ptys/astr 206life / exo planets 5/1/07 extraterrestrial life and … extrasolar planets

PTYS/ASTR 206 Life / Exo Planets5/1/07

Extraterrestrial life and … extrasolar planets


Announcements

• Final exam – Thursday, May 10 11AM-1PM– Brief review today

• Pick up past assignments!

• Office Hours– Jade: not in this week– John: as usual– Me: as usual– Email for times other than office hours


Have we Been Visited by Aliens ?

Check out: http://www.ufoevidence.org/photographs/photohome.asp


A UFO panel convened to discuss all of the current evidence:

The Sturrock Panel

• They concluded that the UFO problem is not a simple one– No simple, universal answer– Whenever there are

unexplained observations, there is the possibility that scientists will learn something new by studying those observations.

– Example: “ball lightning”


Visual Evidence example: UFOs and Ball Lightning

• UFOs– Not reported by scientists– Scientists are skeptical

• Ball Lightning– Often reported by scientists (and others

who are deemed credible and believable)

– Never photographed ! (confirmed to be authentic)

– Not produced in a laboratory and theoretical models are dubious (but a lot of effort has been put into studying this)

– A physiological effect ?


Sprites observed over a thunderstorm in Kansas in August, 2000


• Mission update #1


Life on Mars ?

• The Viking Lander had a biological experiment package on board to search for life

– If life is confirmed to exist on Mars, this would be a scientific discovery of EPIC proportions!

– In fact, some reason that this alone supports the Humans-to-Mars initiative

• ALH48001 – was there life on Mars in

the past ?


Labeled ReleaseExperiment:“Give them water”

Pyrolytic ReleaseExperiment:“Give them sunlight” Gas Exchange

Experiment:“Give them food”


Viking Results Summarized

• A key find came from the GCMS experiment– Mars has NO organic compounds– The surface of Mars is sterile

• The consensus opinion is that Viking found no evidence for life on Mars

• Better location?

– We know more about the surface of Mars now, perhaps a better site selection would help!


The Story of ALH84001

• A “SNC meteorite” found in 1984 in Alan Hills Antarctica

• Softball-sized meteorite weighing about 4 lbs.

• In a 1997 article in Science, David McKay indicated the meteorite showed evidence of primitive bacterial life on Mars


SNC Meteorites

• A separate class of meteorites. – Igneous rocks crystallized from

molten magma in a way which suggests they formed in a planetary-sized body, not an asteroid

– They show evidence of shock heating, presumably as a result of the impact which ejected them into space.

– Gas bubbles trapped in one meteorite, EETA79001, have a composition which matches the current Martian atmosphere

• Names after the first 3 places where they were found (Shergotty, Nakhla, Chassigny)


ALH84001 timeline

4.5 Billion years ago -- The original igneous rock solidified within Mars

3.6 - 4 billion years ago -- the rock was fractured. Water then permeated the cracks, depositing carbonate minerals and allowing primitive bacteria to live in the fractures.

3.6 billion years ago -- the bacteria and their by-products became fossilized in the fractures.

16 million years ago -- a large meteorite struck Mars, dislodging a large chunk of this rock and ejecting it into space.

13,000 years ago -- the meteorite landed in Antarctica, where it was discovered in 1984


The Story of ALH84001

• Simple organic compounds were found on the fracture surfaces

• Carbonate “globules” – look like mineral alterations

caused by primitive bacteria on Earth

– Concentric “rings” of different composition

– Magnetite was very pure• “Ovoids”

– may be fossilized remains of bacteria

– Extremely small• Smaller than even single cells

– Not life as we know it

globules

ovoids


• Where do we stand on this ? – The original authors still maintain that this is

evidence of life on Mars.– Most scientists believe that the evidence can

be explained by non-biological processes• Need additional evidence

• The future?– A sample-return mission would be important to

resolve the issue of life on Mars• Very expensive• A multinational plan for 2005 was scrapped due to

the back-to-back failures of 1999.

– The earliest launch of the next sample-return mission is 2014


Extrasolar Planets

• About 8 years ago, astronomers began finding extrasolar planets, or planets orbiting other stars– More than 200 have been

detected so far

• They are not actually seen, instead, their effects on their parent star are oberved


Methods of detecting extrasolar planets

• Astrometry (changes in the star’s location)

• Radial Velocity (changes in the star’s velocity)

• Transit method (dimming caused by a transiting planet)

• Other methods:– Pulsar timing, gravitational

microlensing, circumstellar disks


Habitable zone

• a region of space where conditions are favorable for life as it can be found on Earth (water can exist as a liquid)

• This distance is centered on


The recent discovery of a new extrasolar planet that is within the habitable zone of its parent star

It may be earth like – but the diameter (and hence the density) is not known without modeling


Final Exam• Format:

– 6 short answer questions (4 pts each)

– 38 multiple choice questions (2 pts each)

– Closed book, closed note, no electronic devices (including a calculator!)

