Mercury images- Similar to our Moon

Venus & Mercury

I. Mercury A. 0.4 AU from sun

1. A.U.= Astronomical unit = 93,000,000 miles This is the distance of Earth from Sun so we compare all planets to our distance.

2. close to sun in sky a) morning or evening “star” a) morning or evening “star” ( not a star but looks like one. )

b) poor photos Earth’s atmosphere distorts image Earth’s atmosphere distorts image

Earth View

B. Rotation 1. once in 59 Earth days 1. once in 59 Earth days (siderial period) Siderial means with respect to stars.

C. Revolution 1. once in 88 Earth days 1. once in 88 Earth days Time to go once around the Sun.

D. Length of day (solar rotation) (solar rotation) Earth days Earth days This is a strange effect. Look at the diagrams and I will explain it when I return.

2. One Mercury day = 2 Mercury years

3. Determine motion by RADAR Radio detection and ranging

E. Temperature 800 o F 800 o F -280 o F -280 o F

F. Albedo= 1. Light reflected 1. Light reflected Light received Light received

2. Mirror albedo is 90% Black is 0% Black is 0% Mercury is 6% Mercury is 6%

3. Dark, like moon

G. Mass % of Earth % of Earth

H. Density 1. same as Earth 1. same as Earth 2. must have iron core 2. must have iron core

I. Spacecraft Observations 1. unmanned 1. unmanned

2. Mariner 10 a) 3 flybys a) 3 flybys b) 1974 b) 1974

3. Messenger Mission Left Earth August 2004 Arrived at Mercury in 2011 Still There

4. Photographs a) craters a) craters flatter than moon flatter than moon

Why? greater gravity softer surface eroded

b) maria c) scarps cliffs hundreds of miles long cliffs hundreds of miles long

Scarps are wrinkles.... Cracks in the crust

scarp

scarp

d) Weird Terrain Grooved areas with smooth area in between Grooved areas with smooth area in between

weird terrain

Cause? 180 o from large crater

recombined shock waves from meteorite impact created Weird Terrain

5. Atmosphere a) small a) small b) sodium, helium b) sodium, helium

c) coming from craters?

6. Magnetic field a) yes a) yes

6. No moons 7. origin very different from moon

I. Mercury A. 0.4 AU from sun

Spider Crater Views from Messenger at Mercury