Astronomy 330 Take Home Midterm

•! Will email it to everyone after class Thursday. This class (Lecture 12): –! 50%: 4 short (few paragraphs) essays Life in the Solar System –! 50%: 1 larger (~1-2 page) essay (with definition terms) Next Class (Thursday): •! Must be typed, not handwritten. Life in the Solar System •! Will cover material up to and including Thursday. Se-Joon Chung •! It is a closed notes exam (honor system!). Nicholas Langhammer •! You can make 1 page of notes for use during the exam. HW 5 is due next Tuesday (special date)

Music: We Are All Made of Stars– Moby

HW 2 Outline

•! Jeremy Morton •! Ne is broken into 2 terms http://www.thetruthbehindthescenes.org/ •! How got Mooned 2011/09/15/denver-international-airport-alien- •! Early Earth connection-decoded/

•! Alison Melko http://www.ufoabduction.com Drake Equation n Frank e That’s 16 planetary systems/year Drake Complex term, so let’s break it into two terms:

–! np: number of planets suitable for life per planetary system

–! fs: fraction of stars whose properties are suitable for life to develop on one of its planets

N = R* ! fp ! ne ! fl ! fi ! fc ! L http://nike.cecs.csulb.edu/~kjlivio/Wallpapers/Planets%2001.jpg # of # of Star Fraction Fraction advanced Earthlike Fraction Fraction Lifetime of formation of stars that civilizations planets on which that evolve advanced rate with commun- we can per life arises intelligence civilizations planets icate contact in system our Galaxy today 20 0.8 planets/ life/ intel./ comm./ yrs/ stars/ systems/ system planet life intel. comm. yr star

Kepler’s Estimate Our Solar System Terrestrial planets and Gas Giants… but how many are valid

planets/moons for np?

The Kepler team estimated that at least 5.4% of all stars host Earth-like planets and that at least 34% of all stars have planets. X

Others using the Kepler data estimated 1.4 to 2.7% of all -like stars are expected to have earth-like planets within the habitable zones of their stars-- or two billion in the Milky Way! But, do we need Earths for life? http://arxiv.org/pdf/1102.0541v1 Earth-Moon Comparison Formation of the Earth

•! Earth formed from planetesimals in the circumstellar disk. •! Was hot and melted together. Radius 6378 km Radius 0.272 Earth •! The biggest peculiarity, Surface gravity 9.8 m/s2 Surface gravity 0.17 Earth compared to the other Mass 6.0x1024 kg Mass 0.012 Earth Distance to Sun 1.5x108 km Distance to Earth 384,000 km planets, is the large Year 365.2422 days Orbital Period 27.3 days moon. Solar day 1 day Solar day 27.3 days

Feb 7, 2008 Astronomy 330 Spring 2008

A Double World The Moon

Why a “double world”? Earth and The Moon's surface –! Most moons are tiny Moon together is barren and dead compared to the planet from •! The Moon is over 25% the Voyager 1 –! No water, no air, some diameter of Earth (1977) water ice. •! Jupiter's biggest moons are about 3% the size of the –! No life!! planet –! The Moon is comparable to the terrestrial planets •! Well, mostly dead. •! About 70% the size of Mercury •! Nearly the same density as The Moon: Mostly Dead Formation of the Moon: Smack

•! Well, mostly dead. •! Collision of Earth with a Mars-sized •! Recent results show body early in the solar some new (50 million system’s history years new) regions •! -rich core of (called graben) that are the impactor free of cratering. sank within Earth •! So interior may still •! Earth’s rotation have significant molten sped up component •! Remaining ejecta thrown into orbit, coalesced into the Moon •! http://www.youtube.com/watch?v=ibV4MdN5wo0&feature=related

Why is this a good hypothesis? Moon Impact on Life?

•! The Earth has a large iron •! Some think that our large Moon is very important core (differentiation), but the for life on Earth. moon does not. –! Tides! Important to move water –! The debris blown out of in and out of pools. collision came from the rocky –! Stable Axial Tilt: 23.5 deg mantles offset from the collision –! The iron core of the impactor –! Metals! Heavy elements at merged with the iron core of Earth’s surface may be from Earth core of impactor. •! Compare density of 5.5 g/cm3 to 3.3 g/cm3— the moon

http://www.flatrock.org.nz/topics/odds_and_oddities/assets/extreme_iron.jpg lacks iron. http://www.michaelbach.de/ot/sze_moon/index.html Moon: Impact Implications Planetary Differentiation •!! Hot, Hot, hot, Hot! hot. Even if the moon theory is incorrect, other smaller bodies were playing havoc on the surface. •! When they impact, they release kinetic energy and gravitational potential. •! In addition, some of the decaying radioactive elements heated up the Earth– stored supernova energy! •! The planetesimals melt, and the Earth went through a period of differentiation. http://www.udel.edu/Biology/Wags/wagart/worldspage/impact.gif

