"to seek out new life" even if not carbon-based. . .

To me as a geologist, one of the most intriguing Star Trek (original series) episodes is “Devil in the Dark” (Season 1, Episode 25), which I saw again in rerun last weekend:

Spock: “Life as we know it is universally based on some combination of carbon compounds, but what if life exists based on another element? For instance, silicon.”

The "Devil in the Dark" is the "Horta", a mobile living sentient blob that tunnels through rock in the subsurface of planet Janus 6, killing human miners who unknowingly destroyed its spherical eggs. The Horta is not an organic carbon lifeform, but instead is silicon-based. At the time of this episode's first airing in 1967, almost 48 years ago to the day, I had not studied geology yet and was unfamiliar with the silicon basis of most Earth-forming minerals, so the geologic significance was lost on me. Now, however, I appreciate the scientific/geologic foundation behind the concept of the Horta. This story is really an imagination of an alternate or opposite reality, kind of like a planetary Bizarro world (reference either Seinfeld episode, “Bizarro Jerry” Season 8, episode 3, or Bizarro of the Superman universe). 

Mr. Spock (Leonard Nimoy), communicating with the Horta through a Vulcan mind meld.

The home planet of the silicon-based Horta was not a Class M or Earth-like planet; according to the internet fan site Memory Alpha, Janus 6 was geologically inactive and had no atmosphere. Our own knowledge, so far, of unusual chemistry or processes in organic life is from Earth environments beyond the comfort level of humans, such as habitats that lack oxygen or have extreme cold or hot temperatures. "Extreme" biochemistry goes beyond chemical processes and includes incorporation of non-typical elements in genetic material: in saline Mono Lake, California, arsenic has been found to replace phosphorous in DNA and proteins of the bacteria GFAJ-1. The arsenic-phosphorous and silicon-carbon exchanges are examples of chemical swaps of elements in the same periodic table group (column) with similar outer electron shells. The article points out, however, that a total substitution of one element for another in Earthly biota would doom an organism.

Is it possible that in other parts of the universe we can find elements we have not imagined, like the Star Trek element pergium mined on Janus 6 or the warp-core fuel dilithium? (Fictional dilithium is an element, not a molecule of two lithiums.) Despite the expanse of the universe, we do understand the formation processes of elements produced during pre-supernova star evolution (hydrogen, helium, carbon, neon, oxygen, silicon, iron) and of higher mass elements in post-iron nova/supernova stellar rebound explosions . However, I am guessing there may well be new minerals, not known on Earth, on extraterrestrial planets and moons. As I mentioned in my blog post of November 5, 2014, on the “Deep Carbon Through Deep Time” short course, Robert Hazen described how species of minerals have appeared and evolved on Earth through time in response to surface and subsurface processes. Mineral evolution and resulting mineral assemblages on other extraterrestrial bodies may be different based on element distribution within proto-solar system clouds, resulting initial composition of planetary and lunar bodies, presence or absence of tectonic processes, extremes of temperature and pressure. And this includes organic minerals: Hazen pointed out there are such species since the definition of a mineral is now something that creates a diffraction pattern (Hazen and others, p. 32, Carbon in Earth, Reviews in Mineralogy and Geochemistry, vol. 75). Differences in mineral evolution, in addition to non-Earth-like extreme physical conditions, may in turn give rise, I imagine, to different microbes and pre-biotic molecules, since it is known that on Earth minerals serve as electron donors, or energy sources, for lithoautotrophic microbes (Colwell and D’Hondt, p. 558, Carbon in Earth).

