PTYS 214 – Spring 2011 Homework #8 – DUE in classToday Grades are updated on D2L (please...
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Transcript of PTYS 214 – Spring 2011 Homework #8 – DUE in classToday Grades are updated on D2L (please...
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PTYS 214 – Spring 2011
Homework #8 – DUE in classToday
Grades are updated on D2L (please check)
Class website: http://www.lpl.arizona.edu/undergrad/classes/spring2011/Pierazzo_214/
Useful Reading: class website “Reading Material”http://en.wikipedia.org/wiki/Mars_meteorite
http://en.wikipedia.org/wiki/Exploration_of_Mars
Announcements
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HW #7
Total Students: 27
Class Average: 6.93
Low: 3
High: 10
Homework are worth 30% of the grade
Total Students: 15
Class Average: 3.2
Low: 2
High: 4
Quiz #7
Quizzes are worth 20% of the grade
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Extra Credit Presentation
Richard-Jacob Corona
Cristina Retamoza
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Mineralogical Evidence:
Martian Meteorites
Pieces of rocks ejected from Mars after impact events and reaching Earth’s surface
Of over 30,000 meteorites found on Earth, only 34 have been identified as Martian meteorites
They are also known as SNC, from the names of the most representative types (Shergotty, Nakhla, Chassigny)
Nakhla(1911)
Chassigny(1815)
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How do we know that some meteorites are from Mars?
Age separates them from other meteorites - Almost all Martian meteorites are much younger (180-1300 Myr) than most meteorites, and have a composition similar to terrestrial basalts
Oxygen isotopes separates them from Earth’s rocks - values of 16O, 17O, and 18O are distinct from terrestrial rocks and group all 34 Martian meteorites together
The isotopic composition of gases trapped in the meteorites is almost identical to the Martian atmosphere (comparison with Viking measurements)
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Comparison of Mars atmosphere measured from Viking to trapped gases in EETA79001 (Shergottite):
Values are the same!
The impact that ejected the meteorites causes some melting of the rock
The melt cooled very rapidly and formed a glass that trapped atmospheric gases
Atmospheric gases
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Evidence of Water inMartian Meteorites
Carbonate minerals - Liquid water flows through fractures in rocks and dissolved CO2 can be precipitated
Hydrated minerals have martian D/H (deuterium to hydrogen ratio)
Electron Microscope image of clay and carbonate (siderite) vein in meteorite Lafayette
ol: olivine
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Beyond Water: Evidence of life? ALH84001 is a Martian meteorite that became famous
because it appeared to contain structures that were considered to be fossilized remains of bacteria-like lifeforms
More in the next lecture…
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Images From Mission Animation by Dan Maas
Challenges of Planetary Exploration: Mission Phases
Launch & Cruise
Entry, Descent, Landing
Egress, Surface Operations
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Need powerful rockets and a lot of fuel to push the spacecraft away from Earth’s gravity
Must launch when the geometry is right for encountering the planetary object!
Challenge 1: Launch
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Navigators have to aim for a
moving target:where Mars is going to be,
not where it is at launch
Challenge 2: Traveling 250 million miles through space
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Too close to Mars and a spacecraft will go into its
atmosphere and burn up…
Too far away and it will go right by Mars and
never get captured by its gravity field!
Orbit Insertion
Challenge 3: The spacecraft needs to be precisely on target
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Entry Angle: 11º Any steeper and you get to the ground too fast!Any shallower and you skip back into space!
~ 100 20 km!
Challenge 4: Entering the atmosphere is a nail-biting time! (Landers)
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The Challenge for all Mars landers:
Take three zeros off the entry velocity in less than 6 minutes!
Challenge 5: Final Descent (Landers)
Intense heat!(need for a heat shield)
Parachute for safe landing
Navigation system to avoid surface hazards
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We never know if the mission will succeed…
The international community has sent:
~30 orbiters 16 landers 2 probes
with the goal of understanding Mars
52% of the time, Mars has won!