Differentiation: Early Earth Iron Catastrophe

•! Average density of Earth •! No atmosphere is 5.5 g/cm3 •! No water •! Average density on the surface is 3 g/cm3 •! High temp •! So, something heavy •! No life……. must be inside •! Big rocks keep •! When the Earth formed it was molten falling on my head… –! Heavy materials (e.g. iron, nickel, gold) sank –! Lighter materials (e.g. silicon, oxygen) floated to the top

http://www.black-cat-studios.com/catalog/earth.html Question Structure

Which of the following does NOT well describe the early Earth? •! Luckily, not all of the iron sank to the center, else we would be still in the Stone Age. a)! So hot that the surface had molten rock. Outer Core •! Temperature increases as you b)! There was no water. go deeper underground. From Inner Core c)! The surface kept getting hit by really, really big rocks. around 290 K on surface to Mantle d)! The oxygen rich atmosphere caused quick oxidation nearly 5000 K at center. (rusting) of iron-rich rocks –! Heated by radioactive decay Crust e)! No chance of life at this stage. –! Supernovae remnants •! Earth’s magnetic field is established early on.. after the iron catastrophe… good for life.

The Crust Today’s Earth Surface

•! Outside layer of the Earth (includes oceans) floats on top •! 70% of the Earth's of still hot interior surface is covered –! About 50 km thick with water –! Coldest layer – rocks are rigid –! Ocean basins •! Mostly silicate rocks –! Sea floors are young, –! Made of lighter elements like silicon, oxygen, and aluminum none more than •! Oxygen and water are abundant 200 million years old •! Excellent insulator •! 30% is dry land – Continents –! Keeps the Earth’s geothermal heat inside! –! Mixture of young rocks and old rocks –! Up to 4.2 billion years old Geologically Active Surface Recycling Bio-elements

•! The young rocks on •! From gravity and radioactivity, the core stays hot. the Earth's surface •! This allows a persisting circulation of bioelements through indicate it is continental drift— melting of the crust and re-release geologically active through volcanoes. •! Where do these rocks •! Otherwise, certain elements might get locked into sediment come from? layers– e.g. early sea life. –! Volcanoes •! Maybe planets being formed –! Rift valleys now, with less supernovae, would not have enough –! Oceanic ridges radioactivity to support •! Air, water erode rocks continental drifts and volcanoes. •! The surface is constantly changing http://www.pahala-hawaii.com/j-page/image/activevolcanoe.jpg

The Earth’s 1st Atmosphere The Earth’s 1st Atmosphere

•! The inner disk had most gases •! The interior heat of the Earth helped blown away and the proto-Earth with the Earth’s early atmosphere. was not massive enough to capture •! Volcanoes released gases (water vapor these gases. and CO2) •! Any impacts (e.g. the moon), •! Another scenario is that impacted would have blown any residual comets released – water (H O), atmosphere away. 2 carbon dioxide (CO2), and Nitrogen (N2) •! The first atmosphere was probably – the first true atmosphere. H and He, which was lost quickly. •! The water condensed to form the oceans and much of the CO2 was dissolved in the oceans and incorporated into sediments– such as calcium carbonate (CaCO3).

http://www.udel.edu/Biology/Wags/wagart/worldspage/impact.gif http://www.fli-cam.com/images/comet-liner.jpg Our Atmosphere This New Planet

•! Rocks with ages greater than •! Mostly oceans and some solid land (all volcanic). 2 billion years show that there was •! Frequent impacts little or no oxygen in the Earth’s of remaining atmosphere. planetesimals •! The current composition: 78% (ending about nitrogen, 21% oxygen, and trace 3.8 billion years amounts of water, carbon dioxide, ago). etc. •! Impacts would •! Where did the oxygen come from? have sterilized •! Cyanobacteria made it. the young Earth– http://www.uweb.ucsb.edu/~rixfury/conclusion.htm Mass extinctions and –! Life on Earth modifies the Earth’s maybe vaporized any oceans (more comets?). atmosphere.

http://www.agnld.uni-potsdam.de/~frank/Images/painting.gif

This New Planet Question

The Earth’s first atmosphere was

a)! much like today’s atmosphere, but older. b)! Trick Question. There was no atmosphere. c)! likely just H and He, and blown away quickly. d)! made from comets. e)! a combination of volcano gases and comet collisions. Water Water

•! Water is a key to life on Earth. •! Primary role as a solvent •! Primary constituent of life– “Ugly bags of mostly –! Dissolves molecules to bring nutrients and remove wastes. water” Allows molecules to “move” freely in solution. –! Must be in liquid form, requiring adequate pressure and –! Life is about 90% water by mass. certain range of temperatures. •! http://www.youtube.com/watch?v=LAlqp0_a0tE •! This sets a requirement on planets, if we assume that all life requires water. •! Does it?

