Basic characteristic of submarine hydrothermal systems (SHS)

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The figure above shows the schematics of a typical submarine hydothermal system (SHS). The magma at the hottest zone is about 1200°C. Seawater from the sea penetrates into the crust of the spreading axis (down flows) and towards the “reaction zone” which is about ~400°C. Seawater-rock interaction happens here, the water is then released through and is cooled down rapidly by cold seawater. A quenching effect takes place here. The abundance of minerals and/or metals are also part of the system. Some of the chemical composition of a typical black- smoker type of SHS is shown here. The diagram above represent what we typically call a black-smoker, A black smoker is a type of hydrothermal vent typically found in the abyssal and hadal zones.

A black smoker from NOAA

Common pictures on SHS are generally black smokers. They appear as black chimney-like structures that emits a cloud of black material containing high levels of sulfur-bearing minerals, or sulfides. Black smokers are formed in fields, hundreds of meters wide when superheated water from below earth’s crust comes through the ocean floor. This water is rich in dissolved minerals from the crust, most notably sulfides. When it comes in contact with cold ocean water, many minerals precipitate, forming a black chimney-like structure around each vent. Effluents from black smokers are acidic (pH 2-3) and are rich with transition metals. All the fluids gives out nutrients to all the unusual organisms at the area. Google it!!!

On the other hand, a diffuse flow is an area where hydrothermal fluids flow out instead of a chimney. The fluids from here are much cooler and slower compared compared to a typical SHS. Minerals are usually left behind in this fluids. White smoke appears to come out of the sea floor, hence the term white-smokers were coined. Unlike the black smokers, the fluids coming out of here lacks minerals which comes from their black counterparts. These two type of smokers are typical in a SHS environment. It is speculated that SHS could have existed throughout earth’s ocean, this subsequently fueled the idea that life could have started here, together with the heat loving bacteria. So far, the experiments of SHS are done with simulators at laboratories mainly in Japan and the U.S only. Research using simulators usually utilizes basic chemicals exposed to heat and pressure similar to the vent system (so far the black smokers). Another area of interest is to see the survivability of common bio-molecules such as amino acids in SHS simulators. This is important as data from these kind of experiment usually presents the thermal and pressure limits of the chemicals used in life’s processes. We know now that amino acids (not all) can survive in SHS simulators, which gives a good account to SHS being a good spot to origins. On the other hand, genetic materials (DNA and RNA) are instantly destroyed when exposed to the simulators. This proves to be a difficult scientific problem to solve so far.

In the next post i will be posting briefly about the LOST CITY type of hydrothermal systems, an entirely unique system and will follow with the various kind of SHS simulators i have used before.

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Hydrothermal vents vs. Miller-Urey experiment

SHS: Submarine Hydrothermal Vents

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MIller-Urey experiment (Click on the image for more details)

Previously, i showed how the link between hydrothermal vents and origin of life is fueled by the discovery of hyperthermophiles. In todays post. i will be showing the limitation of the Miller-Urey model and will discuss a little about how SHS can be a good site for origins (and their limitations too). 

Miller and Urey both designed their experiment assuming that the primitive atmosphere was reducing. This was a valid assumption at that time, and organic compounds are formed better in a reducing conditions. However, this reducing atmosphere scenario has changed, most scientist nowadays would envision a more redox neutral atmosphere. This is because there are no evidences of a reducing atmosphere documented in the rocks[1,2,3]. However, there is a small chance that a reduced atmosphere could happen for a short  period of time in the presence of a meteorites impact or vapors from an erupting volcano[4]. Also it is worth noting, because there is lack of ozone layers during those periods, UV rays could have destroyed the biomolecules in the atmosphere as soon as they are formed. All this leads that the prebiotic atmosphere is limited in the sense of origins; moreover this biomolecules needs to be protected by the UV rays [5]; hence a SHSs’ reducing powers and its UV cloaking ability makes them an ideal spot for origins. The reducing conditions in hydrothermal vents (before the discovery of Lost City Hydrothermal field) is fueled by it reduced minerals which could act as a template for various catalytic activity [6,7,8,9,10] including polymerization.

SHS is also the only place that primitive life forms could have been protected during an event of meteorite shower and/or partial vaporization of the ocean[5]. Although, SHS could well be a spot for origins, critics often cite that residence times in axial hydrothermal environments range from years to decades, ( in other word, the time spent by fluid in the hydrothermal vents is long) while those in lower temperature off-axis diffuse flow systems may be on the order of thousands of years. These residence times are impossible to model experimentally, the effects of long residence times in SHSs are not generally considered in SHS experiments. This is one of the major limitation for experiments on SHS simulation.