Speaking of alien life, Spock's physical make-up also includes an alternate chemistry. Vulcan blood is green because it is copper-based. If analogous to human Earthling blood, the copper would be chelated in the middle of the square porphyrin (tetrapyrrole) molecule in place of iron. In people with lead poisoning, lead replaces the iron, and, logically, a simple blood density test can identify the problem. The porphyrin structure that is part of the chlorophyll molecule in plants has magnesium as the chelated metal. However, during organic diagenesis and petroleum formation, vanadium and nickel from pore waters in sediments replace the magnesium; the proportion of V to Ni [V/(V+Ni)] in petroleum porphyrins depends on the oxidation/reduction potential (oxic vs. anoxic) of the sediments and can be used as a paleoenvironmental indicator.  (The Biomarker Guide: Biomarkers and isotopes in petroleum systems and Earth, 2005, by Kenneth Peters, Clifford Walters, J. Michael Moldowan). 

Chief Mining Engineer Vanderburg in “Devil in the Dark”:  ". . . Look, we didn't call you here so you could collect rocks." 

Geologists on the starship Enterprise? There is one original-series Star Trek episode in which a crew member is identified as a geologist (“That Which Survives”, Season 3, Episode 17). His character name was even listed in IMDB.com for several years as “Lt. D'Amato, Geologist”. But D’Amato, geologist on the Away Team, not in any previous episodes in the series, meets his demise, despite wearing a blue shirt, within the first 10 minutes of the story. . . saw that coming light-years away!

When I started college in fall 1969, I had been an avid follower of the US space program and thought I might major in Astronomy, Russian studies or Asian studies. I ended up majoring in History with a minor in Geology, once I realized how interesting mineralogy could be. In hindsight, I think my original interest in majoring in Astronomy was really an interest in Planetary Geology. (I was a bit disappointed to realize that academic astronomy is actually physics and math in disguise, and this was when the college math department computer was a single-job card-loading Fortran machine! Syntax errors-Aaargh!) However, in 1969, despite the first Apollo landing in July, and three years of Star Trek, a separate university concentration in Planetary Geology was not yet off the ground.

I close with a nod to Leonard Nimoy (March 26, 1931 – February 27, 2015): you will “live long and prosper” in the minds and hearts of those who dream of, imagine and yearn to explore the wonders of the universe. An excellent blog post by a geologist on Nimoy/Spock as an inspiration and role model for young scientists can be found at http://blogs.agu.org/magmacumlaude/2015/03/05/importance-fictional-role-models/ . (I actually really separately, before reading Jessica's blog and without mind meld, started writing this post and had included a photo of Spock with the Horta and the reference to geologist D'Amato. Explorers thinking alike!)

Pennsylvania anthracite culm heaps: A burning issue

In the month(!) since my last blog post, I have been busy doing other writing: finishing up the first draft of a conference paper and writing an article on “Titanic Coal” for The Society for Organic Petrology (TSOP) spring newsletter. The latter will be posted on this blog on April 15, the anniversary of the sinking. In researching what was known about sources/amount of coal on the Titanic, I found that there is strong evidence from crew survivors that a fire smoldered in piled coal in one of the fuel bunkers. Apparently coal fires were not uncommon onboard steamships or in coal waste heaps. Here in eastern Pennsylvania, coal waste dumps are called culm heaps or culm banks.  

The first time I heard the word “culm” was way back in the summer of 1961. My family had just moved to Poughkeepsie, New York, about 75 miles north of New York City. My father had a new job with Daystrom-Weston there. However, in the middle of the summer, the company division my father worked for was moved to Archbald, Pennsylvania (PA), between Scranton and Carbondale in the Northern Anthracite coalfield. So, one weekend, we (mother, father, four children ages 3-10) drove three hours west to the Scranton area to check it out. Saturday was rainy and dreary, but Sunday was clear with a better view of the countryside. Memorable were large, taller-than-houses black steaming piles, alongside or easily seen from the road. I asked my father what they were; he told me culm heaps, waste from the coal mines.

