1. The Innermost Planet
MERCURY

2. Inferior conjunction – inferior planet and Earth on same side of Sun
Superior conjunction – inferior planet and Earth on opposite sides of Sun
Conjunction

3. Mercury ☿ Smallest of the planets (Pluto etc. does not count)
Named for the swift messenger to the Roman gods

4. Little is known about Mercury
Bright in appearance but not easily seen:
Only visible at morning or evening
At most, 28.3º from the Sun
Ground based telescopes give only limited detail

5. Mercury – Physical Properties
Moon
Mercury
Earth
Radius
1700 km
1440 km
6380 km
Mass
7.3 × 1022 kg
3.3 × 1023 kg
6.0 × 1024 kg
Density
3300 kg/m3
5400 kg/m3
5500 kg/m3
Escape Speed
2.4 km/s
4.3 km/s
11.2 km/s

6. Mercury’s Orbit
Long thought to be tidally locked to the Sun; measurements in 1965 showed this to be false.
Mercury’s day and year are in a 3:2 resonance; Mercury rotates three times while going around the Sun twice.
Spin-orbit resonance – ratio of the periods can be expressed as simple integers

7. Mercury’s Orbit most eccentric orbit of all the planets
orbit is inclined by 7 degrees to the plane of the ecliptic
axial tilt is almost zero

8. Transits when Mercury comes between the Sun and the Earth
Mercury is seen as a small black dot moving across the face of the Sun
2016 May 9

9. Interior of Mercury Crust Mantle Core
Core occupies 42% of Mercury (17% for Earth)
Has higher iron content

10. Compared to Luna Mercury is much denser than the Moon
Has a magnetic field – not well understood!

11. Mercury’s Magnetosphere
Significant for size
Planetwide
Dynamo effect?
MESSENGER will measure

12. Geology of Mercury Features of Mercury’s geology: Dorsa
Impact basin’s and craters
Pit floor craters
Plains
Scarps
Volcanoes

13. Features of Mercury - Dorsa
Ridges
Caused by faults in crust

14. Features of Mercury - Craters
Mercury is very heavily cratered. More so than the Moon.
Predominant feature of Mercury
Floors can be smooth plains

15. Caloris Basin
Largest crater in solar system
1,550 Km in diameter

16. Weird Terrain
Antipodal of Caloris Basin
Where shock waves collided

17. Features of Mercury – Pit Floor Craters
Crater floor has collapsed
Possible magma chamber under crater?

18. Features of Mercury – Plains
Inter-crater plains are the oldest visible surface
occur in the regions between larger craters
Gently rolling hills
Smooth plains are widespread flat areas
resemble lunar maria
fill depressions

19. Features of Mercury - Scarps
Scarps are cliffs caused by the terrain moving vertically
On Mercury, caused by crust shrinking as planet cooled.

20. Features of Mercury - Volcanoes
evidence of lava flows
Cinder cone volcanoes
Second most important feature-former

21. Features of Mercury - Volcanoes

22. Ice? On Mercury? It’s more likely than you think.
Craters at pole may have water ice
Bottom of crater is in permanent shadow
Spotted with radar, need confirmation from MESSENGER

23. Mercury’s Atmosphere Very tenuous
about 2 trillionths of the atmospheric pressure on Earth
containing hydrogen, helium, oxygen, sodium, calcium, potassium and water vapor
Solar wind gives Mercury a tail

24. Exploring Mercury Only two missions have visited Mercury:
Mariner 10 (1973)
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry and Ranging) (2004)

25. Mariner 10 Last of the Mariner missions
Explored both Venus and Mercury
Could only map about 45% of Mercury
Same side was sunlit on each of the three flybys

26. MESSENGER Can get better pictures of Mercury
Has performed 3 flybys so far
Will enter orbit of Mercury in March 2011

27. Mercury - Summary Smallest planet
3:2 orbital resonance; most eccentric orbit
Molten iron core
Small but significant magnetic field
Impact craters are biggest feature
Ice in polar craters
Very thin atmosphere