Mercury and Moon Flashcards
What are the basic information about Mercury?
- Mercury has a very elliptical orbit and is on
average 61% closer to the Sun than the Earth - Mercury is roughly 38% the size and 5% the mass of the Earth
- Mercury has virtually no axis tilt
- Even though mercury is not much bigger than
the moon is has a density close to that of the
Earth. This suggests it must have a very large iron core - Mercury’s escape velocity is roughly twice that of the Moon’s
- Mercury has a similar albedo to the Moon, reflecting 12% of the Sun’s light
Why does the same side of the Moon always face the Earth?
Synchronous Rotation
rotation period = orbital period = 27.3 days
How does Earth appear if seen from Moon?
Earth appears stationary in sky when observed from the Moon
The phase of the Earth seen from the Moon is always opposite to the phase of the Moon seen from the Earth
Where can we find Mercury on the sky?
Seen during twilight just above the horizon before sunrise or after sunset
What is the orbital and rotation period of Mercury, and their relationship?
rotation period = 59 Earth days
orbital period = 88 Earth days
3 rotations for every 2 orbits
1.5 rotations per orbit
What can you say about Mercury’s Solar Day?
Time between sunrise and sunrise: 176 Earth days
0.5 days per year
What is Mercury’s axis tilt and its consequence?
0.5, almost 0, so no season
What determines whether a planet will have an atmosphere?
Atmospheric Retention: the relative relationship between molecular motion and gravity
What is the Measure of Ability to Retain Atmosphere?
Escape velocity, ve
The stronger the gravity, the higher the escape velocity
The higher the escape velocity, the more difficult it will be for atoms and molecules
to escape
What is the Measure of Ability to Lose Atmosphere?
Mean molecular speed, vm vm ↑ T↑ Faster speeds at higher temperatures Vm ↑ molecular mass↓ Light molecules and atoms like hydrogen and helium move faster than heavier molecules and atoms like nitrogen, oxygen and argon Fast moving light gases most easily lost
What happen if vm»_space; ve?
Weak gravities and/or high temperatures Both light and heavy gases escape Result: No atmospheres! Examples: Mercury and the Moon
What happen if ve»_space; vm?
Strong gravities and/or low temperatures Both light and heavy gases retained Result: Thick atmospheres consisting of mostly hydrogen and helium (most common gases) Examples: Jovian planets
What happen if ve > vm for slow-moving heavy gases
vm > ve for fast-moving light gases?
Intermediate gravities and/or temperatures
Only heavy gases retained
Result: Thin atmospheres consisting of mostly
heavy gases like nitrogen, oxygen and carbon dioxide
Examples: Venus, Earth, Mars
What is Rilles?
Ancient lava rivers on the maria
How many missions were there to capture images of Mercury?
2
Mariner 10
Messenger Mission
