PHYS 3510 Lecture 4: 4.1Life_notes

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greymacaw639

21 Feb 2016

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If we want to search for life, we must understand what life is. Note: should distinguish between response to environment (which an individual can do during its life) and adaption (which happens to species over many lifetimes). Important that we understand evolution both as human beings and in terms of having a general understanding of how live has changed over time and become so complex. Centres on charles darwin but it was just developed and finalized by him. Lots of work on this has been done over time and more recent genetic research has given us a better understanding of this. Although there are many different types of organisms, all shapes and sizes, they are all formed from cells. Cell membrane: keeps the good stuff in and the bad stuff out. We have talked about distance scales in astronomy. Horizontal scale: nanometers in powers of 10. In biology, we need to think about much smaller scales.

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13.44 ... CP Exploring Europa. There is strong evidence that Europa, a satellite of Jupiter, has a liquid ocean beneath its icy surface. Many scientists think we should land a vehicle there to search for life. Before launching it, we would want to test such a lander under the gravity conditions at the surface of Europa. One way to do this is to put the lander at the end of a rotating arm in an orbiting earth satellite. If the arm is 4.25 m long and pivots about one end, at what angular speed (in rpm) should it spin so that the acceleration of the lander is the same as the acceleration due to gravity at the surface of Europa? The mass of Europa is 4.80 X 1022 kg and its diameter is 3120 km.

How many ¹⁴C nuclei decay per second ina 70kgperson, assuming that the person's body contains 12% of carbonandthat there is one ¹⁴C nucleus forevery10¹²¹⁴C nuclei?

How much time must pass after this person dies beforethe¹⁴C activity decreases to one decay per second?

(Note we need to get a value of the half-life of¹⁴Cfrom an outside source)

2.27. BIO Are We Martians? It has been suggested, and not facetiously, that life might have originated on Mars and been car- ried to the earth when a meteor hit Mars and blasted pieces of rock (perhaps containing primitive life) free of the Martian sur- face. Astronomers know that many Martian rocks have come to the earth this way. (For instance, search the Internet for "ALH 84001.") One objection to this idea is that microbes would have had to undergo an enormous lethal acceleration during the impact Let us investigate how large such an acceleration might be. To escape Mars, rock fragments would have to reach its escape velocity of 5.0 km/s, and that would most likely happen over a distance of about 4.0 m during the meteor impact. (a) What would be the acceleration in m/s and g's) of such a rock frag- ment, if the acceleration is constant? (b) How long would this acceleration last? (c) In tests, scientists have found that over 40% of Bacillus subtilis bacteria survived after an acceleration of 450,000g. In light of your answer to part (a), can we rule out the hypothesis that life might have been blasted from Mars to the earth?

PHYS 3510 Lecture 4: 4.1Life_notes

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