1. Lambert, I.B, Donnelly, T.H, Dunlop, J.S.R and Groves, D.I (1978) Stable Isotope Compositions of Early Archaean Sulphate Deposits of Probable Evaporitic and Volcanogenic Origins: Nature, v.276,p.808.

2. Dimroth, E and Kimberley, M.M (1976) Precambrian Atmospheric Oxygen: Evidence in the Sedimentary Distributions of Carbon, Sulfur, Uranium and Iron: Canadian Journal Earth Science, v.13,1976, pp.1161-l185.

3. Zeschke, G (1960) Transportation of Uraninite in the Indus River, Pakistan: Geological Society of South Africa v.63, p.87. 

4. Johnson, A. P, Cleaves, H. J, Dworkin, J. P, Glavin, D. P, Lazcano, A and Bada, J. L. (2008). The Miller volcanic spark discharge experiment. Science, 322(5900), 404–404. 

5. Sleep, N. H, Zahnle, K. J, Kasting, L F and Morowitz, H.J (1989) Annihilation of ecosystems by large asteroid impacts on the early Earth, Nature 342, 139-142. 

6. Wachtershauser, G (1988) Before enzymes and templates: Theory of surface metabolism, Microbiology Review. 52, 452-484.

7. Wachtershauser, G (1988) Pyrite formation, the first energy source for life: A hypothesis, Systematic and Applied Microbiology 10, 207-210.

8. Wachtershauser, G (1990) The case for the chemoautotrophic origin of life in an iron- sulfur world, Origins of Life and Evolution of the Biosphere 20, 173-176

9. Russell, M. J, Hall, A. J and Turner, D (1989) In vitro growth of iron sulphide chimneys: Possible culture chambers for origin-of-life experiments, Terra Nova 1, 238-241 

10. Kadko, D and Butterfield, D.A (1998) The relationship of hydrothermal fluid composition and crustal residence time to the maturity of vent fields on the Juan de Fuca Ridge. Geochimica et Cosmochimica Acta 62:1521– 1533

11. Turekian, K.K, Cochran, J.K (1986) Flow-rates and reaction-rates in the Galapagos Rise spreading center hydrothermal system as inferred from Ra-228/Ra-226 in vesicomyid clam shells. Proceedings of the National Academy of Sciences of the United States of America, 83:6241–6244

12. Johnson, H.P, Pruis, M.J (2003) Fluxes of fluid and heat from the oceanic crustal reservoir. Earth and Planetary Science Letters 216:565–574 

Origin of life and heat loving bacteria

SHS=Submarine hydrothermal system

In the last post, i discussed briefly about SHS, here i will be posting some details on why SHS is suitable for life to start. I will be going one by one to help sell the idea on why SHS is good for origins and will show their shortcoming as well

Some of the accepted hypothesis on hyperthermophilles phylogenetic tree. The positions are based on 16S/18S rRNA phylogenic positions29. The root for trees A and B are placed in the bacterial branch30, hence making LUCA a hyperthermophile. In C, the root is placed under the eukaryotic branch making the hyperthermophile a last common prokaryotic ancestor (LCPA)31. D is unrooted, making the LCPA a mesophile.  Adapted from DeLong, E.F, Wu, K.Y, Prezelin, B.B and Jovine, R.V.M (1994) Abundance of Archaea in Antarctic Marine Picoplankton. Nature 371, 695–697
Some of the accepted hypothesis on hyperthermophilles phylogenetic tree. The positions are based on 16S/18S rRNA phylogenic positions29. The root for trees A and B are placed in the bacterial branch30, hence making LUCA a hyperthermophile. In C, the root is placed under the eukaryotic branch making the hyperthermophile a last common prokaryotic ancestor (LCPA)31. D is unrooted, making the LCPA a mesophile.
Adapted from DeLong, E.F, Wu, K.Y, Prezelin, B.B and Jovine, R.V.M (1994) Abundance of Archaea in Antarctic Marine Picoplankton. Nature 371, 695–697

One of the biggest reason associated with origins and SHS, is related to hyperthermophiles. They are microorganism that strive at extreme heat. These organism cultivated from the vents areas could strive at 110 ℃ of heat, which could flourish at temperature up to 110℃. Several authors1,2,3, have proposed that these microbes could have close relation to LUCA. This hypothesis derives from the construction of archaeal and bacterial phylogenetic trees based on 16S rRNA sequence comparisons4. Hyperthermophiles are clustered at the base of these trees and many of their branches are short, suggesting that they have conserved ancestral phenotypic characters3. However, there are also contradicting studies, which indicate that these microbes posses  “missing” enzymes, that uses other energy co-factors, instead of conventional ATP molecule. In other words, this finding shows that these enzymes have adapted to function at high temperature thus indicating that these microbes are more recent than suggested5.

