Astrobiology (Please watch the video, each question should be answered by about

Question

Astrobiology (Please watch the video, each question should be answered by about 8 to 10 (depending on length) meaningful sentences of response.

Comparing Worlds: Climate Catastrophes in the Solar System Part 2

Dr. David Grinspoon (Denver Museum of Nature and Science)

(3) Summarize the basics of the climate catastrophe that previously occurred on Venus based on information provided in the video.

(4) Describe a previous climate catastrophe other than the K/T event, including some relevant biological ramifications. (Include refs.)

Explanation / Answer

3. Venus is similar to earth in many ways. It has a similar size, mass, composition and nearer to earth than any other planet in the solar system. But still the atmosphere and extreme temperature of Venus is quite different from the earth. Since Venus is near to the sun as compared with the earth it received much sunlight. Due to this its ocean water evaporated. The water molecules present on the Venus surface were broken by the ultraviolet radiation and the hydrogen gas escaped to space. As as result the CO2 builds up in the atmosphere called as runaway greenhouse effect which gives rise to the present conditions of Venus. Because of its thick atmosphere containing CO2 it traps the heat.

The Venus had earlier habitable temperatures and had significant water in the form of ocean. But now due to the greenhouse effect its conditions are completely different now. The surface temperature of Venus is now 864 Fahrenheit and there is almost no water vapour. It has a thick atmosphere of CO2, 90 times as thick as of earth and the conditions on the Venus are now hostile to the life.

4. There is mass extinction event at the Permian Triassic boundary popularly known as P-T extinction. In this extinction about 96 % of marine species and 70% terrestrial species vanished. There are various theories proposed of this extinction like asteriod impact, volcanism, greenhouse effect, explosion of methane. During this temperature of sea water has increased at the beginning of Triassic so that marine organisms were not able to survive this temperature and died. Also during this period there was significant changes in the stable ratios of carbon.

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