30.3.0 Searching for Life Beyond Earth

22. Photosynthesis, once it was planet-wide, changed the atmosphere of the Earth by introducing a significant amount of a. oxygen b. carbon dioxide c. methane d. ammonia e. vibranium

a. oxygen

19. Which of the following is, to the best of our knowledge, in the habitable zone of its star: a. a "hot Jupiter" taking 4 days to orbit a G-type main sequence star b. a planet about 1.05 AU from a G-type main sequence star c. a Jupiter-mass planet taking 15 years to orbit a K-type main sequence star d. a planet in an orbit the size of the Earth's around a red giant star e. all of the above

b. a planet about 1.05 AU from a G-type main sequence star

23. Which of the following is a biomarker that could be used from an observatory around a nearby star, with the right equipment, to identify the Earth as a planet with life: a. the presence of a large moon around the Earth b. free oxygen in the Earth's atmosphere c. the abundance of micro-organisms in the deserts of the Earth d. the fact that most of our atmosphere is made of nitrogen e. ice in the Earth's polar caps

b. free oxygen in the Earth's atmosphere

20. Astronomers have discovered a planet orbiting Proxima Centauri, the star closest to the Sun. This is a star of spectral type M, with 12% the mass of the Sun and 15% the size of the Sun. The habitable zone around this star would be a. much larger (wider) than the Sun's b. much closer to the star than the Sun's c. in about the same place as the Sun's asteroid belt d. much more narrow (small) than the diameter of any planet e. the source of all the UFO's that have been reported by UFO believers on Earth

b. much closer to the star than the Sun's

15. One place that astronomers think might have had life start long ago is Mars. Which of the following is not a discovery that we have made on Mars so far? a. observing what looks like dried up river channels from orbiting spacecraft b. the discovery of organic materials (the chemical building blocks of life, such as amino acids) by spacecraft that have landed c. the discovery that Mars long ago had plenty of flowing water, from the composition and layering of some of the rocks examined by Mars rovers d. the discovery of mudstone on Mars, which indicates that ancient Mars may have been more habitable than Mars today e. the discovery of significant amounts of frozen water on Mars, under the surface

b. the discovery of organic materials (the chemical building blocks of life, such as amino acids) by spacecraft that have landed

21. What makes the Earth different from the other worlds that might have life in the solar system (and easier to detect from far away) is that only Earth a. has liquid water on it; no other world in our solar system has water b. has temperatures in some places where chemical change is possible c. has a solid surface d. has a biosphere on its surface where photosynthesis can take place e. has the chemical ingredients from which life might begin

d. has a biosphere on its surface where photosynthesis can take place

16. According to astronomers, which of the following places in the outer parts of our solar system might be a reasonable place for life to exist? a. in the core of the planet Saturn b. in the rings of Neptune c. in the mountains of Pluto d. under the ice of Jupiter's moon Europa e. on the surface of some of the smaller members of the Kuiper Belt

d. under the ice of Jupiter's moon Europa

17. What discovery about Saturn's moon Enceladus has encouraged astronomers to think of that moon as a possible place where life might exist? a. Enceladus has a strong magnetic field b. Enceladus has rivers of liquid water flowing on its surface c. There are radio signals coming from Enceladus which indicate they might be made by intelligent life d. Enceladus has a thick atmosphere with a significant amount of oxygen e. There are plumes of salty vapor coming from cracks in Enceladus' surface

e. There are plumes of salty vapor coming from cracks in Enceladus' surface

18. One reason that some scientists think that there may be life under the icecrust of Jupiter's moon Europa is that: a. Europa is unusually warm on its surface; in some places the climate resembles Hawaii on Earth. b. Life has already been found on Io, Jupiter's inner-most large moon c. Life has been found on Earth, at the bottom of the ocean, deriving its energy not from sun-light but from hot mineral-laden vents coming from deeper inside our planet; something similar could happen at the bottom of the ocean on Europa d. meteorites blasted off Europa have been found on Earth and we detect the building blocks of life inside these meteorites from Europa e. we are receiving intriguing radio messages from Europa that indicate some form of intelligence lives there

c. Life has been found on Earth, at the bottom of the ocean, deriving its energy not from sun-light but from hot mineral-laden vents coming from deeper inside our planet; something similar could happen at the bottom of the ocean on Europa