A1 07 Moon Mercury

Luna
LACC §8.2, 4, 5

• Know Luna’s (Earth’s Moon) interior and origin
• Know Luna’s (Earth’s Moon) surface features
and age
• Understand the Earth-Moon system
An attempt to answer the “big question”: what is
out there? Are we alone?

Thursday, March 4, 2010 1

Luna: Earth’s Moon

(red light)

http://www.lpi.usra.edu/lunar/missions/clementine/images/


Luna: Size

(red light)

http://www.astronomy.org/programs/moon/moon.html


Earth and Moon to Scale

or 239,000 ± 13,500 miles

(which amounts to 30.1 Earth diameters)
http://hyperphysics.phy-astr.gsu.edu/hbase/solar/moonscale.html#c2

It took the Apollo astronauts about three days to get
to the moon. Once they got their, they weighed only
1/6th what they did on Earth. E.g. if you weigh 100 lbs
on hear, you’d weight 17 lbs on the moon.


Earth-Moon System: Tides
The Moon is the
dominant tidal
inﬂuence because the
fractional difference in
its force across the
Earth is greater than
the fractional
difference seen from
the Sun. This difference
in force follows the
inverse square law.
http://hyperphysics.phy-astr.gsu.edu/hbase/tide.html#mstid


Earth-Moon System: Tides
http://astro.unl.edu/classaction/animations/lunarcycles/tidesim.html

http://www.atlantickayaktours.com/Pages/ExpertCenter/navigation/Navigation-4.shtml


Earth-Moon System:
Moon’s Tide Locked Orbit

When the Moon ﬁrst formed after the Giant Impact, it was much nearer to the Earth (20,000km
or 20 times nearer than present.) Both bodies exerted a pull on each other causing huge tidal
forces. ...which resulted in the slowing on both the Earth’s and the Moon’s speed of rotation. The
resultant imparting of angular momentum then caused the Moon to move further away. This
process is still ongoing, with the Earth’s days shortening by 0.0015 milliseconds per
year and the Moon moving away at about 3.8 cm a year. The Moon is no longer
slowing its rotation as it is in orbital synchronicity with the Earth. That means that it takes just as
long for it to rotate a full 360 degrees on its axis as it does to orbit once round the Earth. Will
the Moon move so far out that it may actually leave its orbit altogether? No worries; The Sun is
set to explode long before that!
http://www.math.nus.edu.sg/aslaksen/gem-projects/hm/0102-1-phase/ORIENTATIONOFTHEMOON.htm


The Moon has a
Luna: Interior
crust (C) which is
around 60 km (37
miles) thick on the (red light)

near side and even
thicker on the far
side. The mantle
(B) extends down
to a depth of 1000
km (620 miles). A
semi-molten core
(A) is probably in
the centre...
http://www.nmm.ac.uk/server?show=conWebDoc.8024&setPaginate=No


Luna: Interior

(red light)

http://www.astro.psu.edu/users/niel/astro1/slideshows/class41/slides-41.html


Our Moon’s Origin
and Evolution

http://videos.howstuffworks.com/hsw/9998-the-moon-formation-video.htm 3:32


Luna Timeline
Years Ago Event

4.5 billion A Mars sized object (about 1/10th the mass of the
Earth) impacts the Earth.

4.5 billion The accretion of material thrown into orbit by the
impact forms the Moon. Massive impacts heat the
moon resulting in differentiation, but eventually a
crust forms over magma oceans.

3.8 billion Lowland basins ﬁll with lava, forming the maria.

3.2 billion As the Moon continues to cool, volcanic activity
ceases. Meteorites impacts continue--but at an
ever decreasing rate--forming fresh craters and
lunar regolith.

(based on crater counting and radiometric dating)


Lunar Impact Rate

http://muller.lbl.gov/pages/crateringrates.htm


Current Impact Rates

http://woodahl.physics.iupui.edu/Astro100/12-25.jpg


Notable Crater:
Tycho

http://antwrp.gsfc.nasa.gov/apod/ap050305.html


Notable Crater: Tycho
Copernicus (upper left) and Tycho (lower right), each with extensive ray
systems of light colored debris blasted out by the crater-forming
impacts. In general, ray craters are relatively young as their rays overlay
the lunar terrain. In fact, at 85 kilometers wide, Tycho, with its far
reaching rays, is the youngest large crater on the nearside. Crater
Copernicus, surrounded by dark mare which contrast nicely with its
bright rays, is 93 kilometers in diameter.

http://antwrp.gsfc.nasa.gov/apod/ap050305.html


Notable Crater: Tycho
• The 170 km Baptistina parent
body disrupted ~160 My ago in
the main asteroid belt and created
many fragments.
• Many of the 1-10 km fragments
reached a nearby resonance and
escaped to the terrestrial planet
region. A few hit the Earth and
Moon.
• These fragments likely produced
the ~65 My old Chicxulub
crater on Earth and the ~110 My
old Tycho crater on the Moon.

http://www.boulder.swri.edu/science.php


Apollo Missions

http://www.lpi.usra.edu/lunar/missions/apollo/


Ice (H2O) on the Moon
Surface Temperature
Day: 107°C (225°F)
Night: 153°C (-243°F)

The Moon has no
atmosphere...this means
[ice] will rapidly sublime
directly into water
vapor and escape into
space.... Over the course
of a lunar day (~29
Earth days), all regions
of the Moon are
exposed to sunlight
[unless you’re] in a
permanently shadowed
http://www.cmf.nrl.navy.mil/clementine/
area.


