So I recently became interested in the greatest explorations of all time because I was wondering if one could glean what particular elements were present during each one that made them especially great. So I set about making a list - and I've got some discussion about this which I'll post later.
My criteria was mainly one thing - How did the exploration in question affect the everyday lives of people of the world?
Since I'm not a historian I may have missed on a few of these, I also owe much to friends and coworkers who helped provide suggestions and arguments. Here is the list:
Tier 1 – Greatest Explorations
Apollo 11
Cultural and historical impact is huge and worldwide.
Christopher Columbus
The historical and cultural impact of this voyage is indisputable
Hubble Space Telescope
This borders on a different category, but did travel to orbit. Our first real step into understanding our universe.
Voyager Spacecraft
My personal #1, the pictures returned from these spacecraft continue to inspire and set the stage for exploration of the solar system. Pioneer should be lumped in here as well I think.
Alexander the Great
Reshaped Europe and Asia, both through conquest and scientific/cultural exchange.
Darwin
The most influential expedition in our understanding of where we came from. Although this also borders on a strictly scientific discovery (which is a different kind of exploration), but he did go somewhere relatively unexplored.
Odysseus
Whether or not he really existed and did what he claimed, the account of his travels is part of the foundation of western culture and represents the quintessential exploration.
Tier 2 – Great Explorations
Marco Polo
Credited with bridging east and west. Perhaps most famous because of the book written about his travels by an author after he returned.
Ibn Battuta
The Arab Marco Polo. Lived in the 14th century and travelled from Morocco all the way to China and back again. Also wrote extensively about his life.
Apollo 15
Possibly the most important scientific mission of the Apollo era. Also brought in the “grandeur”.
Viking
First visit to Mars which had captivated imaginations for decades. Probably ranked here because I’m biased.
Speke-Burton
Discovered the source of the Nile – a major discovery for the era. Also represents the Victorian exploration of Africa which had a huge impact on the culture at the time.
Ferdinand Magellan
First circumnavigation of the globe, although a Pyrrhic victory. Discovered the Magellan strait, and also discovered the international date line because their ship log suggested it was a day later than it really was after they returned.
Lewis and Clark
Probably put this here because we live in the US. Anyhow, a seminal exploration of the American west – also represents many others that came afterwards.
Napoleon in Egypt
He brought along scientists and photographers and rediscovered ancient Egypt in Europe. This ignited a cultural phenomenon.
Tier 3 – Human Achievement
(However usually didn’t result in substantial cultural change or scientific discovery)
Amundsen
First to reach south pole. Widely heralded and an incredible testament to pure exploration. Also Amundsen discovered the NW passage – a big feat for its time.
Yuri Gagarin
First to orbit the Earth – if I lived in Russia this would replace Apollo 11. Not sure how to weight these, but I don’t think both deserve to be in the top tier. I think the returned samples from Apollo 11 and science from them put it at the top.
Captain Cook
A seminal figure in global exploration
Edmund Hillary-Norgay
Incredible achievement even though Everest isn’t really the highest mountain…
Apollo 13
Incredible statement on the power of human endurance and innovation.
Sir Francis Drake
Pirate, Explorer, Hero. Was the first Englishman to circumnavigate the Globe.
Xenophon & the 10 thousand
This is from a famous account of a greek mercenary contingent stranded deep within the Persian empire and having to fight its way back home. Also primarily famous because of the written account.
Heyerdahl
Famous book, and an incredible journey that represents the real explorers who first crossed the pacific.
Shackleton
Incredible story – probably more famous because of the photos and accounts that survive.
Lindberg
Another classic accomplishment – 33 hours straight!
Leif Ericson
First western settlement of the North American continent – historical significance was perhaps foiled by global cooling?
Chinese Exploration – Admiral Zheng He
According to Wendell, if these expeditions hadn’t stopped, there may have been a Chinese armada at England in the 15th Century.
Tier 4 – Honorable Mentions
Ballard - Titanic
Jules Verne
Galileo to Jupiter
Magellan to Venus
Cassini to Saturn
Cortes – Mexico/Central America
Peary – First to the North Pole
Post – First to fly around the world
Challenger Expeditions – First dedicated naval expeditions to explore the oceans
John Wesley Powell
Stanley-Livingston
LaSalle
Mississippi River
Prince Henry the Navigator
Portuguese Explorer
Jacques Cousteau
Wednesday, March 30, 2011
Problems in Mars Science - Mysteries or Puzzles?