Water as a Solvent Example: Dissolving Table Salt

•! The water molecule is “polar”. The oxygen atoms have The partial charges of the water molecule are attracted to the Na+ and Cl- more build-up of negative charge than the hydrogen. This ions. The water molecules work their way into the crystal structure and between the individual ions, surrounding them and slowly dissolving the allows water molecules to link up, attracted to each other. salt. •! In this way, water attracts other molecules, surrounds them and effectively dissolves them into solution.

http://www.visionlearning.com/library/module_viewer.php?mid=57 Water: Our Liquid Friend Keeping it Useful: Atmosphere

•! A very good temperature buffer •! Need to have enough pressure to keep water from boiling –! Absorbs significant heat before its temperature changes away at low temperature –! When it vaporizes, it takes heat with it, cooling its –! Cooking at higher elevation requires more time. Boiling point lowered: water doesn’t original location get as hot. –! If pressure too low, water goes directly from • It floats. ! ice to vapor (like dry ice CO2) –! Good property for life in water. •! On the other hand, high pressure may –! Otherwise, a lake would freeze make life more difficult to form. bottom up, killing life. •! In addition, the range of temperature for –! By floating to the surface, it can Earth based complex life is less than 325K. insulate the water somewhat.

http://whatscookingamerica.net/boilpoint.htm

Keeping It Warm, but not too Warm Greenhouse Explained

•! What controls a planet’s temperature? –! The amount of light received from its star. –! The amount of energy the planet reflects back. –! And any Greenhouse effects of the planet.

http://www.solcomhouse.com/Greenhouse_Effect.gif Habitable Zones– Keeping It Warm, but not too Warm Are you in the Zone? •! Long living star •! Earth’s greenhouse effect •! Planets with stable orbits (thus stable temps) raises the temperature by •! Liquid Water Mars about 15%. •! Heavy Elements– C, N, O, etc. •! Given a star’s luminosity, a •! Protection from UV radiation Earth range of acceptable Venus temperatures translates into a range of distances to the star. Mercury •! This range is called the star’s habitable zone (HZ), as planets in this range have temperatures suited for life. •! Only a rough guideline. The Sun 0.5MSun star

http://www.solcomhouse.com/Greenhouse_Effect.gif

Galactic Habitable Zone Question

The Greenhouse effect •! Likewise the galaxy has regions that are a)! will destroy our planet. better suited to life. b)! will hopefully stop this crazy winter. •! In the inner regions of c)! keeps the Earth warmer than it would be otherwise at its our galaxy, distance from the Sun. supernovae are too d)! is all Man-Made. frequent. e)! keeps the Earth colder than it would be otherwise at its •! In the outer regions, distance from the Sun. there are too few metals.

http://astronomy.swin.edu.au/GHZ/GHZmovie.html The Sun’s Variation The Sun’s Variation

•! As the Sun ages, it gets slightly brighter. •! There is evidence that the Earth did nearly freeze over– 2.8 billion years •! When it was younger, its luminosity was 70% ago and 700 million years ago. current values. •! Probably changes in the Greenhouse gases. •! A young Earth should have been 20K colder– •! This implies that the habitable zone iceball! can vary with time, thus the real –! During our ice ages, the habitable zone is smaller than shown temperature only changed before? by about 1%! •! Some have postulated that real zone is only 0.95 to 1.01 AU! If the Earth were 1% farther away– Iceballed. http://www.soest.hawaii.edu/gerard/GG108/images/bylot.jpg http://www.cherishclaire.com/iceball.htm And np would be very small ~ 0.1.

Earth’s Atmosphere: Earth’s Atmosphere:

Trapping CO2 for Fun and Profit Trapping CO2 for Fun and Profit •! Most recent studies suggest an efficient planet negative-feedback mechanism (like a thermostat). •! Negative feedback process –! Increase in temperature: evaporation of oceans, –! CO2 cycles from atmosphere (greenhouse gas) and oceans (buried sediment especially carbonate rock). more rainfall, more weathering and CO2 reduction, so decrease in temperature. –! CO2 in atmosphere: temporarily dissolved CO2 in rainfall reacts with weathered rocks, trapping it. –! This negative feedback stabilizes the Earth’s temperature.

http://www.wildtech.org/images/feedback.gif http://www.wildtech.org/images/feedback.gif Life Adds to Feedback Life in the Solar System?

