ASTR2040_HW5_Assignment

M/W/F 10:10-11:00 AM H OMEWORK #5 L IFE IN THE U NIVERSE T HE N ATURE OF HABITABILITY ASTR/GEO 2040 D UE 11/10 BY M IDNIGHT N AME _____________________________ 1 I NTRODUCTION This homework assignment focuses on Chapters 8—9 and the beginning of Chapter 10 in the textbook covering the search for life on Mars and the icy Jovian moons in the outer Solar System, as well as the nature and evolution of habitability. Other things to keep in mind – For any question that asks for a quantitative answer, be sure to show all of your work! Lots of partial credit is available for showing work even if the final answer is incorrect. If a question asks for specific units, be sure to put your answer in those units. Finally, many problems have multiple parts or ask for multiple answers – make sure to read all parts of a problem to avoid missing something. ______________________ 1. L IFE ON M ARS There have been many previous claims of life on Mars—none of them have been unambiguous and many have been proven to be completely false. (10 points total) (a) What are three pieces of evidence that we discussed in lecture that have been used to claim that there is or has been life on Mars? (Hint: look back at Lecture #26 from 10/27) (b) For one of these pieces of evidence , how was this claim of Martian life ultimately discredited? Imagine that in the future we find unambiguous evidence for microbial life on Mars. (c) How could we know that this life is of independent origin? In other words, name one property of life that we have covered in class that could indicate that this life originated on Mars and not on Earth? 1 Mars has evidente of liquid water 2 methane spikes can be a byproduct of microbial activity 3 pretense of organic compounds The organic compounds found in the soil on mars could be a result of meteroite activity impacts and not biological The genetic makeup if the genetii code is different than earth based lifeforms it would suggest that life evolved independently on Mars

N AME _____________________________ H OMEWORK #5 2 (d) Describe one process by which life on Earth and Mars could share a common origin. ______________________ 2. I CY M OONS OF THE O UTER S OLAR S YSTEM Despite their great distance from the Sun, several Jovian moons are considered excellent candidates in our search for extraterrestrial life in the Universe. (12 points total) (a) Why do these Jovian moons have lower densities on average than the terrestrial planets? (Hint: think about the title of this problem!) (b) Describe two pieces of observational evidence that support the presence of subsurface liquid water oceans on Europa. (c) Why is Europa considered a superior target for the search for life compared to Ganymede? Be specific—Give one reason for Europa and one reason against Ganymede . (d) Based on energy considerations, do you think the icy Jovian moons could support a total biomass comparable to that of Earth? Why or why not? (e) Between Titan or Enceladus – both moons of Saturn – which do you think is more likely to be habitable and support life? Justify your answer! panspermia suggests that life could orginate from another planet through transfer of microorganisms through meteorites Because they are primarily composed of ices water ice methane ice ammonia ice These are less dense than rock metal 1 The Galileo spacecraft detected a magnetic field around europa this suggests a conduct layer of fluid beneath the surface Z Surface shows I evidence I easier access to subsurface ocean Europa has minner ice stiffs sea ice resemble Ganymede's subsurface is sandwhicded its unlikely The oceans could potentially support microbial life the surfaces couldn't support a large complex ecosystem They recieve less energy life because it has an active plume of and chemical water vapor and organic molecules this reaction stria indicates the pretense of a subsurface support life ocean Titan has too rich of an would be slow because t atmosphere wi nitrogen methane the temp

N AME _____________________________ H OMEWORK #5 4 ___________________ 4. M ULTIPLE C HOICE A few multiple-choice questions to test your understanding of the material covered in lecture. Each correct answer is worth 1 point for 6 points total. (4.1) Which of the following fundamental properties of Mars could explain why it once had a global magnetic field but later lost it? (A.) its small size (B.) its larger distance than Earth from the Sun (C.) a rotation rate that is slightly slower than Earth’s (4.2) The moons of Saturn have large amounts of ammonia and methane ice, while those of Jupiter do not because… (A.) Jupiter’s strong magnetic field prevents ice formation (B.) methane and ammonia only come from comets that exist in the Oort cloud (C.) the temperature is lower at Saturn’s distance from the Sun, which means that ammonia and methane could condense there but not at Jupiter’s distance (4.3) The primary source of internal heat for Io is… (A.) tidal heating from Jupiter (B.) radioactive decay (C.) the greenhouse effect (4.4) Which statement about synchronous rotation is true? (A.) it can develop only on moons that are born with slow rotation (B.) it occurs commonly as a result of tidal forces exerted on moons by their parent planets (C.) it can develop only on moons with liquid oceans (4.5) Photosynthesis is an unlikely source of energy on Europa because… (A.) Jupiter emits most of its light in the infrared range (B.) sunlight at the distance of Jupiter is too weak to provide much energy (C.) there is no soil for plants to grow in (4.6) A planet that is not within a habitable zone cannot have… (A.) life (B.) subsurface oceans (C.) abundant liquid water on its surface or or or as