I recently came across an article written by Malcolm Gladwell in the New Yorker called "Open Secrets". This seems to be about the fall of Enron and the prosecution of Jeffrey Skilling, but it also discusses an interesting way of thinking about problems. The article sets forth a dichotomy - a problem can be viewed as a puzzle or a mystery. These terms are a bit counter-intuitive and describe concepts that don't quite jive with what you might think those words mean.
So let me define the terms here. In the article a puzzle is a problem which has a definite solution where new information will yield an obvious answer. A mystery is a problem where we may in fact have too much information and may not come to a satisfactory conclusion. Gladwell argues that it is critical that we identify the particular type of problem we face (puzzle vs. mystery) because if we approach a mystery like a puzzle we will utterly fail to address it adequately.
If I may, I'll offer this analogy to make this clearer. Suppose you have a 1000 piece puzzle but are missing 900 of the pieces. You can approach this problem in two different ways - One person may decide to go looking for the missing pieces - maybe they fell out of the box, maybe they got put into a different box etc. Another person may realize that finding all of the pieces is now a fools errand, but careful analysis of the pieces we do have could reveal most of what the puzzle depicts.
Now lets complicate matters further and imagine that instead of just missing 900 pieces, you also have 3000 pieces of other puzzles mixed together with the puzzle you are trying to solve. Now if you choose to go looking for the missing pieces you may in fact find pieces that fit another puzzle altogether instead of the puzzle you are interested in.
I think this approach is a really valuable way of looking at scientific investigation. Perhaps just as valuable as the scientific method. Of course the scientific method is a different way of looking at problem solving and provides a much more detailed methodology.
There are a lot of scientists who approach scientific problems by hunting for the missing pieces (piece hunters). This usually includes people who specialize in a particular technique (remote sensing, isotopic analysis, TEM, etc.). In their world, their technique will provide the key missing pieces because the measurement has never been done before on whatever sample they are analyzing. Of course once they have found the piece (made the measurement using their favorite technique) they need to figure out how it fits. But since their entire effort has been focused on just finding the piece, they frequently look for an easy connection and write their paper.
There are other people (piece thinkers) who instead approach scientific problems by just examining the pieces (data) that has already been collected. These people find interesting connections that haven't already been made, and thus can make discoveries without finding out anything new. Of course this is usually difficult to do, since despite my callous description of the piece hunters, they usually have made most of the connections already.
Now, I don't think this dichotomy is a black and white thing. I think many of the piece hunters also spend a lot of time trying to understand the pieces already collected, and many of the piece thinkers also do their fair share of finding new pieces. Obviously, the most powerful science is done where both methods are combined and an investigation is targeted to find a specific missing piece. The problem for the piece hunters is that because of their technique specialty, they can only find certain types of pieces. If the targeted piece isn't the right kind, then they are out of luck.
Applying this whole concept to Mars, if we imagine Mars as a puzzle. We definitely have started with only a very few pieces, so it makes a lot of sense for us to focus our energies on obtaining new pieces to the puzzle. However in the last 10 years, this has resulted in a multitude of pieces - many of which don't fit into our specific Mars puzzle. So now we find ourselves in a position where piece thinking may prove more fruitful than piece hunting. In addition, I think it is time that the piece hunters sit down at the table and start putting more effort into understanding the pieces they've already collected, than simply collecting more for the sake of collecting more.
So switching back into the Gladwell terminology, I would say that Mars has changed in the past ten years from a puzzle to a mystery. More innovative thinking is needed to approach and identify the key scientific questions - and design better investigations.
So let me define the terms here. In the article a puzzle is a problem which has a definite solution where new information will yield an obvious answer. A mystery is a problem where we may in fact have too much information and may not come to a satisfactory conclusion. Gladwell argues that it is critical that we identify the particular type of problem we face (puzzle vs. mystery) because if we approach a mystery like a puzzle we will utterly fail to address it adequately.
If I may, I'll offer this analogy to make this clearer. Suppose you have a 1000 piece puzzle but are missing 900 of the pieces. You can approach this problem in two different ways - One person may decide to go looking for the missing pieces - maybe they fell out of the box, maybe they got put into a different box etc. Another person may realize that finding all of the pieces is now a fools errand, but careful analysis of the pieces we do have could reveal most of what the puzzle depicts.
Now lets complicate matters further and imagine that instead of just missing 900 pieces, you also have 3000 pieces of other puzzles mixed together with the puzzle you are trying to solve. Now if you choose to go looking for the missing pieces you may in fact find pieces that fit another puzzle altogether instead of the puzzle you are interested in.
I think this approach is a really valuable way of looking at scientific investigation. Perhaps just as valuable as the scientific method. Of course the scientific method is a different way of looking at problem solving and provides a much more detailed methodology.
