PTYS/ASTR 206Mars 3/22/07 Introduction to Mars. PTYS/ASTR 206Mars 3/22/07 Announcements Reading Assignment –Finish Chapter 13 Quiz today –Will cover all

PTYS/ASTR 206 Mars3/22/07

Introduction to Mars


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 10:30AM-12:00Noon – 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 10-

minute tours of the VIMS Operations Center; these tours will originate in the Atrium at 6PM – early arrival is recommended!


• 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)


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


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.




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


Synodic vs. Sidereal Periods

MARS EARTH SUN



6 months later

MARS

EARTHSUN



1 year later

EARTH

MARS

SUN



1.5 years later

EARTH

MARS

SUN



2 years later

EARTH

MARS

SUN



1 SynodicPeriodLater

EARTH

MARS

SUN



Earth-Based Views of Mars

Ground-based telescope Hubble Space Telescope


A Gallery of my attempts summer of 2003


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


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


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


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


Optical effects … againThe 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


The “Face” at higher resolution as seen with Mars Global Surveyor MOC camera


More “familiar” features


A History of Mars Exploration

• Mariner 4 (1965)– Found that Mars has

many craters



• Mariner 4 (1965)– Found that Mars has many

craters• Mariner 9 (1971)

– Found several enormous Volcanoes

– Not so dead !



• 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!)


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!)



HiRISE view of a rover next to Victoria crater


Another HiRISE image



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 ?


• 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

Valles Marineris


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


Mars’s Craters• 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


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 !


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.

Documents

PTYS/ASTR 206Mars 3/22/07 Introduction to Mars. PTYS/ASTR 206Mars 3/22/07 Announcements Reading Assignment –Finish Chapter 13 Quiz today –Will cover all