Comins DEU 3e Ch 05 Quiz 3 completed The correct answers are written in bold, italic and underlined. The most important questions to study for the exam are highlighted. 1. Which of the following descriptions best characterizes the surface of Mars? • More-or-less uniform surface of lightly rolling hills and few craters, with two large, continent-sized areas raised above the average terrain • Two distinct hemispheres: large, lightly cratered asteroid impact basins in the eastern hemisphere and dense cratering with only two small asteroid impact basins in the western hemisphere • Two distinct hemispheres: volcanoes and volcanic plains in the northern hemisphere and extensive impact cratering in the southern hemisphere 2. What evidence is there for the proposal that at least parts of the Martian surface are very old? • The observation of polar icecaps on Mars, which probably formed from outgassing water as Mars was being formed, at least 4 billion years ago • The observations of abundant craters in the southern hemisphere, which are so numerous that they must date back at least 3 billion years • The observation of giant volcanoes that, at the estimated rate of lava flow, would have needed at least 2 to 3 billion years to grow to their present size 3. Which of the following statements best describes the magnetic field of Mars? • A large global magnetic field that repels the solar wind, much like the magnetic fields of the Earth and Mercury • Local magnetic fields over some parts of the planet, but no global field of the kind that the Earth and Mercury have • None, or at least too weak to be detected by current technology 4. On which planet can dust storms occur that are so extensive that they can sometimes hide all surface features from view? • Mars • Venus • Mercury 5. One major feature of the Martian "climate" is • totally overcast conditions, with thick sulfuric acid clouds. • massive and intense thunderstorms, with intense lightning. • huge dust storms. 6. The appearance of the sky on Mars is often pink, red, and brown, in distinct contrast to the Earth's blue sky. The physical reason for these colors is • carbon dioxide in the atmosphere, which absorbs blue light and scatters red light from the Sun. • methane in the Martian atmosphere, which is a powerful absorber of the blue and green parts of the solar spectrum and allows only red light to reach the Martian surface. • fine iron oxide dust blown into the atmosphere by wind storms. 7. The length of each of the Martian seasons, compared to those on the Earth, is • about half as long as the Earth because both the Martian period of revolution and synodic period are twice as long as those of the Earth. • about twice as long because of Mars' orbital period. • about the same as the Earth since the tilt of Mars' spin axis and rotation rate are similar to those of the Earth. 8. Which of the following planets or planet-sized objects is most strongly suspected of having abundant water at the present time? • Our Moon, one piece of evidence being ancient flow channels on its surface • Venus, one piece of evidence being its global cloud cover • Mars, one piece of evidence being water-soaked clay in certain meteorites on the Earth 9. On the question of the existence of water on the planet Mars, present evidence indicates that • there has been significant water flow in the past, some water ice exists at the poles at present, and water may exist now as permafrost under the Martian surface. • there is liquid water on the planet surface that flows along flood channels and canals during the summer months, the dampness producing changes in the color and shading of the planet that are seen through telescopes on Earth. • there is not and probably never has been water on Mars. It is an arid, dusty, and dry planet where any water present at the planet's formation would have rapidly evaporated or combined with iron to form iron oxides (rust). 10. Evidence for water stored as permafrost under the Martian surface is shown in • haze layers and steam vents seen by orbiting spacecraft near active volcanoes on Mars. • the darker color of some parts of the surface of Mars. • river valleys extending away from obvious impact craters. 11. The average surface conditions near Mars' north and south poles can best be described as • hot, dry, and desert-like. • cold, rocky, and very dusty. • cold and icy. 12. The /Pathfinder/ spacecraft and its robotic rover, /Sojourner/, landed in what was believed to be an ancient flood-plain on Mars. Which of the following pieces of evidence did these spacecraft NOT find to indicate that water had indeed flowed over the landing site? • Ice in sheltered depressions below the larger rocks • Rocks that had once been aligned by flowing water • Rounded rocks showing evidence of having been eroded by flowing water 13. Deposits of salt have been found in a 1.2-billion-year-old Martian meteorite. What is believed to be the source of this salt? • Contamination from the soil on the Earth after the meteorite landed • The drying up of an early Martian ocean • Chemical reactions in melted permafrost in volcanically active areas 14. The Mars rover, /Opportunity//,/ discovered abundant small, dark spheres of hematite (whimsically called "blueberries" by project scientists) embedded in rocks around the landing site. What is believed to be significant about these "blueberries"? • They suggest that this part of Mars was under water at some time in the past. • They provide evidence that Mars was struck by a large, iron-rich planetesimal in its early history, prior to the formation of the rocks. • They show that these rocks formed under desert-like conditions, indicating a dry past for Mars. 15. The results of the /Viking/ experiments to detect life on Mars were • evidence of chemical reactions, some of which mimicked biological activity. • no response, indicating an inert surface composition. • evidence of abundant biological activity. 16. The biological experiments on the /Viking/ landers that explored the Martian surface measured intense chemical activity when soil was moistened with water. These reactions have been interpreted as non-biological chemical processes mainly due to • the reaction of water to the sulfuric acid that pervades the planet's surface. • unstable but very reactive chemical compounds containing loosely bound oxygen atoms reacting strongly with the water. • the release of CO2 from the rocks in a manner similar to the release of CO2 from a fizzy soft drink. 17. What would an observer on Mars watching the Martian moon Phobos see that is fundamentally different from what we see on the Earth when looking at our Moon? • Phobos revolves around Mars at the same rate that Mars rotates, remaining stationary above one point on the planet's surface all the time. • Phobos rises in the west and moves rapidly across the Martian sky, setting in the east in about 5 or 6 hours. • Phobos rotates to show all parts of its surface to an observer on Mars during its orbital motion (nonsynchronous motion). 18. The two moons of Mars, Phobos and Deimos, are • irregular in shape, about as big as the major moons of Jupiter, but with very dark surfaces; hence, they cannot be seen easily from the Earth. • spherical, one about the same size as our Moon and the other about half the size of our Moon. • small and irregular in shape. 19. What is believed to be the origin of the two moons of Mars, Phobos and Deimos? • They condensed from debris thrown out by a gigantic collision between a large planetesimal and Mars early in Mars' history. • They formed in orbit around Mars during the formation of the solar system, when Mars was accreting from the solar nebula. • They are asteroids that were gravitationally captured into orbit around Mars. 20. The mass of Jupiter is determined by • using Newton's laws on the observed motions of Jupiter's moons. • applying Kepler's laws to the measured motion of Jupiter in its orbit around the Sun. • calculating its volume from the observed diameter and multiplying this by its average density.