritic bombardment for as long and have fewer craters

Virtually all lunar craters were caused by space debris striking the surface There is no evidence of plate tectonic activity on the Moon Moonquakes are rare and weak

The Moon has no global magnetic field but has a small core beneath a thick mantle

Lunar rocks reveal a geologic history quite unlike that of Earth The anorthositic crust exposed in the highlands was formed between 4.0 and 4.3 billion years ago The mare basalts solidified between 3.1 and 3.8 billion years ago The Moon’s surface has undergone very little change over the past 3 billion years

Theories Fission? Capture? Co-creation? Collision (collisional ejecta theory)? How did the moon form?