Jakes Exam 2 Essay Questions Flashcards
Select a source of energy that is not known to be utilized by any form of life on earth. Describe the energy that could possibly be used and how it would work. In addition, if the potential source of energy that you selected has any deleterious effects, describe the protections life forms would possess to protect themselves while using this source of energy.
One possible source of energy alien to life on earth would be electromagnetic waves other than visible light, such as UV light. On earth photosynthetic organisms use visible light, but that may be simply because that light is most prevalent. On other worlds with a different classification of star, they might absorb shifted wavelengths of light compared to ours. An issue would be organisms that absorb UV radiation is the damaging effects this wavelength has on proteins and DNA. As we know UV radiation is very dangerous to life, so there would be a need for very different biochemistry than we know of.
Carbon can be considered a “Goldilocks-type” of element for life. Name and describe at least three characteristics of carbon that makes it ideal for “life as we know it”.
Carbon allows for the formation of 4 covalent bonds, which allows it to make complicated molecules with strong attachments. It’s also relatively small, unlike silicon, which allows it to have double bonds and more stable structures. Also, it is soluble in water and very abundant. This allows for a higher chance of interacting with other molecules in a meaningful way.
The article, “Chance and Necessity in Biochemistry: Implications for the Search for Extraterrestrial Biomarkers in Earth-like Environments” written by Davila and McKay, explores how there can be life based on carbon but not on the same biochemistry that we are familiar with on Earth. Explain how this can be.
Biochemistry is the sum of necessity and chance. While a common chemistry at the origin of life (and the laws of thermodynamics) necessitates some similarities among living organisms, certain biochemical traits may differ depending on relative abundance of complex molecules. In essence, the authors explained the biochemistry of life as a “LEGO set” - we all share some pieces, but the unshared pieces represent what is uniquely available in each environment. The best example of this are the amino acids - the simple ones are likely common in our universe while the more complex ones may differ.
One of the critical environmental parameters for life to occur is that there must be a liquid solvent present. Describe the reasons why life needs a liquid solvent.
While we cannot state for certain that life cannot form without a solvent, there are certain things that a solvent provides that make them extraordinarily beneficial for the formation of life. Firstly, a solvent provides an environment that reinforces the stability of certain chemical bonds while allowing other chemical bonds the ability to change their molecular state. A solvent also has the ability to dissolve certain molecules but not others, providing boundaries and surfaces for interactions. A solvent also is able to maintain sufficient concentrations of reactants. Finally, a solvent can maintain limits to temperature and pressure, and serve as a buffer against environmental fluctuations.
In the hypothesis paper of Limaye et al., “Venus’ Spectral Signatures and the Potential for Life in the Clouds”, the authors present the case that life could occur in the clouds and possess metabolisms based on the use of iron and sulfur. Discuss their justifications for these ideas.
The lower cloud layer of Venus contains moderate temperatures and pressures sufficient for life. UV spectrum analysis has led to the strong belief that this atmosphere contains sulfuric acid droplets and ferric chloride. This is what prompted the question of whether or not biology could exist in this atmosphere with an iron or sulfur centered metabolism. The best justification for these metabolisms are organisms that already exist on earth, in particular one that thrives at low pH and obtains energy from the oxidation of ferrous iron, and one that oxidizes elemental sulfur and utilizes ferrous iron as a terminal electron acceptor.
How might you recognize evidence of past habitability on Mars?
We could look for geological evidence, such as erosion, fossils, or formations. We also notice signs that early Mars was similar to early Earth, like signs of water (frozen water, formations from lakes, lava tubes). The atmosphere on Mars is an important thing to consider as well, we know from magnetized rocks that Mars once had a magnetic field, which meant it likely had a much stronger atmosphere than it has today.
What clues of biosignatures might you look for?
Fluid inclusions on salt minerals on mars might contain microorganisms. There are also hematite concretions called blueberries that might contain microorganisms. The presence of metabolic byproducts is a classic thing to look for. The atmosphere might also contain past byproducts of life.
Do you think it will be easy to decide which rocks to sample for return to Earth?
No, multiple areas may be promising for different reasons. We can only return 30 samples, and there are arguments on which areas to chose. Ex: Should we choose an area that looked like it might have contained water, or should we choose an area with salt minerals that might contain fluid inclusions?
