Extraterrestrial Life, Astro/Geol 3300 MidTerm #2 April 12, :00-3:15pm Duane G125

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1 Extraterrestrial Life, Astro/Geol 3300 MidTerm #2 April 12, :00-3:15pm Duane G125 Name: SOLUTIONS Our next class, Tuesdat April 17, will be meeting at the Planetarium at 2:00. Directions: You have the entire 75 minutes from 2:00-3:15pm today to finish this exam. The total point total is 200. You can see the point value for each question labeled. The short and long answer will be graded with partial credit for work and/or partially correct answers. This test is open book and open note. Laptop computer, Kindles and ipads are allowed - BUT COMMUNICATION BETWEEN STUDENTS OR WITH ANYONE OUTSIDE THE ROOM IS STRICTLY FORBIDDEN! By signing and turning in this test you are bound by the University of Colorado Honor Code. Play fair! Multiple Choice. Simply circle the correct answer. (4 points each) 1. Which is not part of our 5-step requirements for life? a. Reproduction b. Genetics c. Organization d. DNA 2. Which of the following surface conditions makes the possibility of life on Venus so remote? a. runaway greenhouse effect from dense ammonia (NH 3 ) atmosphere b. extreme cold from the high albedo from dense sulfuric acid clouds c. thin atmosphere of hydrocarbons and nitrogen with no free oxygen d. thick atmosphere of CO 2 and proximity to the Sun e. enhanced volcanic activity created by impacts from asteroids 3. Which best characterizes the atmospheric make-up in the Miller-Urey experiment a. highly reducing H, CO 2, H 2 O, NH 3, CH 4 b. highly oxidizing H, H 2 O 2, N 2 O c. intermediate oxidation - H, CO 2, H 2 O d. rich in salts NaCl, SO 4 4. The Murchison Meteorite was important for what was found in it a. liquid water b. amino acids c. only left-handed chirality amino acids d. ATP e. segments of DNA 5. The outer edge of a simple Habitable Zone criteria is determined by? a. Where water freezes. b. Where water evaporates. c. Where water bears die. d. The orbit of Venus.

2 6. The primary current energy source for the moons at Jupiter is caused by? a. Differentiation b. Radioactive decay c. Tides d. Windmills! 7. Of the four largest moons at Jupiter, which is the most volcanically active? a. Io b. Europa c. Ganymede d. Callisto 8. Of the four largest moons at Jupiter, which is not locked in a resonance? a. Io b. Europa c. Ganymede d. Callisto 9. Name of the theory stating that periods of evolution are short and fast, followed by long spells of minimal change. a. Predation and Prey b. Punctuated Equilibrium c. Allopatric d. Mutation 10. If the Earth had no atmosphere, its surface temperature would be? a C b. -17 C c. 17 C d. 170 C 11. The polar caps at Mars are made of what? a. SO 2 frost. (silicon dioxide) b. CO 2 frost c. Snow (frozen water) d. A combination of b. & c. e. A combination of a. & b. 12. What effect will a slowly increasing luminosity over geologic time have on a star s circumstellar habitable zone? a. No effect, because as the star ages planetary orbits increase b. The habitable zone will remain the same as planets change their atmospheric compositions c. high radioactivity from planetary cores will keep the surfaces warm d. the habitable zone will migrate away from the star e. planetary albedos will decrease to compensate

3 13. We find what liquid on the surface of Titan? a. CO 2 b. H 2 O, c. ammonia d. methane e. N 2 Place stuff in order. Place numbers next to the list of answers to place them in order according to the question s directions (4, 4 and 5 points). 1. From smallest to largest: a. Eukaryotic cell (4) b. Prokaryotic cell (3) c. An average protein (2) d. A Silicon Atom (1) 2. From ancestor to descendent: a. A horse (4) b. The first archaea (1) c. The first eurkaryote (2) d. The first multi-cellular organism (3) 3. From furthest in the past until the closest to the present (oldest to youngest) (2) a. The life that existed at Apex Chert (1) b. The age of the Isua rocks in Greenland where we find Carbon isotope signs of life (3) c. The era of Banded Iron formations in which we find signs of photosynthetic cyanobacteria (4) d. The age of the Burgess Shale Community fossils (5) e. The era of the Dinosaurs Short Answer. One sentence should be enough, but you may use ONLY two or three sentences MAXIMUM, answer the following questions. On some mathematical questions, I am interested in the work you did to get the answer and mathematical answer (7 points). 1. If an alien landed on Earth who had cells that replicated using DNA, what would be the possible implications? (Not that the media would freak out or the world would end, rather what would it tell us about this alien, where it came from, and life in the Solar System) It came from Earth explaining the similarities (Panspermia) (or) Life generically evolves towards using DNA- possibly similar initial environments+materials (or) Life on Earth was seeded by this Alien s life via Panspermia 2. What is the evolutionary advantage of DNA having two strands? It is more stable than one single strand of RNA -> less mutations.

