Download LT debrief, Small Bodies Mars Astronomy 1 — Elementary Astronomy LA Mission College

LT debrief, Small Bodies
Mars
Astronomy 1 — Elementary Astronomy
LA Mission College
Spring F2015
Cartoon of the Day
“The universe is hilarious! Like, Venus is 900 degrees. I could tell you it melts
lead. But that's not as fun as saying, 'You can cook a pizza on the windowsill
in nine seconds.' And next time my fans eat pizza, they're thinking of Venus!”
—Neil deGrasse Tyson
“A sense of the unknown has always lured mankind and the greatest of the
unknowns of today is outer space. The terrors, the joys and the sense of
accomplishment are epitomized in the space program.”
- William Shatner
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Announcements
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Midterm not yet graded, very likely Thursday
Have you selected your observing proposal yet?
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Last Class
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Midterm
Before that Venus & Greenhouse effect LT
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
This Class
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LT Greenhouse Effect debrief
Climate Change
Small Solar System Bodies
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Meteor/oid/ite
Asteroids
Comets
Kuiper Belt
Mars (not as in depth as I’d like)
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
LECTURE-TUTORIAL
GREENHOUSE EFFECT
Which of the following is part of the Earth’s natural
greenhouse effect?
A. Earth’s atmosphere continually becomes thicker
with greenhouse gases.
B. Infrared light becomes permanently trapped in our
atmosphere by greenhouse gases.
C. The ozone hole causes significant increases in
surface temperature. D. Earth’s surface and atmospheric gases absorb
energy and then give off infrared light.
E. Heat is transferred in the atmosphere through the
circulation of greenhouse gases.
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Let’s Practice
If Earth’s atmosphere were able to completely absorb
visible light, which of the following would be true?
A. The Earth’s surface temperature would be cooler than it
is today.
B. The Earth’s surface temperature would be warmer than
it is today.
C. The Earth’s surface temperature would be the same
temperature as it is today.
D. There is not enough information to answer this question.
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
HUMANS AND CLIMATE CHANGE
Greenhouse Effect
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Is a natural process
Essential to maintain Earth’s temperature
HOWEVER
Human activity has dramatically increased the level of
greenhouse gasses
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Esp. via the internal combustion engine
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Global Warming
NASA Goddard Institute for Space Studies
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Beyond any reasonable doubt, the average
temperature on Earth is increasing.
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loss of glaciers & polar ice caps
rising sea water levels
global climate change
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Small Solar System Bodies
Astronomy 1 — Elementary Astronomy
LA Mission College
Spring F2015
METEORS
“Meteor…”
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Meteor -- The flash of light you see in the sky when a
space rock is heated to incandescence due to
atmospheric friction.
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Meteorite -- the rock, once it lands on Earth (if it is big
enough to make it intact, through the atmosphere)
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Meteoroid -- the rock, while still in space
Meteor Shower --When lots of meteors are seen in the
sky
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80 - 100 per hour is a good showing!
Caused when the Earth, on it’s trip around the Sun, passes
through a cloud of space dust/rock.
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Meteorites
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Sizes from microscopic dust to a few centimeters
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Statistically, one meteorite is expected to strike a
building somewhere on Earth every 16 months.
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Typically impact onto the atmosphere with 10 – 30 km/s
(≈ 30 times faster than a rifle bullet)
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Can come from various sources
About 2 meteorites, large enough to produce visible
impacts, strike the Earth every day.
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Meteor Showers
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Earth passing through area of debris
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Let’s Practice
Which of the following could cause a meteor shower?
A. A meteoroid hits a cloud in the atmosphere and
causes a thunderstorm.
B. The Earth crosses the debris-filled orbit of a
comet.
C. Asteroids in the same orbit as the Earth.
D. A small constellation of dying stars disintegrates.
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
ASTEROIDS
Asteroids
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Small rocky bodies that orbit the Sun.
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Millions orbit the Sun between the orbits of Mars and
Jupiter -- the asteroid belt
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Most are potato shaped (not round).
Most have craters.
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Last remains of planetesimals that built the planets 4.6
billion years ago!
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Can be stony (like Earth’s crust) or iron (like Earth’s
Core).
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The largest body in the asteroid belt (Ceres) is now
classified as a dwarf planet.
