KEY Planetary Sciences Section 2 Midterm Examination #1 9:30-10:45 a.m., Tuesday, September 17, 2013

Transcription

1 KEY Planetary Sciences Section 2 Midterm Examination #1 9:30-10:45 a.m., Tuesday, September 17, 2013 INSTRUCTIONS: There are 35 multiple-choice questions, which are worth 2 points each. The last two questions (#36 and #37) are essay questions, and are worth 15 points each. Mark your multiple-choice answers on this test and on the scantron sheet. CLOSED BOOK, CLOSED NOTES, NO ELECTRONIC DEVICES. 1. According to Kepler's second law, l A. the Moon moves fastest in its orbit when it is near periapse m B. the Moon appears largest when it is rising or setting m C. the Earth and the Moon mutually orbit a common barycenter m D. it always takes a spacecraft 8 days to orbit from Earth to Moon m E. the Moon rotates about its axis and orbits Earth with the same period 2. An astronomical unit (AU) is m A. the radius of the heliosphere l B. the semimajor axis a of the Earth's orbit m C. the distance from the ecliptic plane to the galactic plane m D. the mean distance from the Sun to the furthest planet, Pluto m E. the semimajor axis a of Mars' orbit 3. The direction of a prograde orbit is m A. perpendicular to the ecliptic plane l B. counterclockwise, as viewed from above the Sun's north pole m C. orthogonal to the galactic plane m D. usually dependent on the orbit's angular momentum m E. similar to the orbital motion of Halley's comet during the 1986 visit 4. Figure 1 shows the orbit of a comet around the Sun (central dot). Two orbital distances are shown in AU. What is the eccentricity e of the comet's orbit? m A. e = 2/6 l B. e = 1/2 m C. e = 1/6 m D. e = 6/2 m E. e = 1/3 5. Referring to Figure 1, what is the period T of the comet's orbit? m A. T = 2 years m B. T = 4 years m C. T = 6 years l D. T = 8 years m E. T = 36 years 6. Spacecraft are sometimes placed at the Sun-Earth L 1 point because m A. they will stay there, farther from the Sun than the Earth is, for many months m B. that is the most efficient orbital path to get from Earth to Venus m C. that is the most efficient orbital path to get from Earth to Mercury m D. that is the most efficient orbital path to get from Earth to the Sun l E. they will stay there, closer to the Sun than the Earth is, for many months Page 1 of 6

2 7. In Figure 2, the curve from Earth to planet A to planet B shows m A. the fastest orbital path from Earth to planets A and B m B. a single Kepler orbit that goes from Earth to planet B m C. a Hohmann transfer orbit from Earth to planet B l D. a path from Earth to planet B using a gravity assist from planet A m E. a trajectory from Earth to Moon (B) with a rocket burn at planet A 8. A planet moves slowest in its orbit when it is at m A. inferior conjunction m B. quadrature m C. periapse l D. apoapse m E. superior conjunction 9. The solar wind is m A. ultraviolet light emitted by the Sun's corona m B. high-speed zonal gas flow circulating around the Sun's equator m C. what causes flags on the Moon to "blow" m D. about 1.4 watts per square meter at the Earth's orbit l E. plasma ejected from the Sun at 450 to 600 km/second 10. The solar constant is m A. a synonym for the astronomical unit m B. the emission rate of the Sun at wavelengths greater than 1 µm m C. the rate of consumption of helium at the Sun's center m D. the same as the summer or winter solstice l E. about 1.4 kilowatts per square meter at the Earth's orbit 11. The first artificial Earth satellite was m A. US satellite Explorer-1, orbited in 1958 m B. US satellite Vanguard-1, orbited in 1959 l C. Sputnik-1, launched by the USSR in 1957 m D. US satellite Freedom-1, orbited in 1957 m E. Luna-3, launched by the USSR in The reason that we cannot sent a spacecraft to the Sun's surface is m A. such a mission would take far too much rocket fuel m B. the mission would have to last much longer than a typical spacecraft mission m C. the spacecraft would not be subject to Kepler s laws m D. tidal forces would tear the spacecraft apart as it approached the Sun l E. any possible spacecraft materials would be volatile at the Sun s surface 13. The solar wind is responsible for m A. the Earth's magnetic field m B. dust particles emitted by the solar nuclear furnace m C. increased air circulation that occurs at sunrise each day l D. dragging magnetic fields outward from the Sun m E. Jupiter's energy emission Page 2 of 6