"Burning culm dump, Scranton, Pennsylvania, United States. Culms are huge dumps of coal mine waste some of which burn incessantly." Postcard, 1908.

https://commons.wikimedia.org/wiki/File:Burning_Culm_Dump,_Scranton,_PA.jpg

Although fire in piled coal can start spontaneously, The Scranton Times-Tribune recently reported in January 2015, that the PA Department of Environmental Protection says most culm fires these days start from people burning trash near the heaps (http://thetimes-tribune.com/news/dep-archbald-culm-fire-likely-quenched-1.1812321). The article states that there are at least 80 coal fires, either in culm dumps or underground mines, in Pennsylvania. Culm fires are a source of greenhouse gases in general, plus give off carbon monoxide, hydrogen sulfide, and various toxic trace elements (http://thetimes-tribune.com/news/culm-dump-fire-still-burning-in-fell-twp-1.1642374), and may pose not just an environmental danger to nearby residents but also the danger of setting adjacent coal seams on fire.  Those articles plus http://thetimes-tribune.com/news/local-history-coal-fires-plagued-the-region-for-decades-1.1671355 describe various methods to extinguish culm fires and emphasize that it is both difficult and expensive to put out such fires for good.

Fell Township, PA, coal waste dump fire, February 2014, The Scranton Times-Tribune.

Pennsylvania culm heaps are a mixture of waste shale and mixed coal-shale fragments; John Oelbracht, plant manager at Westwood Generating, described it as "'rock with some coal stuck to it'" (http://powersource.post-gazette.com/powersource/policy-powersource/2015/01/06/Waste-coal-plants-a-poor-fit-with-carbon-emission-rules/stories/201501060014). Westwood Generating is one of 14 waste coal power plants in Pennsylvania that use culm as fuel in an effort to clean up the anthracite region dumps. The Pittsburgh Post-Gazette article points out that waste coal power plants, employing a fluidized bed system specifically built to burn culm, may not meet new US Environmental Protection Agency Clean Power Plan carbon-dioxide emission standards, but could apply for a legal exemption on the grounds that CO2 produced by burning culm would not be more than emissions from smoldering culm if left in place. In addition, using culm then removes an environmental chemical hazard from the landscape.

So. . . did we move to Scranton? No. My parents decided (or maybe my mother made the final decision) to move back to our old neighborhood in New Jersey, and my father commuted weekly by car to Scranton. Six months later in February 1962, he got a new job in Chicago, and commuted weekly by plane until the school year ended and we all moved out to join him (only once in several relocations did my parents move us in the middle of the school year). Did all this moving bother me? No. While I do not have a "hometown", I have experienced living in several communities and states, and had a variety of opportunities that I might have missed if I stayed in one place.

"Upon the Road of Anthracite"

I was recently watching A Room with a View, the 1985 Ivory-Merchant film dramatization of E. M. Forster’s Edwardian-period novel. The stellar cast includes Helen Bonham-Carter, Judi Dench, Maggie Smith, and others recognizable from the last 30 or more years of British film. Skipping a plot synopsis and getting right to the point, in one short scene Maggie Smith's character is traveling by train in England. In her compartment, she is sitting by the window, which is open. At one point, she uses her handkerchief to dab something out of her eye. The man sitting opposite her politely volunteers to close her window. 

Her little move to wipe her eye, and the implication that particulates are coming in the window, was a realistic aspect of train travel in the era of coal-powered steam engines. Steam engines were especially sooty. Using anthracite coal, rather than bituminous, however, reduced the particulates. The Delaware, Lackawanna and Western Railroad (DL&W), serving New York, New Jersey, and Pennsylvania, and which owned anthracite mines in Pennsylvania, used this advantage of anthracite combustion in an early twentieth-century ad campaign promoting its clean ride. It was the first ad campaign using a "fictional character based on a live model" (http://en.wikipedia.org/wiki/Phoebe_Snow_(character)). Phoebe Snow was always dressed in white and could disembark the train at her destination as pristine as when she boarded. 

Postcard, by Anthracite Museum Press, Scranton, PA, showing a 1910 DL&W Phoebe Snow advertisement.

