Mercury
Copyright (c) The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Mercury, The Innermost Planet
• Mercury is one of the least explored
planets in the Solar System
– Makes it hard to observe because it
NEVER gets more than 28º from the
Sun’s glare.
– Mariner 10 (1974) provided most of the
information we have
• flew by the planet (at 10,000 Km) and
sent pictures back to Earth.
• Mapped the whole planet
– NASA’s MESSENGER mission
returned to Mercury in 2011 for a more
in-depth study.
Mercury, The Innermost Planet
• Planet of Extremes
– On the dayside, surface temperatures is
about 800.6 degrees F (427 C)
– On the darkside, temperatures drop as
low as -297 degrees F (-183 C)
• THIS IS THE MOST
EXTREME
TEMPERATURE RANGE
between night & day OF ALL
PLANETS.
– Mostly due to NO
atmosphere
• This causes the planet to shrink and
swell.
Mercury, The Innermost Planet
• Planet “sort of”
has an
atmosphere
• BUT not really:
– thin
helium,(also
sodium,
oxygen,
potassium &
hydrogen)
Mercury, The Innermost Planet
• Atmosphere is
blown away by
the Solar Wind
of the Sun. This
is because of:
– Low gravity
of mercury.
– And…
Mercury, The Innermost Planet
• The sodium and
oxygen particles
the blistering
solar wind kicks
up are the
primary
components of
Mercury's wispy
atmosphere, or
"exosphere,“
Mercury, The Innermost Planet
• Through
interacting with
the solar wind,
they become
charged in a
mechanism that's
similar to the one
that generates the
Aurora Borealis
on Earth.
Mercury, The Innermost Planet
• Planet of Extremes
– Very eccentric orbit, coming as
close as .29 AU and as far as 0.41
AU (.387 AU)
• 1 AU = 93,000,000 miles
– (from sun to earth)
• Very elliptical orbit
• 36,000,000 miles
(35,991,000 miles)
– Tilt of 28 degrees
– Incline plane of 7 degrees
Mercury, The Innermost Planet
• Planet of Extremes
– Rotation period
– 58 days/15 min/28 sec (59 days)
– spin on axis or day & night
– Mercury rotates once every 58.647 days,
which is exactly 2/3 of its orbital period of
87.970 days, so it turns on its axis exactly 1
1/2 times during one of its years,
Mercury, The Innermost Planet
• Planet of Extremes
– Revolution period is 87.97 days (88 days)
• Rotation is one and a half times for each orbit around the sun.
• This means there are 3 days in every 2 years on Mercury
• This is the 3:2 Synchronous orbit
– Caused by:
» Close to the Sun
» Very eccentric orbit
» High Density
» Tidal Torque (pull from Sun)
– Means the same side faces SUNWARD at perihelion
• This makes it the MOST elliptical orbit of
ANY major planet
3:2 Orbital Resonance
• Mercury is tidally locked to the
Sun
– Similar to the way the Moon
is tidally locked with the
Earth
– After one orbit around the
Sun (88 days), the planet has
rotated on its axis 1.5 times
– It then takes two orbits for
Mercury to rotate three
times!
3:2 Orbital Resonance
• Mercury is tidally locked to the
Sun
– Similar to the way the Moon
is tidally locked with the
Earth
– After one orbit around the
Sun (88 days), the planet has
rotated on its axis 1.5 times
– It then takes two orbits for
Mercury to rotate three
times!
3:2 Orbital Resonance
• Mercury is tidally locked to the
Sun
– This is called a 3:2 orbital
resonance
– Sunrise and sunset are very
strange on this planet!
• The Sun actually
undergoes retrograde
motion through
Mercury’s sky!
Most likely resembles
the Moon
• Surface is covered
with craters and lava
flows
• Fewer of the craters
overlap
• Craters are similar
to the Moon’s, with
rays and crater walls
• Lower crater rims
due to Mercury’s
higher gravity
• Early in Mercury’s history, a huge
impact occurred on the surface
Caloris Basin
Caloris Basin
• Formed an
impact site
known as the
CALORIS
BASIN
Caloris Basin
CALORIS BASIN
It is a Large Basin
that almost split
planet in two.
Planet hit with
a 60 mile
wide iron
Meteor.
Leaving the
LARGEST
CRATER IN
THE S.S.
Caloris Basin
CALORIS BASIN
300Km
(812.5miles)
across and
about 1 mile
high
Caloris Basin
• The impact was so great that shock waves traveled
through the planet and shook up the terrain on the
opposite side!
Caloris Basin
• This created on the other
side (opposite) where
shock wave converged is
known as WEIRD
TERRAIN
It formed about
Kilometer or 2
per SECOND…
Also there are Cliffs
similar to earth
(Valley) called:
Scarps
Scarps
• Running across Mercury’s
surface are scarps,
kilometer-tall cliffs that are
the result of the shrinking of
the planet as it cooled
• Scarps are similar to
wrinkles in an apple’s skin
that form as it dries
• The presence of these cliffs
suggests that the core of
Mercury is large and
metallic – something that
would shrink significantly
as it cools
The Interior of Mercury
• Mercury’s density is unusually high, 5.4 kg/liter
• Indicates a very large iron core covered by a thin silicate
mantle
The Interior of Mercury
• Sounds of the Planet
https://www.youtube.com/watch?v
=894Aejo-R0U
The Interior of Mercury
• Mercury may have a
molten iron core,
despite its size
• This core may be the
cause of the weak
magnetic field (similar
in shape to the Earth’s,
but much weaker)
Why is Mercury so
dense?
• It is possible that
Mercury once had
a thicker mantle,
but a collision
removed most of
the material,
leaving only the
core and a little
lighter mantle
material behind
Unit 38
Mercury
Copyright (c) The McGraw-Hill Companies, Inc. Permission required for reproduction or display.