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article imageLife may exist on Titan, but not like anything we know

By Stephen Morgan     Feb 28, 2015 in Science
A team of scientists from Cornell University believe that oxygen-free, methane-based life forms could exist on Titan. Such life forms would be unlike anything we know on Earth and live in conditions, which nothing in our biosphere could endure.
It seems too much of a coincidence that during the week that Leonard Nimoy passed away, Spock's immortal quote, "Its life Jim, but not as we know it," should possibly come true on Titan.
So are we, like the crew of Star Trek Enterprise, to encounter new life forms, such as we could never have imagined? Researchers at Cornell certainly seem to think so.
However, you shouldn't worry that Klingons are amassing their forces on Saturn's moon to invade Earth. And you can forget about learning Romulan for career enhancement, what the scientists are talking about here is organic compounds and membranes, the basic forms of life.
Even so, if it were found to be true that life could exist in the most unearth-like and unexpected environments, this would be a game changer in the hunt for alien life. Indeed, who is to say that intelligent beings couldn't evolve in methane, helium or hydrogen atmospheres and in conditions both poisonous and unbearable for humans?
As Sci-News points out,
"many scientists seek alien life in what’s called the circumstellar habitable zone, the narrow band around the Sun in which liquid water can exist." This would have to change if the researchers at Cornell University are correct.
So what would a Titan lifestyle look like? Well it does have seas, but they are not made of water, they are composed of liquid methane instead. There isn't any oxygen either, even though its atmosphere is rich in nitrogen like Earth.
It would be in the seas that some form of life might exist, but we would have to look for cells which thrive on methane not water, which luckily has a far lower freezing point than water, because the temperature on Titan is 93.7 K (−179.5 °C or -291.°F)
Now, a combination of chemical engineers and astronomers have come up with what might be a working model of how life on Titan exists in an oxygen-free, methane environment.
Phys.org explains,
"On Earth, life is based on the phospholipid bilayer membrane, the strong, permeable, water-based vesicle that houses the organic matter of every cell. A vesicle made from such a membrane is called a liposome."
However, Science Daily reports that for Titan's conditions, the researchers theorized a "cell membrane, composed of small organic nitrogen compounds and capable of functioning in liquid methane temperatures of 292 degrees below zero."
The name they have given to this cell is an "azotosome," made up from "azote," the French word for nitrogen. "Liposome" comes from the Greek "lipos" and "soma" to mean "lipid body;" and so by analogy, "azotosome" means "nitrogen body."
Their research showed that the azotosome can be made from nitrogen, carbon and hydrogen molecules, which exist in Titan's seas and which displays the same stability and flexibility that liposome does on Earth.
Tech Times quotes their results published last week in Science Advances, which said,
"Using molecular simulations, we demonstrate that these membranes in cryogenic solvent have an elasticity equal to that of lipid bilayers in water at room temperature."
Sci-news describes how they came to this discovery,
"They employed a molecular dynamics method that screened for candidate compounds from methane for self-assembly into membrane-like structures."
"The most promising compound they found is an azotosome based on acrylonitrile – a colorless, poisonous, liquid organic compound present in the atmosphere of Titan."
"The acrylonitrile azotosome showed good stability, a strong barrier to decomposition, and a flexibility similar to that of phospholipid membranes on Earth."
The research leaders are Paulette Clancy a chemical molecular dynamics expert and James Stevenson, a graduate student in chemical engineering, who authored the study's paper. The co-author is Jonathan Lunine, director for Cornell's Center for Radiophysics and Space Research, who is an expert on Saturn's moons and an interdisciplinary scientist on the Cassini-Huygens mission that discovered methane seas on Titan.
In order to further explore the possibility of life forms on Titan, Lunine approached experts in chemical modeling in Cornell. The engineers he cooperated with were more used to working with semiconductors rather than cells and membranes, but their unique involvement in researching astrobiology seems to have paid off.
"We're not biologists, and we're not astronomers, but we had the right tools," Paulette Clancy said. "Perhaps it helped, because we didn't come in with any preconceptions about what should be in a membrane and what shouldn't. We just worked with the compounds that we knew were there and asked, "If this was your palette, what can you make out of that?'
Stevenson has called it "the first concrete blueprint of life not as we know it." Clancy says the next step is to analyze azotosome's potential behavior with regard to reproduction and metabolism.
By modelling the way life might exist in such an alien environment, the researchers have provided scientists with a better place to start searching for it.
Lunine says he is looking forward to testing the theory on Titan itself, by "someday sending a probe to float on the seas of this amazing moon and directly sampling the organics."
More about Titan, Life, unlike, Earth, Exist
 
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