There are a lot of scientists who approach scientific problems by hunting for the missing pieces (piece hunters). This usually includes people who specialize in a particular technique (remote sensing, isotopic analysis, TEM, etc.). In their world, their technique will provide the key missing pieces because the measurement has never been done before on whatever sample they are analyzing. Of course once they have found the piece (made the measurement using their favorite technique) they need to figure out how it fits. But since their entire effort has been focused on just finding the piece, they frequently look for an easy connection and write their paper.
There are other people (piece thinkers) who instead approach scientific problems by just examining the pieces (data) that has already been collected. These people find interesting connections that haven't already been made, and thus can make discoveries without finding out anything new. Of course this is usually difficult to do, since despite my callous description of the piece hunters, they usually have made most of the connections already.
Now, I don't think this dichotomy is a black and white thing. I think many of the piece hunters also spend a lot of time trying to understand the pieces already collected, and many of the piece thinkers also do their fair share of finding new pieces. Obviously, the most powerful science is done where both methods are combined and an investigation is targeted to find a specific missing piece. The problem for the piece hunters is that because of their technique specialty, they can only find certain types of pieces. If the targeted piece isn't the right kind, then they are out of luck.
Applying this whole concept to Mars, if we imagine Mars as a puzzle. We definitely have started with only a very few pieces, so it makes a lot of sense for us to focus our energies on obtaining new pieces to the puzzle. However in the last 10 years, this has resulted in a multitude of pieces - many of which don't fit into our specific Mars puzzle. So now we find ourselves in a position where piece thinking may prove more fruitful than piece hunting. In addition, I think it is time that the piece hunters sit down at the table and start putting more effort into understanding the pieces they've already collected, than simply collecting more for the sake of collecting more.
So switching back into the Gladwell terminology, I would say that Mars has changed in the past ten years from a puzzle to a mystery. More innovative thinking is needed to approach and identify the key scientific questions - and design better investigations.
Tuesday, March 29, 2011
Review of "Contemporaneous deposition of phyllosilicates and sulfates: ..."
This is a review of
Baldridge, A. M., S. J. Hook, et al. (2009). "Contemporaneous deposition of phyllosilicates and sulfates: Using Australian acidic saline lake deposits to describe geochemical variability on Mars." Geophysical Research Letters 36.
This paper came out a year before the Hurowitz et al. (2010) article that I reviewed above, and really deserves to be recognized for first discussing the topic of Fe hydrolysis as a source of acidity in martian groundwater systems, especially since the Hurowitz article does not reference it. This paper is one of the few good studies of a terrestrial analog. It is good because it uses the analog to make new and interesting hypotheses for Mars rather than studying an analog that seems similar to Mars and then not saying much of anything.
The paper examines the geochemistry of acid saline lakes in western Australia and notices that this geochemical behavior could also be happening on Mars. In the Australian lakes, saline reducing groundwater interacts with basement rocks to produce relatively Fe(II)-rich groundwater with neutral pH (6-8). However, when this water rises to the surface it becomes oxidized and is acidified through Fe hydrolysis reactions:
2Fe2+ + 1/2O2 + 5H2O ==> 2Fe(OH)3 + 4H+
The source of the acidity is either from diagenetic pyrite, sulfides in the basement rock, or oxidation of H2S. Note that none of these mechanisms create acidity through weathering of Fe-silicate minerals.
When this groundwater reaches the surface it mixes with fresh water from surface runoff and produces a series of minerals including kaolinite, sulfates, chlorides, opaline silica, Fe-oxides, jarosite, gypsum, etc.. The pH gradients created exist both with depth and laterally with the central portion of the lakes being higher pH along with the subsurface.
Applying this information to Mars, Baldridge et al. suggest that the Andrews-Hanna groundwater models would likely result in reduced neutral to high pH fluids - similar to the groundwater below the australian lakes. However, this groundwater may become oxidized and acidified as it rises to the surface if it contains enough Fe(II). They note that these environments may contain large geochemical gradients making it possible to precipitate phyllosilicates and sulfates contemporaneously.
This poses an interesting alternative to the "Bibring Hypothesis" which states that Mars went through an early phyllosilicate period with alkaline fluids then was later dominated by acidic sulfate forming fluids. I've always felt that this was way too oversimplified, and the Baldridge et al. paper clearly articulates a good reason why by showing that geochemical systems are complicated and it isn't crazy to have a single aqueous system capable of forming all of the minerals at the same time.
