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If we are searching for life that is at least somewhat similar to life on Earth, the most important criterion in identifying a potentially habitable world is ________.
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Based on current evidence, the elements needed for life are found ________.
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astronomy exam 3
| Question | Answer |
|---|---|
| If we are searching for life that is at least somewhat similar to life on Earth, the most important criterion in identifying a potentially habitable world is ________. | the presence of surface or subsurface liquid water |
| Based on current evidence, the elements needed for life are found ________. | throughout the universe |
| 96% of the mass of living organisms on Earth is made up of just four elements. What are they? | Hydrogen, Carbon, Oxygen, Nitrogen |
| Jupiter is about five times as far from the Sun as Earth. Therefore, the strength of sunlight at Jupiter is about ________ as strong as it is at Earth. | 1/25 |
| How does the strength of sunlight (per unit area) depend on distance from the Sun? | it decreases in proportion to the square of the distance |
| Suppose you were genetically engineering plants that you hoped to grow in a greenhouse on one of Jupiter’s moons. response - correct In this scenario, you would want to engineer these plants to have | larger leaf surfaces, so that they could collect more sunlight. |
| One advantage of water as a liquid medium for life is the fact that it stays liquid over a higher and wider range of temperatures. If we want to find another medium for life that has similar properties, which substance should we pick? | Methanol |
| Which of the following is not an advantage of water over methane, ethane, and ammonia as a potential liquid medium for life? | Water is the only one that melts from solid to liquid form as the temperature increases. |
| What are the three advantages of water that make it seem far more suitable as a liquid medium of life than other liquids? | Water remains liquid over a higher and wider range of temperature. The solid (frozen) form of water is less dense than the liquid form. Water molecules have charge separation (are polar). |
| Media reports sometimes say that there is "water on the Moon." What really has been found is strong evidence for | water ice in polar craters |
| Which of the following explains why Venus is so much hotter than Earth? | Venus's atmosphere contains far more carbon dioxide than Earth's. |
| Is there any place where we might find liquid water on Uranus or Neptune? | Yes, but probably only very deep in their interiors. |
| If you choose a small moon at random from the moons of the jovian planets in our solar system, which of the following are you most likely to find? | Water ice |
| Why do the solar system's many small bodies, such as asteroids, comets, and small moons, seem unlikely as potential homes to life? | They are too cold inside to have liquid water |
| The feature on Mars called __________ is a long, vast network of canyons. | Valles Marineris |
| The __________ vary in size with the martian seasons. | Polar Caps |
| The _________ is a high elevation region dotted with large volcanoes. | Tharsis Buldge |
| The feature called __________ is the largest known mountain in the solar system which is also a volcano. | Olympus Mons |
| The __________ have low elevation and may possibly have once been the location of an ocean. | Northern Plains |
| The __________ are heavily cratered | Southern Highlands |
| Mars has seasons because of its ______, but the southern hemisphere has more extreme seasons because of _____________ . | Axis tilt, Mars' varying distance from the sun. |
| Liquid water is unstable on Mars because of the _________. | Low atmospheric pressure. |
| Which of the following provides the evidence that has allowed scientists to conclude that Mars's southern highlands are geologically older than its northern plains? | The large number of craters in the Southern Highlands |
| Which of the following best explains why scientists conclude that Mars must once have had a much thicker atmosphere and a much stronger greenhouse effect than it does today? | Evidence that liquid water was once stable on Mars. |
| The term “Martians” (as opposed to, say, “Venusians” or “Jupiterians”) became nearly synonymous with alien life because | the idea of a civilization on Mars was popularized by the writings of Percival Lowell and H. G. Wells’s novel The War of the Worlds. |
| In regard to Percival Lowell's claims of a vast canal system on Mars, Alfred Russel Wallace wrote "[a network of canals,] as Mr. Lowell describes, would be the work of a body of madmen rather than of intelligent beings." Why? | The canals claimed by Lowell ran in straight lines for great distances. |
| When we say that liquid water is unstable on Mars today, we mean that ________ | any liquid water on the surface would quickly freeze or evaporate. |
| Why does Mars’s axis swing much more wildly over time than Earth's? | Mars lacks a large moon |
| Models indicate that over hundreds of thousands to millions of years, Mars undergoes large changes in axis tilt. What do we expect to happen when Mars has a larger axis tilt? | Seasons become more extreme, which can enhance the atmosphere and greenhouse effect. |
| Which statement about the martian seasons is not true? Responses | All of Mars has summer at the same time, and half an orbit later all of Mars has winter. |
| The martian “blueberries” are ________. | pebble-sized spheres containing the mineral hematite. |
| Which of the following is NOT a key piece of evidence in favor of past liquid water on Mars? | Orbital photos show a relatively small number of craters on volcanic slopes. |
| Key evidence that Mars may once have had much more water than it does today—perhaps enough to form an ocean—comes from ________ | measurements of the atmospheric ratio of deuterium to ordinary hydrogen. |
| Evidence indicates that Mars’s era of being significantly warmer and wetter ended at least about ________ | 3 billion years ago. |
| According to the leading hypothesis, what happened to most of Mars’s ancient atmospheric gas? | It was stripped away by the solar wind. |
| What must be true if Mars was warmer and wetter in the past? | Mars once had a much thicker atmosphere than it does today. |
| The martian meteorite ALH84001 has structures that look like fossilized bacteria. Why do most scientists doubt that they are actually fossil life? | The structures are too small. |
