This "methane-based life" is highly speculative, to say the least.redeye wrote:I've long considered Titan to be the best candidate for life in our Solar System (probably cos I read it somewhere).
In light of observations this speculation seems to be unfounded.There is also speculation as to the presence of liquids on it's surface which could provide an emulsion which is considered necessary for life.
Don't let your hopes and expectations cloud your judgment, this story seems like rubbish to me.It's quite speculative but I've been waiting ten years for news like this.
I don't recall anyone anticipating organisms that use arsenic instead of phosphorous for its metabolic processes, so the list of people who can laugh about it must be exceedingly short. It's worth noting that these organisms are closely related to nearly identical organisms that use phosphorous. It's also worth noting that this evolutionary cul-de-sac only exists in certain "extreme" environments where the phosphorous-using ogranisms can colonize and adapt through reproduction. These environments have arsenic available but not phosphorous. This is a case of organisms "just getting by" in extremely hostile environments and doesn't represent some new "branch" of life. If you stress similar organisms in an anoxic environment they will gobble up available phosphorous. If you give these organisms phosphorous instead of arsenic, they will start using it.HelloNiceToMeetYou wrote:Thats what they said about arsenic. Now look whos laughing
Also there is this:
https://www.washingtonpost.com/wp-dyn/c ... 04183.html
NASA held a press conference Thursday afternoon in which they revealed the discovery of arsenic-based life forms on Earth.
http://online.wsj.com/article/SB1000142 ... logsModule
Researchers on Thursday said they had bred microbes that absorb the notorious poison arsenic into their DNA, in an experiment that could rewrite the rules of life.
So which is it? Was this organism discovered or created in a lab?
Their finding comes as the hunt for Earth-like planets accelerates.
This stinks like a PR stunt to me, along the lines of the "bacteria discovered" in a rock from Mars. I wish people weren't so gullible.
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What if the residents resembled plants more than animals? In that they required not much more than some form of EM radiation and the gases in the air around them to perform something similar to photosynthesis? (Or some kind of chemosynthesis?). Or some completely alien and unexpected system of obtaining energy? Biological life on any other planet doesn't have to conform to any of our expectations. After all, Earth's home to a number of different kingdoms of life (plants, animals, fungi etc.) that have biological systems that are completely alien to each other. A biologist who has studied nothing but animals and never come across a plant in his life, would struggle to understand how a plant can be a living being and could stare straight at a planet full of trees without recognising any life at all. I suspect the same thing will happen to us.jjohnson wrote:
I'm no ethnobiologist and a lousy chemist, but how do you conduct redox reactions for energy where the elements being considered are all what we consider "fuels"? Is acetylene an oxidizer? In our metabolism, energy comes from oxidizing reactions with our carbon-based food and cell contents. We breathe in our "oxidizer" - literally, oxygen molecules in air - but what would a Titan resident breathe or aspirate or absorb to do the same? Not the hydrogen, which is an electron donor, not an electron "receiver" like fluorine or oxygen, etc. This will be interesting to follow and see if it gets any traction.
-- Walter Russell
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http://blogs.physicstoday.org/thedaysid ... ctors.htmlPhosphorus is the ninth most abundant element in living organisms. Its compounds are found in teeth, bones, cell membranes, and a host of important biomolecules, including cells' main source of chemical fuel, adenosine triphosphate. Phosphate groups also hold together the nucleotides in RNA and DNA.
Because arsenic belongs to the same group in the periodic table as phosphorus, it can readily replace phosphorus in biomolecules. But the arsenated compounds don't work—hence the element's toxicity. The newly discovered bacteria are remarkable in that they apparently possess a chemical means of mitigating the toxicity.
But before you start scanning the skies for arsenic-laced M-class planets, keep in mind that arsenic is cosmically rarer than its group V neighbor phosphorus. In Earth's crust arsenic occurs at a concentration of about 1.5 parts per million. Phosphorus is 1000 times more abundant.
Life as we know it on Earth originated just once, a reflection of its low probability of getting started. I'm therefore skeptical that life forms based on a rare element such as arsenic evolved elsewhere.
I can't resist ending this blog entry by pointing out another scientific substitution of arsenic for phosphorus. Three years ago in his quest to find semiconductors with interesting magnetic properties, Hideo Hosono and his team from the Tokyo Institute of Technology synthesized a compound with the chemical formula LaOFeP.
The material becomes superconducting at the unremarkably low temperature of 4 K. But the arsenic-substituted compound, when doped with fluorine, superconducts at 26 K, which is uncomfortably high for a normal superconductor. Hosono had discovered a new and exciting class of superconductor.