Coal rank based on calorific value and fixed carbon content (Figure 5), from Stanley P. Schweinfurth, 2009, An introduction to coal quality-Ch. C: US Geological Survey Professional Paper 1625-F.

With high carbon content and low volatile matter, anthracite burns more cleanly than bituminous coal. It is well-suited for boilers associated with engines and space heating. However, it does not soften and vesiculate ("coke") like bituminous coals; therefore, anthracite cannot be used to make coke (porous, high strength product with high carbon content) for steel making. Other limiting factors for anthracite utilization are that it is much less abundant than bituminous coal and, in Pennsylvania, was previously mostly produced from underground mines, which have higher production costs and are more dangerous than surface mines. One of the last big institutional US customers of Pennsylvania anthracite was the New York City School system, but they retired their old coal-fired furnaces in the late 1990's. 

However, PA anthracite is still used in domestic home heating in the NE USA, interestingly common in Amish homesteads. The clean-burning characteristics apparently make it an attractive fuel for Chinese industry, but the following blog article explains that the export market, as of 2014, is dominated by Russia.
(http://www.philly.com/philly/blogs/inq-phillydeals/Siberia-hard-coal-crushes-Pa-exports-Amish-boost-US-demand.html)

Rant on fossil fuel age inaccuracies on the web!

In the last couple weeks, I have found a few websites with gross inaccuracies about the geologic age of fossil fuel resources. I was disappointed, but just rolling my eyes, after the first finds one day, mostly because they were not science websites. But the second incident pushed me over the threshold of frustration, partly because it was the second occurrence in so many weeks and partly because it was on a state government energy education webpage.

The first were on various Pennsylvania anthracite region websites, including http://www.blaschakcoal.com/wp-content/uploads/Anthracite-Advantage-Fact-Sheet1.pdf and http://huberbreaker.org/home/history/history-of-anthracite-region/. Blaschak is an anthracite coal producer in northeastern Pennsylvania (PA), USA. Although I found their fact sheet through Google, I cannot find it from within the Blaschak website, a well-done website that describes the current mining practices, reclamation, and coal quality data. On the fact sheet, however, they state "Today, anthracite is the oldest, hardest and cleanest type of coal". The Huber Breaker historical site also calls anthracite the oldest type of coal ("that is, it took nature the longest to form"). About.com (http://energy.about.com/od/Coal/a/Anthracite-Coal.htm) writes

"Anthracite is mined from the oldest geological formations, and therefore has spent the longest time underground and been subjected to the most pressure and heat, making it the most compressed and hardest coal. Hard coals contain greater potential to produce heat energy than do the softer, geologically 'newer' coals." Yikes!

In fact, in Pennsylvania, the rock formations of both the anthracite coals (eastern PA in Valley and Ridge physiographic province) and bituminous coals (western PA in Allegheny Plateau province) are time equivalents (p. 21 [page 2 of .pdf]: https://www.dep.state.pa.us/dep/deputate/minres/bmr/beneficial_use/10%20CHAPT%202/Chapter%202%20final.pdf). The higher rank of PA anthracite is due to increased deformation and probably advective (heated) groundwater flow (Harrison, M. J., Marshak, S., and Onasch, C. M., 2004, Stratigraphic control of hot fluids on anthracitization, Lackawanna synclinorium, Pennsylvania: Tectonophysics, v. 378, p. 85-103). The coals were deposited during the Pennsylvanian subperiod (323-299 Ma*) of the Carboniferous Period. The folding and thrusting that created the Valley and Ridge province occurred during the late Paleozoic Alleghanian orogeny, but was west of the most intense deformation and metamorphism in the Piedmont.