| Why are robotic landers and rovers sterilized before launch to Mars? | To prevent terrestrial microbes from hitching a ride on the probe and contaminating the Martian surface |
| If life exists on Mars today, it is most likely to be found _____________ | beneath the surface. |
| Why is it considered unlikely that martian microbes could infect Earth organisms after being brought back by a future sample return mission? | Martian microbes are likely to be quite different from terrestrial microbes and, hence, not adapted to infecting Earth life. |
| The process of changing a planet like Mars so that it is more suitable for human colonization is referred to as __________ | terraforming. |
| From the standpoint of the search for life, what is the most significant concern about sending humans to Mars? | The high probability of contamination of the martian surface by microbes associated with human beings |
| Which statement about synchronous rotation is true? | It is a natural consequence of tidal forces acting on a moon. |
| Based on what we know about the terrestrial worlds, why is it surprising to find geological activity on jovian moons? | They are too small. |
| Tidal heating is stronger for Io than for Europa because ________. | Io is closer to Jupiter. |
| If Europa really has an ocean, life that gets energy through photosynthesis is unlikely in this ocean because________. | The icy crust is too thick. |
| What are the observable pieces of evidence that Europa has a subsurface ocean? | Surface features that look like jumbled icebergs, Variations in Europa's magnetic field, Calculations of Europa's internal tidal heating |
| The geological activity of Io and Europa is caused primarily by ________. | tidal forces from Jupiter that heat the interiors |
| Scientists think that Ganymede, like Europa, ______ a subsurface ocean of liquid water because __________________________. | Has, its magnetic field varies with Jupiter’s rotation. |
| How do the possibilities for life on Ganymede and Callisto compare to those on Europa? | Life seems less likely because these moons have less energy available for life. |
| If Europa really does have geysers on its surface, how might the Europa Clipper mission be able to make use of them to learn whether Europa has life? | The spacecraft’s spectrometers could analyze the gas for the presence of organic or biological molecules. |
| Which of the following have we found on Titan? | Abundant organic compounds. |
| Titan shares all of the following geological features with Earth except________. | Volcanoes erupting with molten rock |
| Assuming Enceladus really has a subsurface ocean, which of the following probably contribute to keeping it liquid? | Ammonia acting as an antifreeze, heat form radioactive decay, tidal heating. |
| Why were scientists surprised to find active geology on Enceladus? | Because of its small size. |
| The list of moons in our solar system on which life seems at least potentially possible are: | Europa, Ganymede, Callisto, Triton, Titan, Enceladus. |
| If you have a situation in which there is a chemical disequilibrium, it means that______. | Chemical reactions are likely to occur. |
| The general definition of a redox reaction is a chemical reaction in which ______. | One or more electrons is transferred from an electron donor to an electron acceptor. |
| Chemical disequilibrium is likely to be present in all the following places except ________________. | Icy boulders in the rings of Saturn. |
| What describe the features of what we call "The Habitable Zone" around a star? | It gradually moved outward from a star with time and it is the region around a star in which a suitable sized world could have surface oceans of liquid water. |
| What would happen to Earth if we could somehow move it to Venus's orbit? | It would suffer a runaway greenhouse effect that would presumably kill off life on our planet. |
| Which of the following statements about Venus and the habitable zone is correct? | Venus is not in the Sun's habitable zone today, but might have been in the distant past. |
| What best describes current thinking of Mars and the Sun's habitable zone? | Mars might be in the Sun's habitable zone today, in which case it might be habitable if it were larger in size. |
| Is Europa in the Sun's habitable zone? | No! |
| If we want to restore the climate to a state more like it was before humans started to cause global warming, we need to _______. | Stop using fossil fuels, convert out energy to use renewable energy only, find a way to remove carbon dioxide from the atmoshpere. |
| Key evidence that Venus once had much more water than it does today comes from _____. | Venus's relatively high ration of deuterium to ordinary hydrogen atoms |
| In terms of the gases outgasses by volcanoes, Venus's atmosphere today seems to have _______. | too little water vapor. |
| A key piece of the runaway greenhouse effect is that fact that warm air holds _____ water vapor. This ____ the greenhouse effect. | More, strengthens. |
| Known on Earth, what is the only natural source of phosphine? | Life |
| Based on all current evidence, if Venus had been born at Earth's distance from the Sun, the Venus today would probably ______. | have oceans and an atmosphere much like Earth. |
| The reason that some scientists think that Venus might have had oceans early in its history is that ____. | The sun was probably dimmer at that time. |
| What will happen to the Sun's habitable zone in the future? | It will move outward. |
| Which of the following is most likely to render out planet Earth no longer habitable in the future? | A runaway greenhouse effect, between about 1 to 3 billion years from now. |
| Warmer temperatures allow water vapor to reach higher altitudes. As a result, water vapor is dissociated by UV light and lost to space. | Moist greenhouse effect |
| Higher temperature increases evaporation and warmer air holds more water vapor. As a result the green house effect is strengthened and the planet warms more. | Runaway greenhouse effect |
| Atmospheric carbon dioxide condenses into snowflakes and falls to the surface. As a result, the atmosphere thins and the greenhouse effect weakens. | Cold atmosphere |
| Beyond this distance, no greenhouse effect can warm the planet enough to keep it from freezing. | Thick atmosphere, strong greenhouse effect |
| Why is having a substantial atmosphere thought to be a requirement for surface oceans? | Water would be unstable without enough atmospheric pressure. |
| Global warming refers to _____. | an increase in Earth's average surface temperature. |
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avxleigh