Despite spawning thousands of papers from excited physicists and chemists around the world, Hosono's discovery barely registered in the mainstream media.
Also from this blog:seasmith wrote:http://blogs.physicstoday.org/thedaysid ... ctors.html
"Now, Felisa Wolfe-Simon and colleagues have found a bacterium able to completely swap arsenic for phosphorus to the extent that it can even incorporate arsenic into its DNA. The salt-loving bacteria, a member Halomonadaceae family of proteobacteria, came from the toxic and briny Mono Lake in California. In the lab, the researchers grew the bacteria in Petri dishes in which phosphate salt was gradually replaced by arsenic, until the bacteria could grow without needing phosphate, an essential building block for various macromolecules present in all cells, including nucleic acids, lipids and proteins. Using radio-tracers, the team closely followed the path of arsenic in the bacteria; from the chemical’s uptake to its incorporation into various cellular components. Arsenic had completely replaced phosphate in the molecules of the bacteria, right down its DNA."
In light of this revelation, I find it very disingenuous (or ignorant, or both) that so many media outlets announced this as the "discovery of an arsenic-based organism". They discovered an organism that could TOLERATE arsenic, then gradually leached all the phosphorous out of them over successive generations of reproduction. This discovery has nothing to do with exobiology, it's probably just a stepping stone to developing organisms that voraciously gobble up arsenic, why, I have no idea, use your imagination.
And honestly, what does arsenic have to do with Titan, anyway.
Here's a blurb from two days ago:
"NASA's announcement today at its Washington headquarters is widely anticipated, as talk abounds that an arsenic-based life form was discovered on Titan's, Saturn's moon. Astrobiology will be at the center of the discussion led by an expert panel of some of the brightest minds in their respective fields. The NASA announcement, scheduled for 2 p.m. has many wondering if alien life forms have in fact been discovered."
This "news" was posted before the announcement of the "discovery" of the invented organisms, and is liberally laced with speculations about life on Titan. Why was this done? Is it common for press releases to be given about upcoming press releases? It looks as if it was done just to cause this kind of speculation. NASA has seized on this organism and is using as it the explanation for further exploration of Titan. Is there a lot of arsenic on Titan I haven't heard about? What the hell is going on.
Reason: Amended title to reflect the thread and remove unnecessary offensiveness - DS.
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I surmise that hydrogen 'disappears' into Earth by bonding with oxygen that is created by our biosphere and accounts for the abundant water we have on this world. What element exists on Titan that could bind with hydrogen? Doesn't it make more sense to bear in mind that the hydrogen that is arriving at the Titan atmosphere is ionized (just as it is on Earth and everywhere else in the solar system), and therefore we should be looking for a chemical bonding mechanism to accound for the hydrogen disappearance?
It seems to me that everyone is jumping on a roller coaster of speculation here based upon what they want to see, rather than opening themselves up to less speculative possibilities.
"I have no fear to shout out my ignorance and let the Wise correct me, for every instance of such narrows the gulf between them and me." -- Michael A. Harrington
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On Earth it has to be created, using an arc jet or in a petrochemical refinery, typically. As a fuel, it does well when combined with oxygen in a welding torch. I cannot guess a plausible reason why acetylene might be disappearing on Titan, but then, I can't guess what process on Titan would create acetylene in the first place. Maybe the "river valleys" really are Lichtenberg figures from electric discharges, which might provide the energy for chemical processe that could result in a variety of hydrocarbon compounds, including acetylene.
The scientists had earlier predicted that sunlight on Titan's upper atmosphere could be creating acetylene, but I have not read how much acetylene, if any, has been verified spectroscopically in the atmosphere by the Cassini spacecraft.
If the UV light level is high enough at Titan, it could ionize hydrogen molecules which in turn might react with other carbon compounds to create acetylene, but does it? I don't know, so I'm stumped even before the loss of hydrogen question (from the supposed acetylene) comes up.
Titan is cold. Natural chemical reactions at the surface would proceed rather more slowly, I'm thinking, without help. Being in the vicinity of the Jovian electrodynamic environment might be able to speed things up a bit. We do not really know enough about life and how readily it forms in environments outside ours, however extreme or benign they might appear to us. Tube worms living in the dark around "black smoker" seawater vents, living on sulfur dissolved in water at high pressure and temperature, wouldn't have been anybody's first guess at a viable form of life on our planet at mid-20th century. Until we can go toTitan and see for ourselves, it's a crapshoot and we just have to realize that it's speculative and hypothetical. Nothing wrong with that - the idea factory isn't supposed to run dry, but it does get sharpened up a bit when you can look at it in your gloves, and poke it and smell it.