– Bring a #2 Pencil

– You will have 2 full hours to take the exam

• What will it cover?– Mostly material discussed in the lectures (75%)– Reading (25 %)– 75% of the exam will be from Chapters 14-17– 25% from topics covered throughout the course

• A brief review of these follows


Final Exam

• What should you study?– Go over lecture slides– Go over questions at the beginning of each chapter– Go over key ideas and review questions at the end of

each chapter– Go over in-class activities, quizzes, and homework

(except for mathematical questions)• The solutions are on the website

A practice exam is now posted on the website


Final Exam: A brief review of comprehensive material (25% of exam)

• Chapters 1-4 : Basic Astronomy– The motion and position of objects in the sky

• Diurnal motion, retrograde motion• Reason for seasons

– Moon phases– Kepler orbits and gravity

• Chapter 5: The Nature of Light and Atoms– Wien’s Law– Stefan-Boltzman law– The Electromagnetic Spectrum– Kirchoff’s Laws (emission and absorption lines in

spectra)



• Chapters 7 and 8: The layout, nature, origin, age, and formation of the Solar System– Basic solar-system properties

• Terrestrial planets and gas giants• All planets orbit the Sun in the same direction and

in the same plane• Density of the planets

– The Solar Nebula– The nebular hypothesis of the formation of the solar

system



• Basic Planetary processes– Interiors and Surfaces– Review the “rules of thumb” discussed in the textbook

• p. 156 (in box 7-2)• p. 159• p. 161

– Planetary Magnetic Fields– Atmospheres

• Chapter 9: The Earth– Plate tectonics– Structure of the interior– Greenhouse effect



• Chapter 18: The Sun– Basic Structure (interior and atmosphere)

• Radiative zone – NOT radioactive zone!– Energy Source

• Sun-Earth connection– Sunspots and the sunspot cycle

• Sunspots are dim against the Sun, but still very bright!– What is a geomagnetic storm?– What is a cosmic ray?

• Chapters 10 and 11: The Moon and Mercury– Lots of craters – why?– Basic surface geology (highlands, mare)– No atmosphere – why ?– Synchronous rotation (due to tidal forces)



• Chapter 12: Venus– Why does it exhibit phases ? And why is it so bright?– Runaway greenhouse effect

• Chapter 13: Mars– Why is it at opposition every 2 years (nearly) ?– Evidence for Water – Atmosphere– Basic geology (northern vs southern regions)


Final Exam: A brief review of Chapters 14-17 (75% of exam)

• Chapters 14 : Jupiter and Saturn– Orbits– composition– Rotation

• Both are rapid and exhibit “differential rotation”– Oblateness (Saturn is the most oblate)– Features of the upper atmosphere

• Belts, and Zones, Giant Red Spot (Jupiter)– Interiors– Magnetic Fields

• Jupiter – extremely strong• Saturn – aligned with rotation axis

– Planetary Rings (formation, gaps, which planets have them? Saturn’s rings, etc.)



• Chapter 15: Jupiter and Saturn’s Moons– Galilean Satellites: A Solar system in

miniature– Io, Europa, Ganymede, and Callisto– Titan and Enceladus– Tidal forces (tidal heating of the moons)– Connection to the Jovian Magnetosphere

• Io torus



• Chapter 16: The Outer Worlds– Uranus and Neptune

• How were they discovered?• Why are they blue-green in color?• Uranus has an unusual tilt• Both have unusual magnetic fields

– Pluto• Discovery• Orbit• Charon• Kuiper-belt objects



• Chapter 17: Asteroids/Comets/Meteorites– Asteroid Belt– Kuiper Belt– Oort Cloud– Kirkwood Gaps– Trojan Asteroids– Asteroids shapes and brightness– “Rubble piles”



• Chapter 17: Asteroids/Comets/Meteorites (cont.)– Meteorites

• Stony, irons, stony-irons, carbonaceous chondrites

– Comets• Basic structure• Orbits• Meteor showers

ptys/astr 206life / exo planets 5/1/07 extraterrestrial life and … extrasolar planets

Documents

life exo planets

mars slide

extraterrestrial life

extrasolar planets

food slide

ball lightning slide

surface of mars

gcms experiment mars