ptys 214 – spring 2011 homework #8 – due in classtoday grades are updated on d2l (please...

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

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

Extra Credit Presentation

Richard-Jacob Corona

Cristina Retamoza

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)

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)

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

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

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…

Images From Mission Animation by Dan Maas

Challenges of Planetary Exploration: Mission Phases

Launch & Cruise

Entry, Descent, Landing

Egress, Surface Operations

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

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

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

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)

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

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

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

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)

Evidence of IceIn line with NASA’s motto for Mars: “Follow the water”

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

Phoenix Instruments“Eyes”: Surface Stereo Imager (SSI)

Robotic Arm

Robotic Arm Camera Thermal and Evolved Gas Analyzer (TEGA)

Microscopy, Electrochemistry, and Conductivity Analyzer

(MECA)

Phoenix Instruments

Meteorological Station

Dust increase

Provides information about the size and location of atmospheric particles

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…

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

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)

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

Changing Weather

October 7, 2008:

The weather begins to degrade at the Phoenix landing site: storm activity increases with potential for snowfall

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

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

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

Potential Landing sites for MSL

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