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3 minute read
Cassini explores the depths of a methane sea on Titan
A pioneering oceanographic study of one of Saturn's moon's seas gives a clearer picture of its composition and topography. Bill Condie reports.
(more at link: https://cosmosmagazine.com/space/cassin ... -sea-titan )
Ligeia Mare is about the same size as Lake Huron and Lake Michigan combined.
"Before Cassini, we expected to find that Ligeia Mare would be mostly made up of ethane, which is produced in abundance in the atmosphere when sunlight breaks methane molecules apart," says Le Gall.
"Instead, this sea is predominantly made of pure methane."
Her study is based on data collected with Cassini's radar instrument during flybys of Titan between 2007 and 2015 and combines several radar observations of heat given off by the sea as well as data from a 2013 experiment that bounced radio signals off it.
That 2013 experiment sent back echoes from the seafloor giving an indication of the sea's depth – 160 metres at its deepest point.
Le Gall and her colleagues used the data to get an idea of what the composition of the sea and the seabed might be.
"We found that the seabed of Ligeia Mare is likely covered by a sludge layer of organic-rich compounds," she says.
How different organic compounds make their way to the seas and lakes on Titan, the largest moon of Saturn – ESA
This tallies with what we previously knew about the moon. Nitrogen and methane react in the atmosphere to produce a wide variety of organic materials, the heaviest of which are believed to fall to the surface.
Le Gall's study suggests that when these compounds reach the sea some are dissolved in the liquid methane while the insoluble ones, such as nitriles and benzene, sink to the sea floor.
The study found that the shoreline around Ligeia Mare may be porous and sodden with liquid hydrocarbons. The scientists deduced that by measuring temperature changes between spring and summer. Unlike on Earth, they recorded little change between the temperature of the land and the sea, suggesting that the land is so filled with hydrocarbons, it changes temperature at much the same rate.
"It's a marvellous feat of exploration that we're doing extraterrestrial oceanography on an alien moon," said Steve Wall, deputy lead of the Cassini radar team at NASA's Jet Propulsion Laboratory in California.
"Titan just won't stop surprising us."
https://cosmosmagazine.com/space/cassin ... -sea-titan
Liquid methane and ethane flowing through Vid Flumina, a 400-kilometre river often compared to the Nile River, is fed by canyon channels running hundreds of metres deep.
ut during this pass, the radar was used as an altimeter, sending pings of radio waves to the moon's surface to measure the height its features.
The timing of the radar echoes bouncing off the canyons' edges and floors gave the Cassini team a direct measure of their depths.
The researchers combined the altimetry data with previous radar images of the region to make their discovery and proposed scenarios for the deep cuts, such as terrain uplift and changes in sea level – or perhaps both.
"It's likely that a combination of these forces contributed to the formation of the deep canyons, but at present it's not clear to what degree each was involved," says Valerio Poggiali of the University of Rome and lead author of the study.
https://cosmosmagazine.com/space/titan- ... ed-canyons
- The Great Dog
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https://www.thunderbolts.info/wp/2018/0 ... -on-titan/
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This political commentator on YouTube has a new video today discussing oil production. Here's the link.
USA Now the Worlds Largest Oil Producer
The reason I'm posting it here is because he accepts the claim that oil is abiotic in origin, which means that it is produced within the Earth and is thus replenished over time, though not as fast as it's being extracted. He only discusses that briefly toward the end. But it's interesting anyway that the U.S. is apparently now the top producer of oil and maybe natural gas and coal too.
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Before It's News
Mon, 13 Feb 2017 22:29 UTC
New research published in Earth and Planetary Science Letters describes how scientists have used the world's largest array of seismic sensors to map a deep-Earth area of melting carbon covering 1.8 million square kilometers. Situated under the Western US, 350km beneath the Earth's surface, the discovered melting region challenges accepted understanding of how much carbon the Earth contains - much more than previously understood.
