Mercury Flashcards
What is the orbital period of Mercury
88 days
When did MESSENGER enter orbit
Mar 2011
What two things are interesting about Mercury’s core
What might this mean
It 85% of Mercury’s radius (65% volume, c.f. 17% for earth)
It has an outer liquid core
It might mean that alot of Mercury’s content was blasted off by a major impact early in the planet’s life (there are other theories)
It also means Mercury has a dynamo based magnetic field - like earth, and unlike Mars or Venus
What is the rotational period of Mercury
What’s the catch
58.6 days (sidereal days - in the frame of reference of fixed background stars)
Relative to the sun it is 176 days (very nearly two times the length of its year - so on Mercury a day lasts two Mercury years)
What is the diameter of Mercury (km)
4,879km
What two spacecraft have visited Mercury
What three things make missions to Mercury difficult
Mariner 10 (launched 1973) - flyby
MESSENGER (launched 2004) - orbit
You have to go fast to catch up with it (but slow down fast to orbit it, just when the Sun’s trying to make you go faster)
The pull of the Sun makes orbits unstable
The temperature of the Sun makes maintaining a stable spacecraft temperature difficult
Who observed the first transit of Mercury through a telescope
What did it allow him to do
Pierre Gassendi in 1631
He made the first reliable measurement of Mercury’s diameter
What is the temperature range on Mercury
430C during the day to
-180C at night
What is Mercury’s axial tilt
0.01 degrees - very small
What does MESSENGER stand for
Mercury surface, space environment, geochemistry and ranging)
What did the Greeks call Mercury originally
At first they thought it was two planets, the one they saw in the morning they called Apollo, and the one at night they called Hermes
In the end when they figured it was one planet they called it Hermes
How many AU is Mercury from the Sun
and in km?
What is the catch?
- 387
58m km
It has the highest orbital eccentricity of any planet so at aphelion it is 1.5 x further out than at perihelion
What is Mercury’s Spin Orbital Resonance
3:2
3 spins to every 2 orbits
Essentially this means spin and orbits are synchronised every two years –> you can work out the solar day
How much has Mercury’s diameter shrunk in the last 4 billion years
What features give this away
up to 10km
lobate scarps (aka cliffs)
What is the Latin name for cliffs
What are the cliffs on Mercury named after
Rupes
So the scarps on Mercury are called Rupes
Vessels of discovery (e.g. Endeavour)