•! Life increases the •! We want to examine in more detail the backyard of weathering of rock. humans.

•! Some have proposed that •! What we find may change our estimates of ne. life also stabilizes the planet temperature. •! Regardless, the negative feedback helps with the habitable zone, so we can estimate perhaps np is more around 1– more Earth chauvinism?

Earth – Venus comparison What We Used to Think

Venus must be hotter, as it is closer the Sun, but the cloud cover must reflect back a large amount of the heat.

In 1918, a Swedish chemist and Nobel laureate concluded: •! Everything on Venus is dripping wet. Radius 0.95 Earth •! Most of the surface is no doubt covered with swamps. Surface gravity 0.91 Earth Venus is the hottest •! The constantly uniform climatic conditions result in an Mass 0.81 Earth entire absence of adaptation to changing exterior conditions. planet, the closest in Distance from Sun 0.72 AU size to Earth, the closest Average Temp 475 C •! Only low forms of life are therefore represented, mostly no in distance to Earth, and Year 224.7 Earth days doubt, belonging to the vegetable kingdom; and the the planet with the Length of Day 116.8 Earth days organisms are nearly of the same kind all over the planet. longest day. Atmosphere 96% CO2 http://www.daviddarling.info/encyclopedia/V/Venuslife.html Turns Out that Venus is Hell Our “Twin”

•! The surface is hot enough to melt lead •! Always covered in thick clouds of CO , which • There is a runaway greenhouse effect 2 ! make it the hottest planet •! There is almost no water in the Solar System. •! There is sulfuric acid rain •! Not a place to visit for Spring Break. •! Pressure on surface is 90 times that on Earth– like 1 km under the sea

http://antwrp.gsfc.nasa.gov/apod/ap960923.html

Our “Twin” Soviet Satellites on Venus •! Often called the morning star or the evening star. 3rd brightest object in the sky. •! Often mistaken for a UFO. •! Retrograde rotation – Sun rises in west •! No moons, no magnetic field

Mostly Basalts-like rocks, indicative of volcanoes http://antwrp.gsfc.nasa.gov/apod/ap960923.html The Venusian Surface Revealed Surface of Venus: Radar

•! We can’t see Venus’ surface in visible light, clouds block the view •! Magellan’s Radar showed the surface •! Most of surface is smooth lava flows •! Many large volcanoes •! Probable ongoing http://www.solarviews.com/cap/venus/vidven1.htm volcanism

Venus: surface features Impacts on Venus

•! Venus has about 1,000 craters, often clustered •! No trace of heavy 10,000 km bombardment •! Cratering rate indicates Venus’ surface about Maxwell Montes (65N 5E) 500 million yrs old (Highest mountain range in the solar system • Why? 11km high– Everest is 8km) ! –! Possibility: Extreme temperatures soften rock, making the surface subject to catastrophic volcanic upheaval

http://www.geology.smu.edu/~dpa-www/venus.html Venus’ Interior Runaway Greenhouse

•! Venus’ size and •! On Earth, greenhouse density are roughly Core gasses insulate us equal to Earth’s –! Keep Earth 35 K –! Indicates iron core of warmer than it would be similar size otherwise •! No magnetic field •! On Venus, massive –! Very slow rotation - amounts of CO2 keep it 243 Earth days incredibly hot –! Almost 300 K warmer! Crust Mantle –! The hottest planet in the Solar System

What Happened to Venus? Why So Different?

•! It really should have been more like Earth, but the atmosphere is much different. •! Earth’s carbon is locked up •! Earth’s atmosphere is mostly O2 from life, but early Earth was N. –! Dissolved in the oceans –! Locked into rocks and life •! Earth and Venus have similar amounts of carbon & nitrogen, but…

•! Venus’ carbon is in its atmosphere –! Too close to the Sun for liquid water –! No oceans to trap the carbon dioxide –! No life to process the carbon into sedimentary rocks http://www.digitalart.ab.ca/art/ren/images/birth-of-venus.jpg http://www.edgechaos.com/MECA/WALLART/VR89/venus.jpeg What Happened to Venus? Life on Venus?