4 3. What evidence is there that Mitochondria were in fact independent organisms at one point? -It has its own DNA -It has a double membrane 4. Mercury is in an odd spin-orbit state. It s orbit take 88 days, and its rotation takes 59 days. Its day (the time it takes for the Sun to do one lap) then ends up being quite long. Describe this scenario feel free to use illustrations. This image shows the rotation of Mercury during its orbit. The light side isn t showing what is illuminated, rather it is showing separate halves of the planet so you can see the rotation during the orbit. To see the entire Mercury-Day, we would need one more orbit, rather we see here. -first orbit of Mercury, -first 1 1/3 rotation of Mercury -first half day : from Noon to Midnight 5. We discussed 3 ways that some essential polymers could have originated on earth. Name and quickly describe each method. 1. Miller-Urey Style organic debris mixing in tidal pools or ponds 2. Delivery from ET sources direct from comets/asteroids 3. At Hydrothermal Vents where organics mix at volcanic spots in the ocean flooer with temp gradients to help things combine. 6. What are cell membranes made from and what property of this material probably helped in the construction of the first cell membranes. Lipids have hydrophilic and hydrophobic ends.. which naturally align with each other in a polar solvent like Water. This helps them eventually come together in a bilayer that can then encircle important material.

5 7. What is the difference between a Canal and a Channel? How did this affect the early scientific thoughts about Mars? Canal is man-made, but Channel is natural made. Some mis-transalted canali into Canal, which implied man-made features on Mars. Fast-forward until the 90 s and the triumph called Mars Attacks is created. 8. Quickly explain the importance of the Ribozyme discovery namely, what is unique about what they do? This discovery found that ribozymes could both carry genetic information (like RNA/DNA) and catalyze reactions (like enzymes) 9. What are the main advantages of life forming at Hydrothermal Vents (I can think of three or four clear answers)? 1. Protection from harmful UV radiation 2. Long timescales 3. Hot temperatures to combine things 4. Cool temperatures to allow proteins to survive 5. Healthy source of important organics 10. What are the main advantages (2-3 clear ones) of Carbon being the base element of life instead of Silicon? 1. Abundant (more than Silicon, much more) 2. Smaller (strong bonds) 3. Lighter 11. The peppered moths of England are a textbook case of evolution by natural selection. a. Describe their evolution and the causes for it. The population went from nearly all white to nearly all black during the time that trees were being colored by soot from the Industrial Revolution. As the trees change color the white moths were more susceptible to be hunted (and eaten). Those with the desireable trait of being dark were more likely to survive and pass on their heritable traits. b. We listed two essential criteria for evolution by natural selection. What were they and how do these moths fit the criteria. 1 Variation in a population heritable traits 2 Overproduction

6 Long Answer: Please take your time and construct a coherent answer in the space allotted. 1.) Explain how Mars has evolved over it history. You will need to comment on the following aspects: (36 points) a.) How might an early Mars have looked - in terms of its water content and its early atmosphere? Mars likely outgassed significant CO2 early in its history while it was still very geological active, resulting in a likely reasonably heavy atmosphere one which probably could have supported anywhere from some to significant liquid water. b.) What evidence is there for past water on Mars? How much water? -Gullies -Outflow channels -Hydrated minerals like (Haematite blueberries) and Jarosite -Frozen water below the surface -Polar caps made of ice (and CO2) c.) Mars transitioned and evolved to look like the Mars of today. What was likely the main process behind this transition? When do we think this happened? Mars small size means it has lower gravity AND less internal heat initially from its accretion/differentiation/radiogenics. These two mean that it lost its dynamo around 4 Gyr ago, leading to the loss of its magnetosphere, which then couldn t protect its atmosphere. Being small its atmosphere was then easy pickings for the Solar Wind. d.) Why is Water so important as a solvent what properties does it have that we don t always find in liquid solvents -Abundant H and O -Large range of Temperature as a liquid -High temperature liquid (reactions go faster) -Lower density as a solid (ice) then as a liquid -Polar -High surface tension and Cohesion

7 2. The RNA world scenario is a leading theory for the origin of life. (22 points) a.) First tell me what relatively recent (and local) discovery was the catalyst for this idea and why it is important regarding the origin of life? RIBOZYMES. These are the chicken and the egg, something that can carry genetic information and catalyze reactions. b.) Why is RNA a more likely precursor than DNA? It is simpler, having only one strand. Also, the above answer and other results find that RNA can self-replicate in some situations, which is way easier than the complicated process used for DNA. c.) Finally evaluate whether or not RNA world is compatible with the ideas surrounding life originating at Hydrothermal vents. Sure. A good argument for or against would work here. RNA World really is focused on the first genetic-carrying self-replicating molecules. This would really be the step into organisms that can reproduce and pass on heritable traits. Life forming at Hydrothermal Vents is attractive for how it could be hospitable for polymers to start forming in the hot, organic rich, region around a vent and then collect nearby in the cool waters of the Ocean. This is a step before something like RNA World, and may be the ideal place for the first self-replicating bodies to start forming and living.