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Asteroid - Earth Collisions
http://www.hooked-nussu.org/images/stories/issue/armageddon.jpg
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Not a good thing
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Tunguska: June 30th
1908
Yucatan 65 million
years ago
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
COMETS
Comets
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Throughout history,
Comet McNaught in 2007
comets have been
considered as portents
of doom, even very
recently:
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Appearances of comet
Kohoutek (1973), Halley
(1986), and Hale-Bopp
(1997) caused great
concern among the
superstitious.
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Comets
http://thegalaxyguide.com/galaxy/
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Objects of ice/rock/dust orbiting the Sun, with
highly elliptical orbits.
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At perihelion (closest point to the Sun), a coma
and a tail typically appear due to the increased
solar radiation
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Comets: two types of tails
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Ion tail
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Ionized gas pushed
away from the comet by
the solar wind Pointing
straight away from the
sun
Dust tail
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Dust set free from
vaporizing ice in the
comet; carried away
from the comet by the
sun’s radiation
pressure. Lagging
behind the comet along
its trajectory
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Comet Nuclei
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Comet nuclei contain
ices of water, carbon
dioxide, methane,
ammonia, etc.:
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Those compounds
sublime (transition from
solid directly to gas
phase) as comets
approach the sun..
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Short Period Comets
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orbital periods of less than 200 years
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short-period comets are thought to originate from the
centaurs and the Kuiper belt/scattered disc
more-or-less in the ecliptic plane in the same direction as
the planets
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Long Period Comets
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periods ranging from 200 years to thousands or even
millions of years.
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highly eccentric orbits
orbits take them far beyond the outer planets
plane of their orbits need not lie near the ecliptic.
Believed to come from the Oort Cloud
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Let’s Practice
The orbits of long period comets are ___.
A. identical to the orbits of short period comets
B. nearly circular
C. exactly in the same plane as the planets
D. randomly oriented with respect to the orbits of the
planets
E. more than one of the above
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
The fact that short period comets have short periods
compared to long period comets implies that shortperiod comets _____ than long-period comets.
A. originate from a place closer to the Sun
B. have a different composition
C. are less massive
D. are smaller in diameter
E. have shorter tails
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
The tail of a comet is generally directed _______.
A. toward the Sun because of its gravitational
attraction
B. away from the Sun because of radiation pressure
and the solar wind
C. opposite to the direction of motion because of
interaction with interplanetary matter
D. along the comet’s magnetic field lines
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
A distant comet at its farthest point from the Sun would
have which of the following?
A. Dust tail
B. Ion tail
C. Nucleus
D. Coma
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
KUIPER BELT
The Kuiper Belt
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~ 30 – 100 AU from the
sun.
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2nd source of small, icy
bodies in the outer
solar system
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After passing Pluto, the
New Horizons
spacecraft is planned to
fly past at least one
Kuiper Belt object.
Astronomy 1 - Elementary Astronomy
NASA
LA Mission College
Levine F2015
OORT CLOUD
Origin of Comets
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Long Period comets
are believed to
originate in the Oort
cloud
Spherical cloud of
several trillion icy
bodies, ~ 10,000 –
100,000 AU from the
sun
Astronomy 1 - Elementary Astronomy
10,000 –
100,000
AU
Oort Cloud
LA Mission College
Levine F2015
Origin of Comets
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Gravitational influence
of occasional passing
stars may perturb some
orbits and draw them
towards the inner solar
system.
10,000 –
100,000
Interactions with
planets may perturb
orbits further, capturing
comets in short-period
orbits.
Astronomy 1 - Elementary Astronomy
AU
Oort Cloud
LA Mission College
Levine F2015
Let’s Practice
Short-period comets are associated with what class of
objects?
A. Kuiper Belt objects
B. Terrestrial planets
C. The Oort Cloud
D. The giant planets
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
What property of the Oort cloud is consistent with
long-period comets having orbits that are oriented
randomly with respect to the ecliptic?