The study, conducted by geologist at Royal Holloway, University of London's Department of Earth Sciences used a huge network of 583 seismic sensors that measure the Earth's vibrations, to create a picture of the area's deep sub surface. Known as the upper mantle, this section of the Earth's interior is recognized by its high temperatures where solid carbonates melt, creating very particular seismic patterns.
"It would be impossible for us to drill far enough down to physically 'see' the Earth's mantle, so using this massive group of sensors we have to paint a picture of it using mathematical equations to interpret what is beneath us," said Dr Sash Hier-Majumder of Royal Holloway.
He continued, "Under the western US is a huge underground partially-molten reservoir of liquid carbonate. It is a result of one of the tectonic plates of the Pacific Ocean forced underneath the western USA, undergoing partial melting thanks to gasses like CO2 and H2O contained in the minerals dissolved in it."
As a result of this study, scientists now understand the amount of CO2 in the Earth's upper mantle may be up to 100 trillion metric tons. In comparison, the US Environmental Protection Agency estimates the global carbon emission in 2011 was nearly 10 billion metric tons - a tiny amount in comparison. The deep carbon reservoir discovered by Dr. Hier-Majumder will eventually make its way to the surface through volcanic eruptions, and contribute to climate change albeit very slowly.
Contacts and sources:
Royal Holloway, University of London
Citation: Pervasive upper mantle melting beneath the western US. Authors: Saswata Hier-Majumdera, Benoit Tauzinb. Earth and Planetary Science Letters Volume 463, 1 April 2017, Pages 25 - 35
(More at link: https://www.sciencedirect.com/science/a ... X16307543/ )
https://www.sciencedaily.com/releases/2 ... 090756.htm
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Anna Neubeck,corresponding author1 Nguyen Thanh Duc,1 David Bastviken,2 Patrick Crill,1 and Nils G Holm1
Author information Article notes Copyright and License information Disclaimer
This article has been cited by other articles in PMC.
Hydrocarbons such as CH4 are known to be formed through the Fischer-Tropsch or Sabatier type reactions in hydrothermal systems usually at temperatures above 100°C. Weathering of olivine is sometimes suggested to account for abiotic formation of CH4 through its redox lowering and water splitting properties. Knowledge about the CH4 and H2 formation processes at low temperatures is important for the research about the origin and cause of early Earth and Martian CH4 and for CO2 sequestration. We have conducted a series of low temperature, long-term weathering experiments in which we have tested the CH4 and H2 formation potential of forsteritic olivine.
The results show low temperature CH4 production that is probably influenced by chromite and magnetite as catalysts. Extensive analyses of a potential CH4 source trapped in the crystal structure of the olivine showed no signs of incorporated CH4. Also, the available sources of organic carbon were not enough to support the total amount of CH4 detected in our experiments. There was also a linear relationship between silica release into solution and the net CH4 accumulation into the incubation bottle headspaces suggesting that CH4 formation under these conditions could be a qualitative indicator of olivine dissolution.
It is likely that minerals such as magnetite, chromite and other metal-rich minerals found on the olivine surface catalyze the formation of CH4, because of the low temperature of the system. This may expand the range of environments plausible for abiotic CH4 formation both on Earth and on other terrestrial bodies.
The CH4 detected in the Martian atmosphere [1-3] in 2004 raised the question whether or not the CH4 were formed biotically or abiotically. It was suggested by Krasnopolsky et al.  that microorganisms on Mars may have produced it. However, several abiotic processes may be responsible for the detected atmospheric CH4, such as volcanism, exogenous sources and serpentinization of ultramafic rocks [4-6]. There are too few hot spots present on Mars to account for the CH4 concentrations that were detected and volcanism is not likely to be the major source of CH4 on Mars. Neither are the exogenous sources, such as meteorites and comets, for the same reason. Oze and Sharma  have calculated reaction rates for olivine dissolution on Mars, using olivine chemical compositions found in the Martian Schergottite-Nakhlite-Chassigny (SNC) meteorites, a temperature of 25°C and varying pH. They came to the conclusion that dissolution of olivine is favorable in the subsurface of Mars at such low temperatures, both kinetically and thermodynamically, which means that serpentinization would be a potential source for CH4 detected on the Martian atmosphere.