You on The Moon
There is no atmosphere to speak of. You will be at the mercy of harmful
radiation and meteorites. The temperatures are extreme: 257°F days,
-283°F nights. You’ll weigh 1/6th what you do on Earth. (If you weigh
100 lbs on Earth, you’ll weigh only 17 lbs on the moon.)
A “day” will take about
29.5 Earth days. If you
can see the Earth, it will
be 1.9° on the sky (or
3 1/2 times larger than
the moon) and never
change its position in
the sky, but it will go
through phases. It took
the Apollo astronauts
about three days to get
to the moon. http://www.sciencedaily.com/releases/2007/02/070205130324.htm


Luna
LACC §8.2, 4, 5
• Know Luna’s (Earth’s Moon) interior (mantle is
solid, core is unusually small) and origin
(impact theory)
• Know Luna’s (Earth’s Moon) surface features
(highlands, maria, craters, regolith, water ice!)
and age (highlands--4.4 billion, maria--3.5
billion; young crater vs old crater)
• Understand the Earth-Moon system: tides,
tide locked orbit

LACC HW: Franknoi, Morrison, and Wolff,
Voyages Through the Universe, 3rd ed.

• Ch. 8, pp. 192-193: 14.

Due at the beginning of the next class period.
Be thinking about the Solar System Project.


Mercury
LACC §8.2, 4, 5

• Know Mercury’s interior and origins
• Know Mercury’s surface features and age
• Understand the length of a Mercury day and
year


Mercury: A Planet of Craters

This spectacular
image ... was snapped
[6 Oct 2008] ... about
90 minutes after
MESSENGER's closest
approach to Mercury,
when the spacecraft was
at a distance of about
27,000 kilometers
(about 17,000 miles)

http://science.nasa.gov/headlines/y2008/07oct_ﬁrstresults.htm


Mercury: Size
Earth Mercury Luna

Diameter: 7926 mi 3032 mi 2160 mi
2.54 1.0 0.71
http://www.arcadiastreet.com/cgvistas/mercury_002.htm
Diameter:

Mercury’s Interior

The metallic core extends from the center to a large fraction of the planetary
radius. Radar observations show that the core or outer core is molten.
Image credit: Nicolle Rager Fuller, National Science Foundation
http://www.jpl.nasa.gov/news/news.cfm?release=2007-050


Mercury Timeline
http://www.5min.com/Video/Learn-about-The-Formation-of-
Years Ago Event the-Planet-Mercury-117568413 1:19

4.5 billion Mercury forms with an unusually large iron core,
either because few lighter elements could condense
so close to the sun, or because a catastrophic
impact ripped away most of its mantle

4.5 billion
The heat of accretion results in differentiation, but
eventually Mercury cools and a crust forms. As the
planet cools, it shrinks, forming scarps. Many
craters still exist from this period within Mercury’s
intercrater plains.

3.9 billion The smooth plains form until the crust becomes too
thick for vulcanism. The rate of impacts decreases.

(based on crater counting)


Mercury: Intercrater Plains
vs Smooth Plains

Intercrater Plains w/ Old Craters Smooth Plains w/ Young Craters

Which surface is older? How can you tell?
http://photojournal.jpl.nasa.gov/targetFamily/Mercury?order=Mission&sort=ASC&start=200


Mercury: Scarps

This scarp is about 350 km (220
mi) long and transects two
craters.... The maximum height of
the scarp south of the [lower]
crater is about 3 kilometers.
Notice the shallow older crater
perched on the crest of the scarp. Ridges, Scarps, Craters

http://photojournal.jpl.nasa.gov/targetFamily/Mercury?order=Mission&sort=ASC&start=200


Mercury: Caloris Basin

The largest surface feature on Mercury is the Caloris Basin,
which resulted from a collision with an asteroid. The basin, which is more
that 1000 kilometers across, is visible as the large circular feature at the
bottom of the above photograph.
http://apod.nasa.gov/apod/ap960120.html


Mercury:
3:2 Spin-Orbit Resonance

Sidereal rotational period = 58.7 d. (sidereal day)
Period of revolution = 88 d. (sidereal year)
“a day” = 176 c. (solar day)

2:3 ratio, spin orbit coupling (58.7/88 = 2/3)
Solar day = 3 sidereal days = 2 years
http://www.csulb.edu/~gordon/LectureNotes/Mercury.html


You on Mercury
There is no atmosphere to speak
of. You will be at the mercy of
harmful radiation and meteorites.
The temperatures are the most
extreme in the solar system: 257°F
days, -283°F nights. (Lead melts at
622°F.) The sun is 1.4° on the sky
(or 3 times larger than on Earth)
and appears 6.7 times brighter. A
full “day” will take about 157 Earth
days. You’ll weigh just over a 1/3 of
what you do on Earth. (If you
weigh 100 lbs on Earth, you’ll
weigh only 38 lbs on Mercury.)

http://www.sci-ﬁ-o-rama.com/2008/08/06/
chesley-bonestell-the-surface-of-mercury/


Mercury
LACC §8.2, 4, 5
• Know Mercury’s interior (large iron core) and
origins (condensation vs impact theory)
• Know Mercury’s surface features (intercrater
planes, smooth planes, scarps, Caloris Basin)
and age (4.5 billion years)
• Understand the length of a Mercury day
(solar--157 days, sidereal--59 days) and
year (--88 days): spin-orbit resonance


LACC HW: Franknoi, Morrison, and Wolff,
Voyages Through the Universe, 3rd ed.

• Ch. 8, pp. 192-193: 18.

• Ch 9: Tutorial Quiz accessible from: http://
www.brookscole.com/cgi-brookscole/course_products_bc.pl?
ﬁd=M20b&product_isbn_issn=9780495017899&discipline_number=19

Due at the beginning of the next class period.
Be thinking about the Solar System Project.


A1 07 Moon Mercury

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