Transcript Mercury

Mercury
Vital statistics
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R = 2.440 x 106m
M = 3.30 x 1023 kg
Rorbit = 5.79 x 1010m
T = 100 - 700
Eccentricity = .206
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0.38 R
0.055 M
0.39 A.U.
Claims to fame
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Smallest planet
Highest eccentricity
Orbit displays GR effects
Only planet with
orbital/rotational resonance
other than 1:1
2nd densest planet in the Solar
System
A bit of background
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Known at least since the time
of the Sumerians (3000 BCE)
Greeks had 2 names for it
(Apollo when it appeared in the
morning, and Hermes when in
the evening), but they knew it
was the same object
• Heraclitus believed that it and
Venus orbited the Sun, not Earth
Viewing Mercury
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Since Mercury is an inner
planet, it will always look close
to the sun
Phases of Mercury
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Some views of Mercury at
different points along its orbit
(with a ground-based telescope)
Mercury’s orbit
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3:2 spin-orbit resonance
88 days to go around, 59 to
rotate
Structure
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Iron-rich core has a
radius of about 1800
km, while the radius
of the planet is only
2440 km
Mercury is probably
solid at least most
of the way to the
center (if not the
whole way)
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Magnetic field is
1/100 that of Earth,
while Venus and
Mars have no
magnetic field
Structure
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The fact that there is relatively
little mantle suggests that
Mercury underwent a very large
impact that knocked off most of
the mantle
Space visits
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3 flybys in 1974 and
1975
Can’t be observed by
HST - too close to Sun
MESSENGER was
launched in 2004, and
will orbit Mercury in
2011 after several
flybys
Mariner 10
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a) mosaic of
images taken
during
approach at
about 200,000
km above
surface
b) mosaic of
images taken
while moving
away, again
200,000 km
from Mercury
Terrain
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As Mercury’s iron core
cooled, the planet began
to shrink, compressing
the crust. This
compression produced
scarps.
This scarp is several
hundred km long and up
to 3 km high in places
Terrain
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From about 20,000 km up.
The double-ringed crater at
the upper left, named C.
Bach, is about 100km
across; it exemplifies many
of the large craters on
Mercury, which tend to have
double, rather than single,
rings. The reason is not yet
understood.
The Caloris Basin
The Caloris Basin
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Result of a HUGE impact
1400 km across
ringed by concentric mountain
ranges that reach more than
3km high in places
spans more than half of
Mercury’s radius
caused “weird terrain” at
antipodal point
Formation of the Caloris
Basin
Weird terrain on
opposite side of
Mercury
2 prominent craeters with bright halos. The craters
are about 40 km (25 mi) in diameter. The halos and
rays cover other features on the surface indicating
that they are some of the youngest on Mercury.
Discovery quadrangle