On the contemporary Earth, there are also CH4 seeps and plumes that are suggested to be of abiotic origin, at least to some extent [7-9]. Abiotically formed CH4 may provide carbon and energy for microorganisms in the deep subsurface biosphere and may serve as a precursor for forming longer hydrocarbons such as natural gas and oil. This process may be important for CO2 sequestration. Basaltic (45-52% SiO2) and ultramafic (<45% SiO2) hydrothermal systems as well as continental groundwaters host a vast number of bacterial and archaeal organisms [10,11] found at depths down to at least 800 meters below the seafloor (mbsf)  and in volcanic glass at depths down to 954 mbsf . Microbial communities are also found in volcanic hot springs, in saline groundwaters at depths exceeding 2 km in igneous rocks, and in continental flood basalts . Some microorganisms living in these environments are chemolithoautothrophs, i.e., they are autotrophic organisms that derive their energy from inorganic compounds such as H2 and CH4 emanating from rock-associated fluids and gases. An important question is to what extent microorganisms can use the chemical energy released exclusively from the alteration of olivine, one of the most common mineral in the Earth mantle [14-19]. This question bears upon the dynamics of contemporary subsurface microbial communities and the possibilities for such extreme environments to be modern analogues to early Earth ecosystems.
FTT reactions are considered to be common in hydrothermal systems and ultramafic rocks and have also been the focus for research considering the abiotic formation of precursors of biologically critical molecules such as amino acids and lipids [7,8,17,25].
Berndt et al.  conducted olivine dissolution experiments based on the study of Janecky and Seyfried . They wanted to explicitly study the CH4 forming processes coupled to olivine dissolution and serpentinization at 300°C and 500 bars. They could see a distinct increase in CH4 throughout the experiments and also an increase in other hydrocarbons such as C2H6 and C3H8. The catalyst present in their experiment was exclusively magnetite. Later, Horita et al.  confirmed the formation of CH4 through serpentinization, but also showed that magnetite is not the only and most efficient catalyst to form CH4 in an olivine dissolution environment. Instead, the presence of awaruite (Ni3Fe) increased the rate of formation severalfold. Since awaruite is a common associated mineral in ultramafic rocks , this approach was highly relevant. Another experiment made by McCollom et al.  with the purpose of investigating the formation of hydrocarbons through serpentinization of olivines and with no additional catalysts, showed continuous increase of CH4 throughout the experiment. The experiments were conducted under a pressure of 350 bars and 300°C. However, most of the CH4 (about 80%) found in these experiments was most likely not formed but was suggested to be released from fluid inclusions and carbon species within the olivine crystals. Another interesting observation in their experiments, though, was the need of fresh mineral surfaces in order to form CH4 which was probably due to partial oxidation of the surface. Instead of Ni-bearing catalysts, Foustoukos and Seyfried  used a mixture of Cr and Fe oxides (chromite, FeCr2O4) in an effort to produce hydrocarbons under hydrothermal conditions (390°C and 400 bars). Chromite is commonly associated with olivine-rich rocks and would therefore be part of a natural ultramafic hydrothermal system. The found CH4 concentrations were higher than earlier experimental efforts without the presence of Cr,Fe-bearing catalysts. It is now widely accepted that CH4 may be produced abiotically though serpentinization reactions at temperatures around 300°C. Previous studies regarding the FTT or Sabatier reactions often considered temperatures over 100°C. High temperatures promote faster reaction rates and lower kinetic barriers but are not suitable for living cells and can only support chemosynthetic life at a distance along a diffusion and temperature gradient within a hydrothermal environment, such as the porous lava layers or the diffuse vents in which hot hydrothermal water is mixed and quenched by downwelling seawater. However, if significant H2 formation with additional, indirect formation of reduced compounds occurs at lower temperatures, it would drastically expand the potential environments where such reactions can support microbial life. Studies of olivine alteration at lower temperatures are essential regardless of slower reaction rates and the need of long-term studies. In this study we focus on serpentinization in the temperature range of 30 to 70°C and whether significant formation of H2 and CH4 can be measured at such temperatures.