More concerning is information in the fossil fuel chapter of the award-winning "Energy Quest" education pages (http://energyquest.ca.gov/about.html) of the California Energy Commission (http://www.energyquest.ca.gov/story/chapter08.html). The page says 

    "There are three major forms of fossil fuels: coal, oil and natural gas. All three were formed many hundreds of millions of years ago before the time of the dinosaurs – hence the name fossil fuels. The age they were formed is called the Carboniferous Period. It was part of the Paleozoic Era. "Carboniferous" gets its name from carbon, the basic element in coal and other fossil fuels. . . . Some deposits of coal can be found during the time of the dinosaurs. For example, thin carbon layers can be found during the late Cretaceous Period (65 million years ago) – the time of Tyrannosaurus Rex. But the main deposits of fossil fuels are from the Carboniferous Period."

This is very incorrect! The major coal deposits of western Europe and the eastern US are indeed Carboniferous in age. BUT, world-wide there are coals as old as Devonian, and peats and soft brown coals as young as Pleistocene (epoch of recent Ice Ages). Texas and North Dakota lignites (western US) are Paleogene (just after dinosaurs); "Gondwanan" coals of India, Australia, Antarctica and Africa are Permian (Taylor, G. H., Teichmüller, M., Davis, A., Diessel, C. F. K., Littke, R., Robert, P., 1998, Organic petrology: Gebrüder Borntraeger, Berlin, 704 pages) (see also Geologic Time Scale link at bottom). Petroleum (liquid or gas) has been found in 1 billion year old rocks (thinking of the Nonesuch Formation, White Pine, MI); California's most hydrocarbon-prolific formation is the much younger Miocene Monterey Formation, whose age ranges from 15-4 Ma (http://archives.datapages.com/data/pac_sepm/030/030001/pdfs/87.htm).

I have no idea where these webpage authors got their information! In a deep basin where sediments are sequentially buried by younger and younger rocks, organic matter in the older rocks would be more indurated or metamorphosed. But those discussing anthracite seemed to have gone backwards and assumed that higher coal rank means older, without looking up the actual age of the anthracite coals compared to the bituminous ones on the other side of the state: it is other factors like maximum burial depth, deformation and tectonics that caused the difference in PA coal rank.

The California energy page information is even more disappointing, given the excellent resources right there in state: the California Geological Survey, state public and private universities, and the oil industry itself. I found the webpages because a technology education teacher acquaintance uses them as source information for students on types of conventional and alternative energy. I did send the Energy Quest media contact an e-mail describing the inaccuracy and suggesting (hoping) they contact either the state survey or a university geology department to get their geology information in order.

*Ma= million years ago; Here is a link to the geologic time scale:
www.geosociety.org/science/timescale/timescl.pdf

Wax and Wonderful New Year!

Happy New Year to all! We are now past the anticipation of December, in Western culture, for Christmas and other religious holidays (gatherings of family and loved ones, traditions of gift-giving, greetings of love and friendship), and anticipation for the end of one calendar year and the hopes of the new year. We have also survived the long darkness of the northern winter solstice and welcome slowly lengthening daylight.

At this time of the year, candles have long been popular, originally as a source of light during the long dark cold nights. Our lights of winter and winter holidays have not just been utilitarian, so we can actually see or find our way in the physical darkness, but carry symbolism of hope, knowledge, goodness, truth, “a light shining in the darkness”. Before electrification, candles provided a slow, long-burning source of light and the portability that a campfire or hearth could not. Candles, in regions with reliable electrical service, are now primarily for decoration or ambience, although here in the eastern US, we keep spare candles in case of hurricane/ice storm/blizzard power outages. Certainly no one, hopefully, is using real candles as lighting on interior Christmas trees anymore!

Candles these days are primarily made of paraffin wax, a soft malleable long-chain hydrocarbon derived from coal or petroleum. Beeswax is occasionally used in artisan candles, and, formerly, rendering of animal fats was a major source of candlewax.

Waxy paraffins are generally longer chain hydrocarbons of the alkane series CnH2n+2. Simply, the carbons are linked by single covalent bonds to each other in a chain, and a hydrogen is single-bonded to each of the two remaining bond sites of each carbon; the end carbons have three hydrogens. The first four alkanes in this series (methane, ethane, propane, butane) are gases at room temperature; the next alkanes to C17H36 are liquid. The waxy solid alkanes (or paraffins) have a carbon number of 18 or higher.