A. It is very far from the Sun
B. It contains small icy bodies
C. It may interact with other stars
D. It is spherical
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Mars
Astronomy 1 — Elementary Astronomy
LA Mission College
Spring F2015
ESA’s Mars Express Flyover Video
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Key Characteristics of Mars
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~Half the size of Earth,
Hubble Space Telescope WFPC2 Image
of Mars
Cold desert world
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Once had surface water
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No magnetic field
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Two Moons
Very thin atmosphere
Unexplained
topography
Astronomy 1 - Elementary Astronomy
(Jim Bell (Cornell) et al., Hubble Heritage Team (AURA/STScI/NASA), apod010718)
LA Mission College
Levine F2015
Basic Statistics
Mars
Earth
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Equatorial Diameter =
6,782 km
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Equatorial Diameter =
12,756 km
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M = 6.4 x 1023 kg
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M = 5.98 x 1024 kg
Avrg. density = 3.9 g/cc
surf. T = -140 to +20°C
Rotation = 24h 37m
A = 1.5 AU
P = 1.9 years
e = 0.09
Astronomy 1 - Elementary Astronomy
avrg. density = 5.5 g/cc
surf. T = -50°C to +50°C
Rotation = 23h 56m
A = 1.00 AU
P = 365.256 days
e = 0.0167
LA Mission College
Levine F2015
Atmosphere of Mars
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Very thin, only 1% atmospheric pressure at surface as Earth
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Water “boils” off
95% Carbon Dioxide, few % nitrogen and argon
Little oxygen, oxygen is bound into soil (red, rust)
CO2 Gas bound in polar ice caps erupts back into atmosphere
in Spring
Mars Odessy Images of S Polar Ice Cap
NASA/JPL/MSSS
Astronomy 1 - Elementary Astronomy
Artist’s Concept
NASA; artist: Ron Miller
LA Mission College
Levine F2015
Rotation of Mars
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Martian “year”
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1.9 Earth years
Martian “day”
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24.5 hours
Axial tilt
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25° similar to Earth (23.5°)
Seasons
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Let’s Practice
Both Mars and Venus have a CO2 atmosphere. Why
isn’t Mars also very hot?
A. It is very hot!
B. It is too far from the Sun.
C. Its atmosphere is very thin.
D. The evaporation of its water cooled it.
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
MARS EXPLORATION
Past Missions to Mars -- Landers
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Pathfinder (NASA)
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1996/7 Sojourner Rover
First airbag landing, first wheeled rover on another planet
Designed as a technology demonstration
Phoenix (NASA)
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2007/8
Polar lander
Robotic arm & “bake and sniff” oven
verified the presence of water-ice in the Martian subsurface
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Current Missions to Mars
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2001 Mars Odyssey (NASA)
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2001-current (extended mission), orbiter
Studies climate, geology, minerology, abundances
Mars Express (ESA)
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ESA’s first planetary mission
2003-present (ext. mission), orbiter
subsurface radar measurements
discovered subsurface water ice
Beagle2 lander lost
Mars Science Lab (NASA)
Curiosity Rover
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Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Mars Science Lab (MSL)
Mars Rover Curiosity in Artist's Concept, Close-up (Image Credit: JPL)
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Curiosity Lander (NASA)
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You can friend the Rover on FB
Check out http://mars.jpl.nasa.gov/msl/
Launched 11/11
Landed 8/5/12
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“Seven minutes of terror”
Still going strong
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Recent Curiosity Selfie
Image Credit: NASA/JPL-Caltech/MSSS
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The scene combines dozens of images taken during
January 2015 by the Mars Hand Lens Imager (MAHLI)
camera
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Curiosity imaged on 4/22/15 by MRO
Image Credit: NASA/JPL-Caltech/Univ. of Arizona
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Where is Curiosity?
Curiosity's traverse map. (Image Credit: JPL)
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Curiosity: year of discovery
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
TOP 6 SCIENCE DISCOVERIES BY CURIOSITY
: HTTP://MARS.JPL.NASA.GOV/MSL/MISSION/
SCIENCE/RESULTS/
FROM
#1 A Suitable Home for Life:
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right chemistry to
support living microbes.
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sulfur, nitrogen, oxygen,
phosphorus and carbon
in "Sheepbed"
mudstone in
Yellowknife Bay.
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also reveals clay
minerals and not too
much salt,
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suggests fresh, possibly
drinkable water once
flowed there.
