Transcript Mercury

Mercury
Mercury Facts
Average distance from Sun:
0.3871 AU (57,910,000 km/35,980,000 mi)
Length of Year:
88 days
Rotation period:
58.65 days
Mean orbital velocity:
48 km/s (30 mi/s)
Inclination of axis:
2°
Average temperature:
800° F (427° C) day
-300° F (-183° C) night
Diameter:
4,878 km (3,031 mi)
Number of observed satellites:
0
Magnetic field
weak
Mercury Facts – cont.
Closest distance to Earth – 77 million km
Farthest distance from Earth – 222 million km
Mass –
3.3 X 1023 kg
Density – 5.43 g/cm3 compared to Earth’s density
of 5.51 g/cm3
EARTH
MERCURY
MOON
Mercury’s diameter is 4,880 km. That’s
40% smaller than Earth and 40% larger
than the moon
Mercury’s density is
similar to that of Earth’s at
5.42 gm/cm^3
Rocky
mantle
Mercury’s
core is
75% of its
mass, and
consists of
iron and
molten
lava
Scientists think
Scientists think Mercury’s dipolar magnetic field is
produced by its partially molten core.
Historical Facts
• Mercury is one of the five planets known to the
ancients. They called these planets "wandering stars".
• Mercury may be seen as an evening "star" near
where the sun has set, or as a morning "star" near
where the sun will rise.
• The ancient Greeks called the evening star Hermes
and the morning star Apollo, believing them to be
different objects.
• The planet is named for Mercury, the Roman
messenger of the gods.
• Named after Mercury, the
Roman god of commerce
and delivering messages
• His name comes from the
Latin word "mercari"
meaning to deal or trade.
• The planet was named
Mercury because it appeared
to move faster in the sky
than any other planet. We
now know that this was
because of its small orbit.
Mercury is not much bigger
than our Moon. It is the
smallest planet.
It is so close to the Sun that
it can be seen only in the
twilight sky of the Earth.
The hazy atmosphere near the
horizon on Earth spoils the view
of Mercury for ground-based
telescopes.
Earth-based telescopic photo of Mercury taken from
Catalina Observatory 1.5 meter (61 inch) telescope.
Mercury Orbital Facts
Until 1965, scientists thought that the same side of Mercury always
faced the Sun.
• Mercury takes only 88
Earth days to complete one
orbit
• Rotates slowly, once every
59 Earth days.
• This means that it rotates
precisely three times for
every two orbits
More Orbital Facts…
• orbits the Sun in a highly elliptical orbit at about one third of
the Sun-Earth distance.
• 46 million kilometers from the Sun at perihelion (closest),
70 million kilometers away at aphelion (furthest).
• Rotates vertically, so Mercury does not have opposite
seasons in each hemisphere like Earth does.
• “Seasonal” temperatures vary with distance from the sun.
• Extremely hot days and very cold nights. Mercury has very
little atmosphere so the surface cools down rapidly on the
night side.
Transit of Mercury
Visible from
Earth about
every 8 years.
Image of May 7, 2003 Mercury Transit was taken by NASA/ESA's SOHO (Solar & Heliospheric Observatory)
Transit of Mercury on
November 8,2006. Sunspot
#923, which is just below the
equator at the left-hand side, is
much bigger than Mercury is.
Two more sunspots at the righthand side at the equator.
Mercury appears as a small
black dot in the lower middle of
the solar disk.
Next transit: May 9, 2016
Mariner 10
• First spacecraft to use the
gravitational pull of one planet
(Venus) to reach another (Mercury).
• Instruments on board the spacecraft
were designed to measure the
atmospheric, surface, and physical
characteristics of Mercury and Venus
• Took 10,000 pictures with 57%
planet coverage
• Revealed an intensely cratered,
Moon-like surface and a faint
atmosphere of mostly helium,
resulting from solar wind
bombardment.
3 Flybys 1974-1975
Incoming View of
Mercury
This photomosaic of
Mercury was
constructed from
photos taken by
Mariner 10 six hours
before the spacecraft
flew past the planet on
March 29, 1974. These
images were taken
from a distance of
5,380,000 kilometers
(3,340,000 miles).
Close
Encounter
This two-image
mosaic of Mercury
was constructed
from photos taken
by Mariner a few
hours before the
spacecraft's
closest and first
encounter with the
planet on March
29, 1974.
Outgoing View
of Mercury
This mosaic of
Mercury was created
from more than 140
images taken by the
Mariner 10
spacecraft on March
29, 1974. The
images were
acquired after the
spacecraft exited
Mercury's shadow.