However, I think the Baldridge et al. paper makes the same mistake as the Hurowitz et al. (2010) paper does. On the bottom of page 4 is the following quote:
Here the idea is that you can generate acidity by dissolving Fe(II) bearing silicate minerals. As mentioned in my post about the Hurowitz article, this reaction when viewed in total is pH neutral:
2FeO(pyx, ol) + H2O + 0.5O2 --> 2FeO(OH)
It is important to keep in mind that in the Australian lakes, and in geochemical models, the only way to generate acidity through Fe hydrolysis is if you have dissolved sulfide minerals or added acidity to the solution at some point. This is the requirement for the groundwater models of Mars. However since we do not show a large enrichment of Fe over Mg and Ca in the Meridiani sediments it seems unlikely that iron sulfides have been the source of the sulfur. So in order for the groundwater models to obtain acidity, they need to incorporate large amounts of SO2 into the aquifers during rainfall and runoff. Furthermore a large portion of this acidity must be neutralized through weathering of Fe(II) rich silicates rather than Ca or Mg-rich silicates which will permanently neutralize the acidity.
Baldridge, A. M., S. J. Hook, et al. (2009). "Contemporaneous deposition of phyllosilicates and sulfates: Using Australian acidic saline lake deposits to describe geochemical variability on Mars." Geophysical Research Letters 36.
This paper came out a year before the Hurowitz et al. (2010) article that I reviewed above, and really deserves to be recognized for first discussing the topic of Fe hydrolysis as a source of acidity in martian groundwater systems, especially since the Hurowitz article does not reference it. This paper is one of the few good studies of a terrestrial analog. It is good because it uses the analog to make new and interesting hypotheses for Mars rather than studying an analog that seems similar to Mars and then not saying much of anything.
The paper examines the geochemistry of acid saline lakes in western Australia and notices that this geochemical behavior could also be happening on Mars. In the Australian lakes, saline reducing groundwater interacts with basement rocks to produce relatively Fe(II)-rich groundwater with neutral pH (6-8). However, when this water rises to the surface it becomes oxidized and is acidified through Fe hydrolysis reactions:
2Fe2+ + 1/2O2 + 5H2O ==> 2Fe(OH)3 + 4H+
The source of the acidity is either from diagenetic pyrite, sulfides in the basement rock, or oxidation of H2S. Note that none of these mechanisms create acidity through weathering of Fe-silicate minerals.
When this groundwater reaches the surface it mixes with fresh water from surface runoff and produces a series of minerals including kaolinite, sulfates, chlorides, opaline silica, Fe-oxides, jarosite, gypsum, etc.. The pH gradients created exist both with depth and laterally with the central portion of the lakes being higher pH along with the subsurface.
Applying this information to Mars, Baldridge et al. suggest that the Andrews-Hanna groundwater models would likely result in reduced neutral to high pH fluids - similar to the groundwater below the australian lakes. However, this groundwater may become oxidized and acidified as it rises to the surface if it contains enough Fe(II). They note that these environments may contain large geochemical gradients making it possible to precipitate phyllosilicates and sulfates contemporaneously.
This poses an interesting alternative to the "Bibring Hypothesis" which states that Mars went through an early phyllosilicate period with alkaline fluids then was later dominated by acidic sulfate forming fluids. I've always felt that this was way too oversimplified, and the Baldridge et al. paper clearly articulates a good reason why by showing that geochemical systems are complicated and it isn't crazy to have a single aqueous system capable of forming all of the minerals at the same time.
However, I think the Baldridge et al. paper makes the same mistake as the Hurowitz et al. (2010) paper does. On the bottom of page 4 is the following quote:
The long aquifer flow paths would also promote dissolution of Fe-bearing volcanic glasses and silicates, thereby enriching the water in Fe2+ ions. As observed in australia, Fe2+ transported in solution would eventually oxidize and precipitate Fe3+ phyllosilicates and/or oxides, while generating acidity in the upward flowing waters.
Here the idea is that you can generate acidity by dissolving Fe(II) bearing silicate minerals. As mentioned in my post about the Hurowitz article, this reaction when viewed in total is pH neutral:
2FeO(pyx, ol) + H2O + 0.5O2 --> 2FeO(OH)
It is important to keep in mind that in the Australian lakes, and in geochemical models, the only way to generate acidity through Fe hydrolysis is if you have dissolved sulfide minerals or added acidity to the solution at some point. This is the requirement for the groundwater models of Mars. However since we do not show a large enrichment of Fe over Mg and Ca in the Meridiani sediments it seems unlikely that iron sulfides have been the source of the sulfur. So in order for the groundwater models to obtain acidity, they need to incorporate large amounts of SO2 into the aquifers during rainfall and runoff. Furthermore a large portion of this acidity must be neutralized through weathering of Fe(II) rich silicates rather than Ca or Mg-rich silicates which will permanently neutralize the acidity.
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