Search for Life in the Universe

: Search for Life in the Universe
Use the plot on the backside for your answer to question 2. Write all other answers on separate sheets of paper and staple them together. (Remember where you can find a stapler?!)
The Labeled Release (LR) experiment on Viking 1 and 2 was the only one that resulted in a positive response. The latest account of those findings has been recently been published by
Levin, G. V., & Straat, P. A.: 2016, “The Case for Extant Life on Mars and Its Possible
Detection by the Viking Labeled Release Experiment,” Astrobiol. 16, 798–810
see http://lcd-www.colorado.edu/~axbr9098/teach/ASTR_2040/material/ for a local copy of Levin+Straat16.pdf (and other potentially interesting papers). Work with the 2016 paper (i.e., read mainly what you need) to answer the following questions.
(i) What kind of compounds did the nutrient solution consist of?
(ii) Using their Figure 2, what are the approximate count rates per minute of any released 14Cbased gases for Viking Lander 1 after about 5 hours and after about 24 hours?
(iii) Using their Figure 3, what was the approximate count rate for their California “Aiken” soil sample under terrestrial conditions after about 5 hours and under Martian conditions after about 24 hours?
(iv) Later in the mission, a modified control was introduced for Viking Lander 2. Why did they do this and what was the result? Why was this modification thought to be particularly suitable for Mars compared to Earth?
(v) On Viking Lander 2, during cycle 5, an improvised experiment was conducted on a soil sample that had previously being tested. For how long and at what temperature had this sample been stored and what was the result?
(vi) Why is a biological explanation difficult to accept? [Hint: which other Viking experiment yielded results incompatible with life?] (vii) Which nonbiological explanations have been put forward? What are the problems with these explanations?
2. We have known for some time that Mars’ surface pressure is generally too low to support liquidwater, but this is only true most of the time. Using the phase diagram of water (next page), answer the following questions to see how close Mars is to supporting liquid water on its surface.
(i) Mars’ surface air pressure at Terra Sirenum (see Google Mars for details!) is typically 5 mbar and has a temperature of about 220K. Mark these surface conditions on the plot with a point. What phase would you expect water on Mars to be from this information?
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(ii) Assuming that the air pressure could be held constant, would it be possible to raise Mars’ surface temperature to the point where liquid water could exist?
(iii) At Hellas Planitia, the floor of the Hellas Impact Basin, surface pressures soar to 11 mbar. Assuming the same 220K surface temperature, please mark the surface conditions of Hellas Planitia on the phase diagram. What phase of water would you expect to exist here?
(iv) Suppose we recalculate our values for Mars’ southern summer – when the planet is physically closer to the Sun. Let’s suppose the increased sunlight raises the temperature by 20%, and let’s ignore changes in pressure, draw your two temperatures using this larger temperature. Do either of your previous locations potentially allow for liquid water?
3. Valles Marineris. The Grand Canyon in Arizona is a river carved trench over 400km long, almost 2km deep and 30km wide. Valles Marineris, a rift valley on Mars, is over 4000km long with a depth of over 6km and 200km wide.
(i) How many times larger is Valles Marineris than Grand Canyon in terms of length, depth, and width?
(ii) The Amazon River, discharges 200,000m3/s (three hundred times more than our Colorado River!). How long would it take the Amazon River to fill Grand Canyon to the brim?
(iii) Given that you know from the first part how much larger Valles Marineris is, how much longer would it take for the Amazon River to fill up Valles Marineris?