Mercury’s Atmosphere
• Mercury has almost no atmosphere and no water.
• The trace gases (oxygen, sodium, helium) that are
there are made up of atoms or ions blasted off its
surface by the solar wind.
• Mercury's extreme surface temperature enhances the
escape of these volatile atoms into space.
• No erosion from wind or water.
• Might have water ice at its north and south poles inside
craters where the sun cannot reach.
• Meteorites do not burn up due to friction because there
is no atmosphere.
Mercury’s Surface
• Highly cratered with
smooth areas.
• Relatively ancient,
volcanic surface.
• Similar to Earth’s Moon,
but fewer craters and
more “plains”.
Caloris Basin
Largest structure on
Mercury ~1300 km
Asteroid-size impactor
early in solar system
history
Basin contains smooth
plains but is highly
ridged and fractured.
Antipodal from Caloris
• "Weird terrain“,
hilly, lineated
region.
• The shock wave
produced by the
Caloris impact
caused ripples in
the crust.
Discovery Rupes
• Linear feature
• may be a thrust fault.
• Many rupes on Mercury
• Likely formed as the
rock cooled and shrunk
200 km
Mercury’s Interior
Mercury’s density is
slightly less than Earth’s,
but planet is only about
1/3 the size of Earth.
Core must be significantly
less dense than Earth’s.
Large iron core, 75% of
radius (1850 km), Silicate
mantle only 550 km thick.
Origin of Mercury’s Large Core
Unknown, but
hypotheses include:
1. Radial compositional
(iron) zonation of the
inner solar system.
2. Perhaps young
Mercury was a larger
planet, but giant impact
removed much of
mantle.
Messenger Discovery Mission
MErcury Surface, Space
ENvironment, GEochemistry,
and Ranging mission.
MESSENGER was launched
in 2004 and entered
Mercury’s orbit in 2011 to
carry out comprehensive
measurements.
It began its 2000th orbit of
Mercury on May 22, 2013.
http://www.nasa.gov/mission_pages/messenger/main/index.
html
MESSENGER’s “Science Drivers”:
First Mission
•Why are the characteristics of the core and why is it so
large compared to the mantle?
•What is the geological history of Mercury?
•What is the nature and origin of Mercury's magnetic field?
•What are the materials at Mercury's poles?
•What are the characteristics of Mercury’s gases?
Figure 2. MESSENGER mission timeline featuring major trajectory adjustments (DSM dates may change)
• At the end of MESSENGER’s initial mission, further studies
were approved.
• Now 100% of Mercury’s surface has been photographed
Science Payload
MESSENGER’s “Science Drivers”
Current Mission
• Sources of gases and how they move
• How long ago was Mercury volcanically active?
• How did Mercury's surface features change with
time?
• What is the origin of Mercury's energetic
electrons?
MESSENGER’s WAC multi-spectral
images to study compositional
variations across the surface of
Mercury. The white arrows identify
areas of Mercury’s surface that are
interpreted to be relatively young
volcanic plains, and the black arrows
point to reddish areas interpreted to be
volcanoes. Most of the color
differences studied here are believed to
indicate variations in the mineral
composition and physical state of the
rocks at different places on Mercury.
Capturing Mercury
through MESSENGER's
Dual Cameras
Date Acquired: September 29, 2009
Image Mission Elapsed Time (MET): 162709161,
162709202
Instrument: Narrow Angle Camera (NAC) and Wide Angle
Camera (WAC) of the Mercury Dual Imaging System
(MDIS)
Resolution: Top WAC image: 24.5 kilometers/pixel (15.2
miles/pixel). Bottom NAC image: 3.5 kilometers/pixel (2.2
miles/pixel).
Scale: Mercury's diameter is 4880 kilometers (3030 miles)
Spacecraft Altitude: 137,000 kilometers (85,000 miles)
Date Acquired: September 29, 2009
Image Mission Elapsed Time (MET): 162744001
Instrument: Narrow Angle Camera (NAC) of the Mercury Dual Imaging System (MDIS)
Resolution: 410 meters/pixel (0.25 miles/pixel) in the lower right corner of this image
Scale: This image is about 420 kilometers (260 miles) across
Spacecraft Altitude: 16,200 kilometers (10,100 miles)
BepiColumbo
• Named after Giuseppe
Columbo, who explained
Mercury’s rotation and
worked as a NASA advisor
for the Mariner 10 mission
• European and Japanese
Mission to Mercury
• Planned launch – 2018
• Should arrive in late 2024
• 2 Orbiters
• Original mission included a
lander, but it was cancelled
due to budget restraints