•! Apparently Venus lost its H2O– no oceans and no •! Surface is far too hot sediments. –! If lead is liquid, think of what heat would do to •! Probably the atmospheric temperature was hot complex organic polymers enough for water to travel high –! No cooler polar regions exist enough to be broken apart by UV •! Heat is uniform! radiation, the H was lost and the O •! But, high in the clouds it should be cooler?! reacted with something else. •! Maybe life can still exist in •! Irreversible procedure! the clouds? •! Which is why greenhouse effect is •! At 50 km up, the temperature is worrisome here too! not too hot and the pressure is •! The Earth traps water vapor in the 1 atmosphere. cool tropopause at 14km.

http://photos1.blogger.com/blogger/4103/1148/1600/Venus%20Wimbeldon05.jpg

Chemical Disequilibrium Life on Venus?

•! High clouds in the atmosphere contain •! One possibility is that microbes living in the clouds could chemicals that hint at the presence of be combining sulfur dioxide with carbon monoxide and some kind of biological activity. possibly hydrogen sulphide or carbonyl sulphide in a metabolism similar to that of some terrestrial micro- •! Hydrogen sulfide and sulfur dioxide - two organisms (extremophiles). gases that react with each other– exist in •! Given that the temperature on Venus was once much the clouds. cooler, there may once have been oceans on the planet. Life –! So, something may be producing them. could have started there and retreated to stable niches once the runaway greenhouse effect began. •! Hardly any carbon monoxide, which •! Maybe a mission to scoop up some atmosphere? should be there. –! So something may be removing CO.

http://www.manson-valley.de/fotogalerie/manson/images/acss/acss_32.jpg Earth – Mars comparison What we used to think.

•! Similar to the Earth in many ways. •! Life was argued to exist on Mars. •! The astronomer Schiaparelli announced Radius 0.53 Earth that he saw regular linear Surface gravity 0.38 Earth markings on the surface, Mass 0.11 Earth which he named canali. Mars has the Solar Distance from Sun 1.5 AU • Technically, in Italian System’s largest Average Temp -63 C ! Volcano, Olympus Max Temp 20 C means channels, but it Mons – 27 km tall. Year 687 Earth days was mistranslated to canals. Length of Day 24 hours 39 minutes

Atmosphere CO2 95%

Percival Lowell’s Canals

•! Evidence for intelligent life? •! Mapped the civilization. •! Influenced culture. The Martian Atmosphere The Surface of Mars •! 95% carbon dioxide •! Mars is a desert! •! Atmospheric pressure 0.6% of Earth’s – •! Large daily and seasonal •! Iron oxide in soil gives reddish cast. like 40 km altitude on Earth swings in surface !!Too thin for significant greenhouse temperature effect. !!Pressure is too low for liquid water. •! Not protected by a global like Earth’s

http://www.grc.nasa.gov/WWW/PAO/html/marspath.htm

Water on Mars Liquid water on Mars? •! Water erosion features visible from space •! There is water on Mars •! Atmospheric pressure too low for liquid water –! North and south to exist

polar caps (mostly CO2) •! Perhaps at some point in the past? –! Some water vapor in the air –! Frost on rocks –! Clouds (ice crystals)

•! No liquid water now “Islands”

Valley networks Erosion Features Flood erosion New Water? The Surface of Mars: Opportunity

http://antwrp.gsfc.nasa.gov/apod/ap040303.html

Roving on Mars

Roving on Mars: Spirit and Opportunity find evidence of ancient liquid water

http://antwrp.gsfc.nasa.gov/apod/image/0403/ emptynest_opportunity_big.jpg Feb 26, 2008 Standing Water on Mars Mars Missions Now • The new data from the rovers are highly suggestive of ! •! Mars Reconnaissance ancient standing water on the Meridiani Planum. Orbiter •! 3 pieces of evidence: –! Studying the –! Physical appearance of rocks and climate of Mars –! Rocks with niches where crystals appear to have grown –! Look for ancient sea –! Rocks with sulfates left after the water evaporated shores •! Is it a former sea floor or just an area that had ground- –! Survey potential water? landing sites

El Capitan

Mars Missions Now Mars Missions Now •! Phoenix –! Analyze water ice at Mars’ north pole •! Phoenix –! Confirmed water ice on the surface of Mars –! Sublimates too slowly for dry ice (CO2)

http://www.nasa.gov/mission_pages/phoenix/images/ http://www.nasa.gov/mission_pages/phoenix/images/ press/PSP_008591_2485_RGB_Lander_Inserts.html press/PSP_008591_2485_RGB_Lander_Inserts.html Mars Missions Now Mars’ Watery Past

•! Phoenix –! Blobs on lander legs –! Blobs merge (Sol 8 & 31) –! Liquid! –! Saltwater most likely

http://www.planetary.org/blog/article/00001890/