…but we are getting better!
20
24
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1870 1960s 1970s 1990s 2000+
Canals?
Mariner 4
Moonlikewith water?
Mariner 9 Viking
Mars GlobalSurveyor Odyssey
Fuzzy Telescope View
Giant canyons,volcanoes, wind,ancient water, &impact craters
Dynamic landscapessuggesting water and
climate cycles
No longerLunar
Subsurfacewater & minerals
Here is what we learned so far:MER
More water
HiRISEHiRISEResolves details as small as 2 feet!Resolves details as small as 2 feet!
6 m crater
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Phoenix Scout Mission
Principal Investigator is Prof. Peter Smith, University of Arizona
First mission to explore the Arctic region of Mars at
ground level
It is NASA’s first Scout Mission (missions designed to be relatively low-cost and innovative complements to NASA’s Mars Exploration Program – Phoenix total cost is $420 Million)
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Evidence of IceIn line with NASA’s motto for Mars: “Follow the water”
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HiRISE views of landing site
On Earth they develop by seasonal or episodic melting and freezing of permafrost
Region of contraction-crack polygons (from melt-freeze cycles)
Devon Island, Arctic Canada
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Phoenix Instruments“Eyes”: Surface Stereo Imager (SSI)
Robotic Arm
Robotic Arm Camera Thermal and Evolved Gas Analyzer (TEGA)
Microscopy, Electrochemistry, and Conductivity Analyzer
(MECA)
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Phoenix Instruments
Meteorological Station
Dust increase
Provides information about the size and location of atmospheric particles
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Phoenix Findings
General– confirmed the hypothesis based on orbital data
that there is shallow subsurface water ice on Mars (1-10 cm in the Martian arctic)
June 15 June 19
Ice under the spacecraft…
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Phoenix findings
Soil Properties– Very sticky– Very cloddy in some areas
Possibly cemented by carbonates and/or
other salts in presence of small amounts of water
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Phoenix Findings
Chemistry– Unexpected: perchlorate (ClO4
-) in the Martian soil (perchlorate is harmful to humans, but is used as a source of energy by some microbes)
– Carbonates: high probability of calcite, possibly other carbonates as well
implications for past climate and liquid water
– Neutral pH, around 7.7 (similar to values found by Viking)
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Phoenix findings
Weather (MET and SSI) over ~150 days
– Snow, frost formation and fog in the late summer– Water ice clouds and dust storms– Dust devils in Martian arctic
October 13, 2008: Dust devils passing 1 to 2 km from Phoenix
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Changing Weather
October 7, 2008:
The weather begins to degrade at the Phoenix landing site: storm activity increases with potential for snowfall
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Autumn Frost
Frost accumulates on the Martian
surface in the Fall
June 26, 2008 October 20, 2008
As the Sun sets over the Martian Arctic, temperatures plunge to overnight lows of -89°C (-128°F) and daytime highs in the -46° C (-50°F)
Phoenix last communication: November 2, 2008
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Next Planned Mission: MSL
(Mars Science Laboratory)
Long duration rover, much larger than Spirit and Opportunity currently on Mars
Launch: fall 2011
Goal: Assess whether Mars ever was, or is still today, an environment able to support microbial life (that is, to determine Mars’ habitability)
Challenge: - To land a very large and heavy rover on the surface of Mars
- To execute a very precise landing - To demonstrate long-range mobility on the
surface (5-10 km, or 3 to 12 mi) .
MERMSLPathfinder
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Picking a Landing Site
1. The chosen site should be the most likely place where life might have had a chance
2. Engineers must be sure the rover can safely reach the site and drive within it
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Potential Landing sites for MSL
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The Search for Life on Mars
Viking Mission, 1976: First successful landing of a spacecraft on the surface of another planet, and execution of biology experiments
Two orbiters + two landers
Cryse Basin
Elysium Mons
Hellas
Chryse Planitia
Utopia Planitia
Olympus Mons
Vallis Marineris