Example of alkane structure, ethane C2H6 (chemwiki.ucdavis.edu)

My favorite mental picture of waxy crude hydrocarbons comes from Hollis Hedberg’s seminal 1968 paper on  “Significance of high-wax oils with respect to genesis of petroleum” (American Association of Petroleum Geologists Bulletin, vol. 52, p. 736-750): “High wax content is a distinctive and readily detectable characteristic of many petroleums, most simply manifested by a tendency for the oil to congeal at relatively high atmospheric temperatures (high pour-point). This tendency is often dramatically demonstrated by drill-stem tests in which the fluid blown into the air at reservoir temperature falls back with a dull thud as a solid on the derrick floor.”

But despite the New Year, there is still a lot of cold winter, actually most of astronomical winter, left to “weather” since the spring equinox is still almost 3 months away. For two years, I lived in Norway, “Land of the Midnight Sun”, although in Oslo, it is never 24 hours of darkness (about 6 hours daylight in late December). By February, the continuing cold, lack of daylight, lack of holidays until Easter, can make the populace ‘vaersyk’ (weather-sick or, in modern lingo, to have seasonal affective disorder), despite their enthusiasm for winter sports, with an unfortunate high suicide rate. Here in eastern Pennsylvania, 70 miles due west of New York City, we wait now in anxious anticipation of whether Heikki Lunta, the Finnish-American god of snow from the blizzardy Upper Peninsula of Michigan (lived there the record-snowfall winter of 1978-79), will taunt us this year as he did last (I was running out of places to pile up what I shoveled off the sidewalk). 

Eventually it will be spring, with visible new life, new beginnings, less darkness. We can trade our long-chain-paraffin candles for short-chain-propane-powered barbeques and easy outdoor social gatherings in comfortable weather. However, we should actually never wait for a calendar date for new beginnings or steps toward improvement in the human condition, but make it a year-round goal. Best wishes for joy, good health, and peace in 2015!

A side of bacon...or algae?

In mid-November here in Easton, Pennsylvania, before winter temperatures descended on us with a thud and preceding the turkey frenzy of Thanksgiving, Bacon Fest was held in our center square. (Through spring into early fall, our Farmer's Market, the nation's oldest continuous open-air market (~1752) is held in the square.) I did not go to Bacon Fest this year, but last year my dog and I enjoyed some delicious bacony macaroni and cheese, looked at the little piggies before the piglet races, and drooled over beautiful imaginative bacon-ingredient cupcakes in the baking competition. I did not realize until a few years ago, that some people are crazy for bacon!

Last entry, I mentioned the petroleum potential of amorphous organic marine snow. Sometimes I have used frying bacon as an analogy, for non-scientists, to describe petroleum generation from kerogen (insoluble organic matter residue in rocks): heat up the fatty bacon and liquid grease is produced, some greasy gas, and eventually one ends up with more grease and a burnt up solid, if the cook has not been paying attention. Same in a rock: oil-prone organic matter, such as lipid-rich plankton, algae, marine snow, spores/pollen, will, as temperature slowly increases with deep burial over geologic time, eventually produce oil as they are cooked in the "petroleum kitchen" (AKA hydrocarbon kitchen, oil kitchen: yes, they really do use that term in the oil business). A solid refractory high-carbon-content residue usually remains.