3 14. The most abundant elements in the solar system are m A. carbon and nitrogen m B. nitrogen and oxygen m C. carbon and oxygen l D. hydrogen and helium m E. silicon and oxygen 15. The reason that NASA keeps the Voyager 1 and 2 spacecraft alive is m A. they are targeted at objects in the inner Kuiper Belt, which have not been reached yet m B. they are important to demonstrate the feasibility of the Grand Tour strategy l C. to explore interstellar space m D. they are still giving important data about planets beyond Earth m E. they are listening for possible signals from other terrestrial planets 16. Deuterium is m A. a heavy isotope of helium m B. a manmade element m C. an element that appeared in the hydrosphere during the Pleistocene m D. not found in the Earth's oceans l E. a heavy isotope of hydrogen 17. Interplanetary spacecraft are usually launched from Earth in prograde orbits because m A. that configuration guarantees that they will stay closer to Earth m B. that way they are less likely to be affected by the solar wind m C. that way they can always use a gravitational assist from Jupiter m D. they can take advantage of the Earth s retrograde orbital speed, -30 km/s l E. they can take advantage of the Earth s prograde orbital speed, +30 km/s 18. The Apollo 11 mission to the Moon involved m A. a hyperbolic trajectory from Florida to Tranquility Base m B. rendezvous with a return vehicle already cached on the lunar surface l C. a Hohmann transfer to the Earth-Moon L1 point m D. landing on the lunar farside, since that required less energy m E. a continuous rocket burn from Earth's Roche limit to Moon's Roche limit 19. Iron boils at 3000 K at the Earth s surface. Therefore, iron is m A. a volatile element l B. a refractory element m C. very rare at the Earth s surface m D. very rare in the Sun compared with sulfur m E. very abundant in the Sun compared with hydrogen 20. The source of the Sun's luminosity is m A. decay of tritium isotopes into helium at its center m B. fusion of helium into carbon in its outer layers l C. fusion of protons into helium at its center m D. fusion of silicon into Fe 56 near its center m E. tidal friction from Mercury 21. The temperature of the surface layers of the Sun (the part that we see) is about m A K m B K l C K m D. 500 degrees Fahrenheit m E. 273 K 22. We deduce the chemical composition of the Sun by m A. measuring the velocity of the solar wind m B. returning samples from its surface m C. measuring the apsidal precession rate of Mercury m D. measuring how much energy it emits l E. measuring the depth of dark absorption features in its spectrum 23. The orbit of Earth around the Sun describes a geometric figure called m A. a parabola l B. an ellipse m C. a hyperbola m D. a cycloid m E. a cardioid Page 3 of 6

4 24. Which of the following statements is correct? l A. life is made up of elements that are very abundant in the Sun, such as C, H, O, and N m B. when the solar system first formed, elements out of which life could form were mostly absent m C. despite its apparent lifelessness, the Moon is rich in elements that could form living organisms m D. living organisms are mostly made up of refractory elements m E. all elements beyond H and He were mostly made during the first few seconds of the Big Bang 25. Mercury moves fastest in its orbit at m A. apoapse m B. quadrature with the Earth m C. closest conjunction with Venus l D. periapse m E. the point where it crosses Venus' orbit 26. Liquid water is l A. more refractory than either of its constituent elements m B. more volatile than isopropyl alcohol (C 3H 8O), which boils at 82.5 degrees C at room pressure m C. more volatile than pure oxygen m D. composed of elements which are not seen in the Sun m E. a substance that could never contain deuterium 27. Voyagers 1 and 2 measured the termination shock of the solar wind m A. at 1.3 AU from the Sun m B. at 5.2 AU from the Sun m C. respectively at 11 AU and 12 AU from the Sun m D. respectively at 21 AU and 19 AU from the Sun l E. respectively at 94 AU and 84 AU from the Sun 28. A comet orbits the Sun with an orbital semimajor axis equal to 100 AU. This means that m A. its orbital period is 10 years m B. its aphelion distance is always 200 AU l C. its orbital period is 1000 years m D. its perihelion distance is always 10 AU m E. its orbital period is 100 years 29. The Sun formed from an interstellar cloud l A. 4.5 gigayears ago m B. 4.5 femtoyears ago m C. 4.5 kiloyears ago m D. 4.5 megayears ago m E. 4.5 zettayears ago 30. The plane of the Earth's orbit is called m A. the barycenter m B. the neutrino l C. the ecliptic m D. the equator m E. the tropic of Capricorn 31. If we make the distance between mass M and mass m twice as small, the gravitational force of attraction between these masses m A. becomes 4 times weaker m B. becomes 2 times stronger l C. becomes 4 times stronger m D. remains unchanged m E. becomes 2 times weaker 32. The heavy grey curve in the figure below illustrates Page 4 of 6