I thought that the story on the bacteria from Mono Lake was intriguing, and it is relevant to any story about life and its possibility in other, unfamiliar environments, including this discussion of Titan's chemistry. I enjoyed the NPR interview with the lady scientist who handled the investigation, and the "Through The Wormhole" story narrated by Morgan Freeman which included that story as part of a larger story on "how did life get started on Earth?" Those writers sure trotted that one out fast!
I disagree with Grits's observation that it "This stinks like a PR stunt to me..." other than any press release and interview could be construed as a "stunt" to keep people informed and interested in what sorts of things science and scientists are doing with their money. Let's use common sense and tone down the phrases like "foolish media whores", if you please. That's not productive in any adult sort of way. I find the adaptability of a bacterium living in what to us would be an extremely toxic environment, by counteracting the usual toxic effects by modifying and adapting its body chemistry, to be a good sign that life is unlikely to be restricted to planets with about 1 gee and near the triple point of water and with an oxygen and carbon cycle in (our) Goldilocks Zone.
I think your idea, Aveo9, that if cellular life were found on Titan, it might be more plant-like, to have a lot of merit. If high-energy-density redox chemistry is not prevalent, what could successfully operate at a glacial pace in a low energy environment? Stuff like algae and mushrooms. A water-based chemistry on a frozen planet isn't much of a starter, so however life adapted, it would have to go with an energy balance that would let it flourish in a different environment than ours. How would things evolve to include predation, or would they? Predation is a shortcut to obtain already-gathered and processed energy in concentrated and usable form, so it's sort of a natural branch? path? of evolution. Plant on plant predation is not uncommon here. It might work on Titan, too! First, though, let there be plants!
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* EU would probably say that those hydrocarbon grains of sand probably do not precipitate out of Titan's methane-containing atmosphere, but is detritus from Saturn flares, maybe 10,000 years ago. Does anyone know which hydrocarbons these sands are made of? I suspect petroleum or tar, but why would the grains be millimeter size? Could the grains be charcoal?... [S]and on (Saturn's moon) Titan is not made of silicates as on Earth, but of solid hydrocarbons that precipitate out of the atmosphere. These then aggregate into millimetre-sized grains by a still unknown process.
... Though similar in shape to the linear dunes found on Earth in Namibia or the Arabian Peninsula, Titan's dunes are gigantic by our standards. They are on average 0.6 to 1.2 miles (1 to 2 kilometers) wide, hundreds of miles (kilometers) long and around 300 feet (100 meters) high. However, their size and spacing vary across the surface, betraying the environment in which they have formed and evolved.
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Somebody else might want to post this on one of the other sections of the forum, again I've had one too many posts pulled on the other sections to want to bother.
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* It would be interesting if Titan turns out to be fairly liquid, to account for its apparent periodic slight changing of shape. That would suggest that it hasn't cooled down completely yet after Saturn's last flare 10,000 years ago, when the Saturn system apparently entered the Solar System.
* Here's a good video of the view from the probe that settled on Saturn in 2005: http://www.youtube.com/watch?v=sLfiRI7ZuGU. It seems to descend over hilly, rocky terrain. Toward the end, however, when it lands, there are said to be rock-like objects that are actually water ice and possibly pebbles of methane or hydrocarbons. The view seems to blur a bit soon after the landing, which is said to be due to heat from the landing vaporizing some of the methane or hydrocarbons.
* Anyway, it seems to confirm that there is water and or hydrocarbons on Titan. The shadow of the parachute is also seen after the landing. It looks like the camera only faced one direction upon landing. It would have been nice to have a wider angle view. But it's still rather good.
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This comparison image used in the article is quite interesting (if the image is cropped on one side, Right-Click it and select 'View Image' from the drop down menu to see it in its entirity).Radar images from NASA's Cassini spacecraft reveal some new curiosities on the surface of Saturn's mysterious moon Titan, including a nearly circular feature that resembles a giant hot cross bun and shorelines of ancient seas...
..."The 'hot cross bun' is a type of feature we have not seen before on Titan, showing that Titan keeps surprising us even after eight years of observations from Cassini," said Rosaly Lopes, a Cassini radar team scientist based at NASA's Jet Propulsion Laboratory, Pasadena, Calif...
Geological processes are used to explain the similarities. I'm thinking that electical discharges are responsible for the nearly identical pattern.
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