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
#2 Organic Carbon found in Mars Rocks
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first definitive detection of
organic material on Mars
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organic molecules —
carbon combined with
hydrogen/oxygen —
shows that raw
ingredients existed for life
discovered in a
powdered rock sample
from the "Sheepbed"
mudstone in "Yellowknife
Bay.”
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means that ancient
organic materials can be
preserved
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
3 Present and Active Methane in Mars'
Atmosphere:
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Last semester #4 was lack of methane!
detected a background level of atmospheric methane and
observed a ten-fold increase in methane over a two-month period.
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methane can be produced by living organisms
or by chemical reactions between rock and water,
remains a mystery at this time
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
#3 Radiation Could Pose Health Risks for
Humans
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During trip to Mars,
Curiosity experienced
radiation levels exceeding
NASA's career limit for
astronauts.
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galactic cosmic rays
(GCRs)
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particles caused by
supernova explosions and
other high-energy events
outside the solar system.
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solar energetic particles
(SEPs)
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associated with solar
flares and coronal mass
ejections from the sun.
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
#5 Thicker Atmosphere & More Water in Mars’
Past
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Mars' present
atmosphere is enriched
in the heavier forms
(isotopes) of hydrogen,
carbon, and argon.
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indicate that Mars has
lost much of its original
atmosphere and water.
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
#6 Evidence of An Ancient Streambed
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rocks are smooth and
rounded
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exposed bedrock made
of smaller fragments
cemented together,
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a sedimentary
conglomerate.
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tell a story of a steady
stream of flowing water
about knee deep
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
MRO TOP DISCOVERY
Evidence for Liquid Surface Water
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
THE SURFACE OF MARS
Surface of Mars
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Giant Volcanos
Rift Valleys
Impact Craters
Reddish deserts of broken rock
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Iron Oxide. “Rust”
Lots of visually interesting features
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Surface of Mars
False-Color Topographic Map from Mars Global Surveryor
Olympus Mons
Valles Marinaris
Hellas Basin
Argyre Basin
Northern Lowlands
Southern Highlands
Astronomy 1 - Elementary Astronomy
Impact Craters
Rift Valleys
Volcanos
LA Mission College
Levine F2015
Hemispheric Dichotomy
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The N Hemisphere is very different from the S Hemisphere
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Topography
Crust thickness
Resurfacing
? Impact, Endogenic (shifting under surface)?
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Craters on Mars
NASA/HiRISE/Univ. of Arizona)
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Vulcanism on Mars
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Shield Volcanos
Olympus Mons
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Highest & Largest in
Solar System!
Tharsis Rise
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Volcanic Bulge
10 km above mean radius
Nearly as large as the US
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Valles Marinaris
NASA JPL/
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Great Rift Valley -- Tectonic
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Could reach from LA to NY
4x deeper than Grand
Canyon
There are larger rift valleys
on Earth
Astronomy 1 - Elementary Astronomy
LA Mission College
NASA
Levine F2015
Mars Below the Surface
NASA
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Solid core - Magnetic field gone when cooled
Soft, thick mantle
No active plate tectonics
Crust ~30-150 km thick
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
What happened to the Water?
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Mars is small
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It Cooled & Lost its magnetic field
Solar wind sand blasted away the atmosphere
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Lack of atmosphere allowed Solar UV radiation to penetrate to
Mars’ surface
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UV radiation dissociated H2O molecules
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H lost to space, O reacted with Iron in the surface
rock to form iron oxide (rust)
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Mars is now Dry, and red
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Moons of Mars
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Mars has 2 Small Moons
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Tidally locked
Phobos (fear)
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prob. captured Asteroids
~22 km diameter
NASA/JPL-caltech/University of Arizona
9377 km from mars
Stickney crater and
parallel grooves
Deimos (panic)
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~12 km diameter
3x further from Mars
NASA/JPL-caltech/University of Arizona
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Let’s Practice
Mars lost its water because it lost its _____.
A. Moons
B. Magnetic field
C. Oxygen
D. Life
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Which of the necessary prerequisites for life (as we
understand it) did Mars have in the past?
A. Range of necessary chemical elements
B. Surface Water
C. Both of these
D. Neither of these
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
WRAP-UP
Topic for Next Class
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Jovian Planets & Moons
Pluto
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Reading Assignment
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Astro:5&6,
Astropedia:11&12
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Homework
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No new HW yet — very, very soon
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015