More at link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3157414/
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Proc Natl Acad Sci U S A. 2019 Sep 3;116(36):17666-17672. doi: 10.1073/pnas.1907871116. Epub
2019 Aug 19.
Abiotic methane synthesis and serpentinization in olivine-hosted fluid inclusions.
Klein F1, Grozeva NG2, Seewald JS3.
1 Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA 02543; firstname.lastname@example.org.
2 Massachusetts Institute of Technology-Woods Hole Oceanographic Institution Joint Program in Oceanography, Cambridge, MA 02139.
3 Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA 02543.
The conditions of methane (CH4) formation in olivine-hosted secondary fluid inclusions and their prevalence in peridotite and gabbroic rocks from a wide range of geological settings were assessed using confocal Raman spectroscopy, optical and scanning electron microscopy, electron microprobe analysis, and thermodynamic modeling. Detailed examination of 160 samples from ultraslow- to fast-spreading midocean ridges, subduction zones, and ophiolites revealed that hydrogen (H2) and CH4 formation linked to serpentinization within olivine-hosted secondary fluid inclusions is a widespread process. Fluid inclusion contents are dominated by serpentine, brucite, and magnetite, as well as CH4(g) and H2(g) in varying proportions, consistent with serpentinization under strongly reducing, closed-system conditions. Thermodynamic constraints indicate that aqueous fluids entering the upper mantle or lower oceanic crust are trapped in olivine as secondary fluid inclusions at temperatures higher than ∼400 °C. When temperatures decrease below ∼340 °C, serpentinization of olivine lining the walls of the fluid inclusions leads to a near-quantitative consumption of trapped liquid H2O. The generation of molecular H2 through precipitation of Fe(III)-rich daughter minerals results in conditions that are conducive to the reduction of inorganic carbon and the formation of CH4 Once formed, CH4(g) and H2(g) can be stored over geological timescales until extracted by dissolution or fracturing of the olivine host. Fluid inclusions represent a widespread and significant source of abiotic CH4 and H2 in submarine and subaerial vent systems on Earth, and possibly elsewhere in the solar system.
More at link with subscription: https://www.ncbi.nlm.nih.gov/pubmed/31427518
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Interesting overall read, Eugene. Bacteria is quite the impressive life form. I wasn't aware that living bacteria was found on the space station. Either way, I've long thought that a deep biosphere was the cause of our hydrocarbons, and not a pile of dead dinosaurs.paladin17 wrote:Incidentally, in my recent paper I've mentioned that a hypothetical ultra-deep biosphere might be the source of hydrocarbons - see Section 5.2.
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Could you highlight the major breakthroughs across deep carbon research in the past ten years?
Deep carbon science has produced transformative discoveries in a range of fields over the past decade. We now understand much better where in Earth carbon is stored, and in what forms. The iron-rich core, for example, may hold more than two-thirds of the total carbon in Earth in the form of iron carbide species. ...
... The deep biosphere has been studied in greater detail than ever before; we now know that the biomass subsisting, in slow motion over millennia—cells gleaning energy from rocks in the subsurface sediments and crust down to a few kilometer depth—amounts to more than 250 times the mass of all humans on Earth. ... Some of the most astonishing breakthroughs have come from the study of seafloor rocks and fluids. For example, the discovery of amino acids and complex organic compounds in oceanic crust sheds light on the origin of life on Earth through processes linked to “serpentinization”—alteration of seafloor volcanic rocks—and the associated formation of abiotic methane and higher hydrocarbons. ...
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https://www.upi.com/Science_News/2019/1 ... 571414891/
Having briefly conversed with Thomas Gold on this subject some 20 years ago, I'm sure he would not have been surprised by the latest findings.
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