A limitation to this finding is that it assumes that ATP have existed long in time; this argument can be refuted if one also imagine that ATP is also a recent and high adapted energy co-factor in life. This hyperthermophiles, was the first hint which made SHS suitable for origins; however the theory is not limited to this reasons only.

  1. Baross, J.A, and Hoffman, S.E (1985) Submarine hydrothermal vents and associated gradient environments as sites for the origin and evolution of life. Origins of Life and biosphere 15, 327–345.
  2. Pace, N.R (1991) Origin of life–Facing up to the physical setting. Cell 65, 531–533.
  3. Forterre, P (1996) A hot topic: the origin of hyperthermophiles. Cell, 85(6), 789–792.
  4. Stetter, K.O (1994) In Early Life on Earth, S. Bengston, ed. (New York: Columbia University Press), pp. 143–151
  5. Siebers, B and Hensel, R (1993) Glucose catabolism of the hyperthermophilic archaeum Thermoproteus tenax Microbiology Letters. 111, 1–8.
  6. Forterre, P, Confalonieri, F, Charbonnier, F and Duguet, M (1995) Speculations on the origin of life and thermophily: review of available information on reverse gyrase suggests that hyperthermophilic procaryotes are not so primitive. Origins of Life and biosphere. 25, 235–249.

Submarine Hydrothermal system (SHS) and the link to origin of life

http://www.whoi.edu/cms/images/lstokey/2005/1/v41n2-tivey1en_5063.jpg

Plate tectonic is the theory which unified on how the earth worked. The theory has always been there (since 1879)1,2 and was only accepted in the 1950‘s. The theory also predicted the existence of hydrothermal vents; a deep-sea hot springs is formed when cold seawater seeps into magma-emitting cracks on the oceanic surface, heats up, and rises. Although scientists had been actively searching for vents since the early 1960s, it wasn’t until the 1977; when the Galápagos Hydrothermal Expedition led by Richard Von Herzen and Robert Ballard of the Woods Hole Oceanographic Institution, that confirmed their existence using the famous submersible, Alvin ,3,4.

The relationship between SHS and origin of life on the other hand, first came out through Jack Corliss, John Baross and Sarah Hoffman5. They claimed that the conditions surrounding the vent area provided all the conditions for life’s creation on earth. Over time this idea has sprouted and have been elaborated with many in-situ integration with simulation data. I will elaborate more on this in the next post.

  1. Darwin, G.H (1879) On the procession of viscous spheroid, and on the remote History of the Earth.Philosophical Transactions of the Royal Society of London Vol. 170, 447-538
  2. McKenzie, D. P (1969) Speculations on the consequences and causes of plate motions. Geophysical Journal International, 18(1), 1–32.
  3. Corliss, J. B. J, Baross, J.A and Hoffman, S.E (1981) An hypothesis concerning the relationship between submarine hot springs and the origin of life on Earth.  Oceanologica Acta 4, 59-69.
  4. Corliss, J.B, Lyle, M, Dymond. J and Crane, K (1978) The chemistry of hydrothermal mounds near the Galapagos Rift. Earth and Planetary Science Letters, Volume 40, Issue 1,12–24.
  5. Corliss, J.B, Baross, J.A. and Hoffman, S.E (1981) An hypothesis concerning the relationship between submarine hot springs and the origin of life on Earth, Oceanologica Acta 4, 59–69

Free online course on Astrobiology and the search of life.

Hello world. Have you guys heard about Coursera. It’s basically a place where you can learn stuff for free (tons of it). They are now offering a course on my field entitled “Astrobiology and the Search for Extraterrestrial Life”. Click here. The course is 5 weeks long and starts on the 28th of January 2013. So i am giving you a head start here. Register in the link above, and you will get an email remainder before the courses starts. The instructor is Charles Cockell whom is a Professor of Astrobiology at the University of Edinburg, and more importantly you don’t need any background knowledge to learn this.

Check out the preview for the program

This is what you are going to learn

Week 1: What is life and what are the definitions of life? What do we know about the origin of life and what are the current hypotheses for how it originated on the Earth?

Week 2: What was the environment of early Earth like when life first emerged and what do we know about life on the earliest Earth? How did life evolve to cope with survival in extreme environments? What have been the major evolutionary transitions of life on the Earth?

Continue reading “Free online course on Astrobiology and the search of life.”

Geological time scale part 2

Before starting the second part, i  would like to apologize for the delay. I was not super busy or anything, just being plain lazy without any excuses.