You may wonder, why we just don't industrially fry up algae to produce oil? There has actually been research into that, both fossil algae and fresh algae. Thirty-to-forty years ago, after the 1973 Arab Oil Embargo, there was a peak of research and pilot plants, in the United States, for producing liquid fuels from Western US oil shale, a rock rich in algal kerogen. The research looked at the feasibility of heating oil shale to produce and extract oil that had not yet been geologically cooked out of the fossil algae. The Green River Shale in Wyoming, Utah, Colorado, was a prime target rock. A positive outcome of this research was improved understanding of the chemical reaction kinetics of petroleum generation; kinetic algorithms by Lawrence Livermore National Lab scientists are the standard today in petroleum generation modeling. A major environmental, and political, issue, however, is that some methods can require a lot of water, which would monopolize excessive amounts of upstream Colorado River water to the detriment of downstream agricultural and drinking water customers in the SW US and Mexico.

Considering that farming algae on a large scale would be a possible transportation biofuels source, ExxonMobil, in 2009, supported ongoing research on growing algae on a large (numbers) scale and then extracting the lipids. (http://www.bloomberg.com/news/2013-05-21/exxon-refocusing-algae-biofuels-program-after-100-million-spend.html; now in 2021, regrettably behind a subscriber pay wall).  Advantages of the algae-farm technique is that it is renewable on the short term, may consume carbon dioxide, and does not include mining or mine waste disposal, like the Synfuels oil shale project would. However, as the Bloomberg article says, existing strains of algae were found not to produce an economically viable amount of product. Research by Exxon's partner will now focus on potential genetic modifications that may in a couple decades be successful. The business reports bemoan the project as a failure since $100 million (out of the original $600 million budgeted) has been spent without success. But actually . . . it is a success of the scientific method! There was a hypothesis, experiments were designed to test it. Even though the hypothesis was not proven true, there is valuable knowledge gained, and a new path proposed. It did cost money, but scientific inquiry does cost money, and advancement of basic science and technology can not happen without it.

It's winter! Marine snow?

Six feet in 24 hours: that was the unfortunate high rate of snowfall in Buffalo, New York, on the shore of Lake Erie on Tuesday, 11/18/2014. Even for a region used to very snowy winters, that was excessive and paralyzing.

Six meters in a million years. That is the accumulation rate for "marine snow". Marine snow, according to the National Oceanic and Atmospheric Administration (NOAA) informational webpage on the subject (http://oceanservice.noaa.gov/facts/marinesnow.html), is the shower of organic matter falling from upper marine waters to the ocean bottom. The "snow" consists of fluffy agglomerations of generally structureless decaying organic matter, the microbes feasting on it, clay particles, dust, tiny plankton shell pieces. The "flakes" may get to several centimeters. The organic matter may be consumed or depleted before it settles on the bottom, or may accumulate and be a food source at the seafloor. The NOAA page says that 3/4 of the seafloor may be covered with an accumulated organic ooze from marine snow deposition.

One-centimeter aquatic snow aggregate, Lake Constance, Germany.

For photo credit, see http://www.sciencedaily.com/releases/2010/12/101208125759.htm 

Microbes consume organic matter in marine snow and release carbon dioxide, so the velocity of settling affects exposure time and has a direct impact on the amount of CO2 released back to the ocean. The amount and type of particulates in the snow affect the density of a clump and its settling rate. In Proceedings of the National Academy of Sciences in 2010, Kindler and others (http://www.sciencedaily.com/releases/2010/12/101208125759.htm) conclude that the highly porous marine snow (~95% water) may stall during their journey to the bottom when increasing water density halts settling. When diffusion eventually replaces the less dense water from shallower depths within the flakes with denser water, the agglomerations resume their journey to the bottom.

Besides its importance in the ocean carbon cycle, the amorphous organic matter (AOM) in marine snow is a great petroleum precursor. If preserved, due to low or zero oxygen in ocean floor sediments or overlying waters, and buried to a few km or more, the AOM will start producing liquid hydrocarbons. A good description of amorphous organic matter and various formation pathways, modern and ancient, is found in the 1995 text "Sedimentary Organic Matter" by R. V. Tyson. Pacton and others (2011; http://www.climategeology.ethz.ch/publications/2011a_Pacton_et_al.pdf) describe the structures and process of formation of amorphous organic matter at the sediment/water interface.