5 m A. the fastest orbital path from Earth to Mercury l B. the orbital path from Earth to Mercury that uses the least rocket fuel m C. the L1 and L3 points for Mercury m D. the evolution of Mercury's orbit over 10 9 years due to tidal friction from the Sun m E. the orbital path of comet 1992c 33. The heliosphere is m A. that part of the Earth which is permanently covered with water m B. a special research center near Oracle, Arizona, which demonstrates solar power possibilities m C. a term which is synonymous with the solar corona m D. a region surrounding the Earth which is hazardous to astronauts because of its high energy particles l E. the "bubble'' blown into interstellar gas by the solar wind 34. Aurorae are caused by m A. ejecta of dust from craters l B. impact of high-energy particles on the polar atmosphere m C. plate tectonic processes that only occur on Venus m D. distortion of solar wind magnetic fields by the Moon's core m E. heavy deposition of iron oxides in a planet's atmosphere 35. The human-made objects most distant from Earth are m A. Space Shuttles Challenger and Columbia l B. Pioneers 10 and 11 and Voyagers 1 and 2 m C. Sputnik 1 and Explorer 1 m D. New Horizons and Cassini m E. Phoenix 1 and MERs 1 and 2 FIRST ESSAY QUESTION Write your answers in the spaces provided; use the back of this form if necessary. 36. According to a 2007 news release entitled NASA manned Mars mission details emerge, A 400,000kg (880,000lb) Mars-ship would be assembled in orbit using the Ares V cargo launch vehicle for a 900-day mission to the red planet, according to details that have emerged about NASA's new Constellation program's manned Mars mission. There are some major practical difficulties that will have to be overcome in order to carry out a manned Mars mission. State and discuss two such difficulties, referring to topics discussed in lecture so far: (a) Difficulty #1 - (8 pts.) Transferring 400 metric tons to Mars requires immense energy. Putting just 100 kg (= 0.1 ton) in low Earth orbit takes the equivalent of a car bomb. Therefore, it will be essential to use an energy-efficient orbit to get to Mars, meaning that something close to a Hohmann trajectory will be required. As discussed in class, such an orbit takes nearly a year to get to Mars or to return from Mars, and the launch window requirement means a fairly long sojourn on Mars. There will be no way to avoid a long, 900-day mission, as mentioned in the press release. NASA has never flown a manned mission of anything like this distance and duration, and no one knows whether the human mind and body could stand up over such a prolonged period of zero or very low gravity, together with isolation and remoteness from the rest of humanity. Page 5 of 6

6 (b) Difficulty #2 - (7 pts.) Since the Mars mission has to be of long duration, there is a high probability that the astronauts will be exposed to a high-energy CME event from the Sun. The Apollo astronauts did not encounter such an event because their missions were relatively short. The high level of radiation during a CME is likely to cause serious damage to human tissue and might even lead to death. We do not currently know how to efficiently protect space travelers from this hazard. SECOND ESSAY QUESTION Write your answer in the space provided; use the back of this form if necessary. 37. In late 1957 and early 1958, the USA was in a state of near-panic about its space program. Describe the events that led up to this situation, why they caused concern, and how they influenced the establishment of the civilian space agency NASA. (15 pts.) The October 1957 launch of Sputnik 1 by the Soviet Union was completely unexpected. The Soviet space program was top secret, so secret that even the identity of its Chief Designer, Sergei Korolev, was not revealed. The first reason for great concern on the US side was that the energy required to put a payload in Earth orbit is essentially the same as the energy required to put a weapons payload in a half-orbit and drop it on a target on the other side of the Earth. In other words, Sputnik 1 meant that the Soviets had achieved ICBM capability. The second reason for concern is that the USA had earlier imagined that it was far in the lead in space exploration and had no possible technological competitors. USA national policy at the time was to explore space peacefully through a civilian-controlled space agency. The first launch vehicle to be used for this purpose was the Vanguard rocket, which could only orbit small, compact payloads. Early failures of the Vanguard forced the USA to resort to desperate measures by using the military Jupiter-C rocket to get its first satellite into space. Despite this first departure from policy, since then the USA has continued peaceful space exploration through its civilian agency NASA. [There was an unexpected benefit of having much weaker heavy-launch capability than the Soviets: US engineers were forced to focus on building very small, light electronics packages using semiconductors and integrated circuits. This ultimately revolutionized the consumer electronics industry and all forms of electronics technology.] Page 6 of 6