Moving on, When did life actually started? No one can actually tell. However scientists believe that life could have started or originated on multiple occasion and scenarios, only to be denied by major impacts. Despite this, it is speculated that life must have started around 3.8 billion years ago, when the LHB seized.

As mentioned in the previous post, the Archean period indicates, that earth has more water and minerals to make life plausible but, before that the atmosphere and the ocean has to form and cool off from HLB impacts. Only after this events, life could kick-start. Prebiotic chemistry happened during this time where the formation of lipids and peptides aggregates were formed. The idea of a “prebiotic soup” also must have happened here too. Many models were designed to imitate this period as well.

The protocell or LUCA (last universal common ancestor); could have emerged right after the prebiotic chemistry has taken place with metabolic diversification (which is about 3.8 -2.5 billion years ago). However, these are all scientific hypothesis, there are no fossilized records what so ever. Overall the origin of life idea is based on several hypothesis to build the prebiotic world and it’s chemistry. This grey area is where many chemical astrobiologist (like me) are focusing on. The idea however, is heavily supported by present knowledge of chemistry and geology with the power of models.

The earliest Stromatolites which is considered as the earliest micro fossils we have, is hypothesized (with heavy dispute) to have occurred right after this . The cyanobacteria rose with the power of photosynthesis giving an influx of oxygen to earth’s atmosphere, the very reason we have oxygen now. However, it should be noted that oxygen is toxic, meaning that other life forms utilizing non- oxygen metabolism during that time, must have went extinct without evidence. The Proterozoic eon starts here. The Cambrian explosion also starts here with the increasing of oxygen, leading to life forms which were well fossilized such as Opabinia and Marrella. Watch the video above to see how these creatures look like.

There are plenty of scientific evidence here. I will not be elaborating further on what happened after this. Many studies have been done, it is an establish science. We pretty much know what happened after the Cambrian explosion, but not what happened before that.

That’s all for now. The next post is about the possible sites of life’s origin.

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Geological time scale (part 1)

I first knew about the geological time scale during my college years, back then the only geological time i knew was “Jurassic” due to a certain Hollywood movie. Learning it was fun but memorizing it for exams was horrible. The lecturers will first show the scale like the one here (very very boring btw), and they will explain one by one what happened with pictures of dinosaurs, plants, ancient humans and etc. It was remarkable, but how did geologists came to this scale always puzzled me, it still does, as we have loopholes in it too. The scale is basically a convention agreed by geologists based on research which were agreeable from time to time.

Here i will briefly explain some key events and how they got there. Most importantly i will put emphasis on how and when life started, the rest is evolution which you can read/view elsewhere. I will be also breaking this topic to a few parts for easy understanding.

Lets start,

After the big bang, the HADEAN period named after Hades begin. The sun was already formed and the rise of giant planets (Jupiter and Saturn) could have happened during this time. This is based on “numerical models“. After the formation of Mars, earth was finally formed in it’s hottest state (hot as hell). It is also postulated that the moon was also formed right after this, and her origins came from earth. Check out the video below on how this could have happened

From here on, our primitive atmosphere begin to arise, which is absolutely hypothetical in case you were wondering. After this particular sequence of events, the building of the habitable earth begins. The first proto ocean were already in play after the cool down effects on earth . There are some speculation that life could have started here; but right after this, the late heavy bombardment (LHB) of comets and meteorite came showering on earth, the planet was destroyed, water evaporated completely and it was a mess. This phenomena is also observable on the moon .If you have wondered why the moon has craters, its because of LHB (despite not having tectonic plates etc).

Now, The ARCHEAN period begins, which is generally the post HLB. Earth during this time has a lot of minerals and more water because of the LHB. In other words, she has received more materials to allow life to flower.

The rest of story is to be continued in the near future, stay tuned

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History of Earth as a clock

The fossils records were the only prove when it comes to origin of life and its evolution, that was the past. With radioisotopes dating we have known more

Cellrelics needs your help! If you click on any of the social networking connections below, or share this post with a friend in any way, it will start a chain reaction of fun and knowledge across the world. Many thanks for reading! and Alexa, i hope you’re watching this, need some love here

Cellrelics wishes you a Happy New Year

Happy new year. I hope 2012 wil be an eventful and fruitful year to all my readers. Thank you for following my humble writings. Below is a 2011 review of the blog

The WordPress.com stats helper monkeys prepared a 2011 annual report for this blog.

Here’s an excerpt:

A San Francisco cable car holds 60 people. This blog was viewed about 1,600 times in 2011. If it were a cable car, it would take about 27 trips to carry that many people.

Click here to see the complete report.