HW #2 Question #5

     Scientists have observed what they believe to be ancient riverbed on mars from an area known as Arabia Terra. They used new information from NASA's Mar's Reconnaissance Orbiter to find said information. The MRO has a resolution of 6 meters per pixel as opposed to the last mission that had 100 meters per pixel.

     Throughout history as people have looked at other celestial bodies they have thought to have found places where there may be water. Like the man we learned about in class that saw channels of water on the moon. As technology increases, however, these observations are much more credible. Still the only way to definitively prove whether there was water in Arabia Terra or not is to send a mission to the planets surface to analyze, such a plan is in the works now.

http://www.astrobio.net/also-in-news/fossilised-rivers-suggest-warm-wet-ancient-mars/

http://mars.nasa.gov/mro/news/whatsnew/

HW 2: #3 Arsenic-life Bacterium

“‘Arsenic-life’ bacterium prefers phosphorus after all”, written by Daniel Cressey, discussed the debunking of a previous article posted in 2010. The article, “A Bacterium That Can Grow by Using Arsenic Instead of Phosphorus”, written by Felisa Wolfe-Simon & others, claimed that one of the bacteria in Mono Lake in California, which is very high in arsenic, could metabolize without phosphate and instead use arsenate. After several subsequent articles, this theory was proven to be false, and organisms need phosphate to grow. Specifically, an article published in October of 2012, “The molecular basis of phosphate discrimination in arsenate-rich environments” by Mikael Elias & others, tested to see how these bacteria even differentiate between the two extremely similar molecules. Being from the same group on the periodic table, phosphorous and arsenic have practically identical electronegativities and Van der Waals radii.

This was the foundation for Wolfe-Simon’s article, but much of their results and findings were viewed subjectively because they wanted the outcome to be true. In the research done by Elias and his colleagues, they discovered that not only could these bacterial proteins differentiate between phosphate and arsenate, they did so through one key chemical bond. They all showed an extreme preference for phosphate, particularly the one bacterium that began this controversy which filtered in phosphate at levels of 4,500-fold the level of arsenate to phosphate. Arsenate was clearly still needed for these bacteria due to the lengths they went to in order to bond with all of the phosphates they could. However, some of the bacteria were able to bond with the arsenate after depleting the supply of phosphate, though the hydrogen bond was much weaker when the bacterium bonded with arsenate.

a. P. fluorescens PBP bound to phosphate has a more direct connection

b. P. fluorescens PBP bound to arsenate has an angled connection

Knowing that bonds could occur with arsenate when given no other option opens the door to the possibility that there may be life on other planets that survive without phosphate, or in fact use arsenate preferentially over phosphate. It would be interesting to test these, and other bacteria, in a pure arsenate solution, removing their ability to choose phosphate over arsenate.

Sources:

‘Arsenic-life’ bacterium prefers phosphorus after all: http://www.nature.com/news/arsenic-life-bacterium-prefers-phosphorus-after-all-1.11520

The molecular basis of phosphate discrimination in arsenate-rich environments: http://www.nature.com/nature/journal/v491/n7422/full/nature11517.html#supplementary-information

A Bacterium That Can Grow by Using Arsenic Instead of Phosphorus: http://science.sciencemag.org/content/332/6034/1163.full

http://chemical-elements.findthedata.com/compare/6-69/Arsenic-vs-Phosphorus

Homework #2 ---- Question #4

As of this year paleontologists have discovered the oldest known fossil known to our earth. It was an isua stromatolite that was determined to be 3.7 billion years old. At that point in time the oldest known fossil was 220 million years old. The stromatolite was found on the edge of Greenland’s icecap. Outside of the excitement of the discovery of a living fossil well before one was known, there were other implications that one can extrapolate about prehistoric life. We have common theories of the nature of the earth 3.7 billion years ago. Because we have an understanding of these conditions, these newly found fossils broaden the scope of the complexities of life, and the environments that life can be harvested in. The conditions Earth was in when the fossils were dated have similarities to the environment we know Mars has had in the past. Because of these parallel similarities we can better understand if and when mars could have inhabited living cells. Not only was the stromatolite alive during Mars like conditions, but was different than discovered prehistoric life, in that it was more than a single celled organism, but were communities of microbes in complex ecosystems. This understanding illuminates more understanding to the possibility of life on Mars or other planets.

Stromatolite fossil found in Greenland

Taking this information, we can conduct studies and experiments in order to further understand life in on our planet and the possibility of it off our planet. To further understand the nature in which life lives in harsh climates, we could take stromatolite found on earth or organisms that are similar, and place them in extreme environments mimicking those of other planets or moons and observe the impact it has on life. Doing this could broaden the understanding of how life could have or does survive in different kinds of environments in our universe.

Stromatolite 

Reference:

http://astrobiology.com/2016/09/scientists-discover-37-billion-year-old-fossils.html

HW 1

1.) Finding life on other planets would give scientists a different perspective on how our world fits in our universe and we can learn more about life on earth by comparison to this new life.
6.) The laws of physics are applied universally throughout the universe as we observe them, so is our understanding of chemistry. It is most likely that alien life will be composed of carbon like us, due to the plentiful amount of carbon in our universe.
11.) b
16.) a

HW CH1 AST 112

AST CH1 Questions

2. For one thing, we can actually see other planets and moons that could be habitable, whereas in the past we could not even see them. Secondly, we have a better understanding of life, and what conditions must be in place to harvest life. Because we know conditions for life and we can observe more and more planets with these potential conditions, we can actually reasonably say life outside of Earth is possible.

7.

1.       Mars because we can observe evidence of dried up water canals that could have harvested life in the past. Also there are significant amounts of water ice currently.

2.       Europa because it has deep oceans of liquid water under icy crust.

3.       Ganymede and Callisto because they show evidence of subsurface oceans.

4.       Titan because it has a thick atmosphere and lakes of liquid methane.

12. C

17. C

Homework 1

3. geocentric universe refers to the belief to that the Earth is the center of the universe. A geocentric view resulted in a limited knowledge of our universe, but when it became widely accepted that the sun was the center of our solar system, the scientific community made leaps and bounds towards the understanding of the universe we have now. Now we know that we're but one solar system, among countless others.

8. Currently, it would take far to long to send a spacecraft to other stars to really make it a feasible option for detecting life on other planets. We can however, use current telescope technology to detect extrasolar planets, and as technology advances, we may be able to receive better images to look for and understand visual signs of possible life.

13. (a) the ancient idea that Earth resided at the center of the universe.
Geocentric, geo meaning Earth & centric meaning centered, describes an Earth centered view of the universe.

18. (c) evidence suggests that Mars had liquid water on its surface in the distant past.
Water is one of the basic necessities for life (as we know it), but it is important that it's liquid water. Liquid water is needed for life (as we know it), so a planet like Mars must have the proper conditions to facilitate liquid water.