Mercury

Fun in the Sun?

First of Four Terra Planets• Stats: • Distance from Sun: 28.5 million miles• Most eccentric orbit of all planets• Will only appear in our sky just before

sunrise and just before sunset• Transits (crosses the sun) 15 times per

century. Next due May 9, 2016.• Rotates with a 3:2 ratio. (Rotates 3 times

for every 2 revolutions around the sun.

A day on Mercury

• 1 Mercurian day = 176 Earth days.

• FRY-FREEZE: 88 of these face the sun/88 away from the sun.

• Hottest is about

• 700K (800 oF) and

• coldest is

• 100 K (-280 oF.)

• 59 days for 1 rotation/

• 88 days in a period

• Radar and doppler effect

Day 59

What does the sun look like from Mercury?

Perihelion: placein orbit closestto the sun.

Aphelion: place in orbit

farthestfrom the sun.

History

• Mercury may be a fragment of a giant early collision that left only the core.

• Evidenced by the large amount of iron in the core relative to Earth.

• Core heated up/crust expanded/molten rock flowed outward/core cooled/crust contracted/and Solar tides influenced the rotation.

Mercury as observed from Earth

• Use what is known as albedo. (Amount of radiation reflected off of something.)

• Ex: mirror

• has 100%

• albedo.

Low albedo

looks dark.Know brightness of sun and

distance of Mercury from sun.

Gravity on Mercury

• Value is 3.78 m/s2

• The largest moon of Jupiter: Ganymede has a g value of only 1.42 m/s2.

• Mercury is much more dense so this

• causes the value to be higher.

Some More Details• Mercury has an atomosphere.

• It is thin and wispy. It is referred to as an exosphere.

• Made primarily of Na and O particles.

• but there is also S, He, and K at the poles.

• Mercury has a weak magnetic field. (about 1 percent of Earth’s.)

• There possible is ice at the poles.

• Mass: 3.285E23 kg, Radius 2440 km

Orbit Inclination

Messenger Mission

• http://messenger.jhuapl.edu/the_mission/MESSENGERTimeline/TimeLine_content.html

• https://www.youtube.com/watch?v=AdbVizaV9C4

MErcury Surface Space ENvironmentGEochemistry and Ranging.

Other videos

• http://messenger.jhuapl.edu/the_mission/index.html

• https://www.youtube.com/watch?v=m3ZUhpisWeQ

Review:

Gravity: 3.78 m/s2

Has many shallow craters

Has “hollows” which are

shallow small depressions

In 2015: ESA and Japan are

sending up BepiColombo which

has two orbiters: 1 to

study the magnetosphere and

the other to map the planet.

Orbit inclination is .1o