Introduction to Mars
PTYS/ASTR 206
Mars
3/22/07
Announcements
• Reading Assignment
– Finish Chapter 13
• Quiz today
– Will cover all material since the last exam. This is Chapters 9-12
and the part of 13 covered today.
• Exam #2 next Thursday
– Brief review after Tuesday’s lecture
• Next study-group session is next Wednesday (3/28) from 10:30AM12:00Noon – in room 330.
• Public lecture – next Tuesday (3/27) 7:30PM in 308 of Kuiper (this
room). Prof. Bob Brown, “Saturn seen through infrared eyes”
– Look for PTYS/ASTR206 sign-up sheet (our class!)
– Note – Prof. Brown will conduct a limited number of special 10minute tours of the VIMS Operations Center; these tours will
PTYS/ASTR
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Mars– early arrival is recommended!
originate
in the Atrium at 6PM
3/22/07
• Today:
– Basic facts of Mars
– Mars’s apparitions / orbit / appearance from Earth
– Exploration
– Surface (start)
• Tuesday
– Surface (finish)
– Interior
– Atmosphere
– Water on Mars
– Moons
– Life (time permitting; otherwise, this will be discussed
later in the course)
PTYS/ASTR 206
Mars
3/22/07
Introduction to Mars
• 4th planet from the Sun
– Avg. distance: 1.524 AU
• Eccentricity: 0.093
• Year: 686.98 days
• Day: 24.62 hours
– Almost the same (differs only by
about ½ hour)
• Diameter: 6,794 km
– About ½ the size of Earth
• Mass: 6.418 x 1023 kg
– About 10 times less than Earth
• Surface temp:
– Max: 70 oF
– Min: -220 oF
– Mean: -63 oF
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Mars’ Apparitions
• Mars is best seen from Earth every
synodic period. That is every 780 days.
During this time, Mars is at opposition
and rises to its highest point in the night
sky at midnight.
– During the month or so on either
side of this, Mars is bright in the sky
and is very obvious
– also known as an “apparition”
• Because of Mars’s elliptical orbit, some
oppositions are more favorable than
others
– An especially good apparition
occurred in 2003 when Mars was at
its closest to Earth in over 50,000
years.
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Synodic vs. Sidereal Orbital Period
• Sidereal Period: The time it takes a planet to
complete a single orbit about the Sun (as seen from
the stars)
• Synodic Period: Time interval for a planet to return
to the same position relative to the Sun and Earth
(i.e. the time between successive oppositions)
• Mars has the longest synodic period of ALL the
planets
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Synodic vs. Sidereal Periods
MARS
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EARTH
SUN
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Synodic vs. Sidereal Periods
6 months
later
SUN
EARTH
MARS
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Synodic vs. Sidereal Periods
MARS
1 year
later
EARTH
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SUN
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Synodic vs. Sidereal Periods
1.5 years
later
MARS
SUN
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EARTH
Synodic vs. Sidereal Periods
2 years
later
EARTH
SUN
MARS
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Synodic vs. Sidereal Periods
1 Synodic
Period
Later
SUN
EARTH
MARS
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Earth-Based Views of Mars
Ground-based telescope
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Hubble Space Telescope
Mars
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A Gallery of my attempts
summer of 2003
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Early Observations
• Astronomers in the 1600s
made the first telescopic
observations of Mars
• They determined:
– Rotation period (24 h 37m)
– Presence of ice caps
– 25o tilt
• Linear features
– Canali (italian for channels)
– Mistranslated as canals
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Percival Lowell
• Background
– Wealthy Bostonian
– Brother was president of Harvard
– Sister won a Pulitzer prize in poetry
– Math degree from Harvard
• Decided to build an observatory in
Flagstaff
– Realized importance of seeing
conditions
– After the Mars craze, spent the rest
of his life searching for “planet X”
• Saw LOTS of canals
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Lowell’s interpretation
• Canals carry water
from Ice caps to
civilizations in the
agricultural regions
• The civilizations were
“dying of thirst”
• Evidence for intelligent
life on Mars
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Canals: Reality
• They are not there !
• Lowell almost certainly was playing
“connect the dots”
– An easy trap to get into
– Observing fine details on small
objects through a telescope is a
tough business!
– Note that they could magnify the
images considerably, but that
atmospheric turbulence limits what
can be seen at such high
magnification
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Optical effects … again
The Face on Mars
• This was seen in Viking
mission images
• Suggestive of something
built by a civilization
• Not proposed by a scientist
– Scientists never
accepted this
interpretation
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The “Face” at
higher resolution
as seen with Mars
Global Surveyor
MOC camera
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More “familiar” features
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A History of Mars Exploration
• Mariner 4 (1965)
– Found that Mars has
many craters
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A History of Mars Exploration
• Mariner 4 (1965)
– Found that Mars has many
craters
• Mariner 9 (1971)
– Found several enormous
Volcanoes
– Not so dead !
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A History of Mars Exploration
• Mariner 4 (1965)
– Found that Mars has many
craters
• Mariner 9 (1971)
– Found several enormous
volcanoes
– Not so dead !
• Viking (1976)
– Lander, Compete map of
surface (Face on mars)
– Biological experiments
(no life!)
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More Recent (and Future) Mars Missions
• Mars Pathfinder (1997)
• Mars Global Surveyor (1997)
• Both missions in 1999 failed
– Stupid mistakes
• Mars Odyssey (2001)
– Water on Mars! (UA instrument)
• Mars Express (rover Beagle failed) (2003)
• Mars Exploration Rovers: Spirit and
Opportunity (2003)
– These are still going strong (would make
for an excellent “mission update”)
• 05 – Mars Reconnaissance Orbiter
– Successful orbit insertion
– HIRISE (UA instrument) – you have GOT
to check out their website!!!
• 07
– Phoenix lander (UA mission!) Mars
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HiRISE view of a rover
next to Victoria crater
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Another HiRISE image
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Mars’s surface
• The heavily cratered southern
highlands are older and about
5 km higher in elevation than
the smooth northern lowlands
– Fewer craters in the
Northern lowlands
• The origin of Mars’s crustal
dichotomy is not completely
understood
– One giant impact basin ?
– Multiple large impact
basins ?
– Plate tectonics ?
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Valles Marineris
• A rift valley that
separates the Northern
and southern regions
– 3000-miles long
– As much as 6 miles
deep in places
• formed by upwelling
plumes of magma in
the mantle
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Mars’s Volcanoes
• Olympus Mons is an
enormous shield
volcano
– 27 km high
– 20 times wider than
it is high
• It is not active, and
neither is any other
volcano on Mars
• Mars has the largest
shield volcanoes in the
solar system
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• Mars is much more heavily
cratered than the Earth and
Venus
• Has regions with similar
crater density to that found
at Mercury and the Moon
• The largest (more than
50km wide) and smallest
(less than 5 km) craters are
similar to those found on
the Moon and Mercury
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Mars’s Craters
Splosh Craters
• Medium sized craters (~
10-20 km) have large
“ejecta blankets” which
come in a variety of
shapes
– Pancakes
– Flowers (as shown)
• May be due to
subsurface water
– Like a pebble in mud
– NOT CLEAR !
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Mars’s Interior
•
Density is 3950 kg/m3.
– This is somewhat less
than Earth's density.
– Also, Mars is smaller than
the Earth, so it could have
cooled off more inside.
– Sulfur rich?
• Magnetic field:
– Mars has no global
magnetic field.
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