Beyond Nature

I have written about the Extraterrestrial and the Alien Mania stuff here in my previous posts. Now this post is all about life beyond Planet Earth! Man has always been in a constant search for a hospitable place in our solar system and studies reveal that his long cherished dream of living off the earth may come true one day! Europa and Titan--The two moons may be the next destinations of mankind! This post should have come up right after the science explorations but its just that I recently ran into a documentary on History Channel called "Histories Classroom" and that is how my curiosity grew regarding this topic! And hence here I am trying to bring about yet another interesting aspect of Beyond-Nature! Lets digg deeper...

It is the sixth of Jupiter's known satellites and the fourth largest; it is the second of the Galilean moons. Europa is slightly smaller than the Earth's Moon. It has fascinated the humans for hundreds of years now ever since it was discovered by Galileo in 17th century.

It has been suggested that life may exist in Europa's under-ice ocean, perhaps subsisting in an environment similar to Earth's deep-ocean hydrothermal vents or the Antarctic Lake Vostok. Life in such an ocean could possibly be similar to microbial life on Earth in the deep ocean. So far, there is no evidence that life exists on Europa, but the likely presence of liquid water has spurred calls to send a probe there.

Until the 1970s, life, at least as the concept is generally understood, was believed to be entirely dependent on energy from the Sun. Plants on Earth's surface capture energy from sunlight to photosynthesize sugars from carbon dioxide and water, releasing oxygen in the process, and are then eaten by oxygen-respiring animals, passing their energy up the food chain. Even life in the ocean depths, where sunlight cannot reach, was believed to obtain its nourishment either from consuming organic detritus rained down from the surface waters or from eating animals that did. A world's ability to support life was thought to depend on its access to sunlight. However, in 1977, during an exploratory dive to the Galapagos Rift in the deep-sea exploration submersible Alvin, scientists discovered colonies of giant tube worms, clams, crustaceans, mussels, and other assorted creatures clustered around undersea volcanic features known as black smokers. These creatures thrive despite having no access to sunlight, and it was soon discovered that they comprise an entirely independent food chain. Instead of plants, the basis for this food chain was a form of bacterium that derived its energy from oxidization of reactive chemicals, such as hydrogen or hydrogen sulfide, that bubbled up from the Earth's interior. This chemosynthesis revolutionized the study of biology by revealing that life need not be sun-dependent; it only requires water and an energy gradient in order to exist. It opened up a new avenue in astrobiology by massively expanding the number of possible extraterrestrial habitats. Europa's unlit interior is now considered to be the most likely location for extant extraterrestrial life in the Solar System.

While the tube worms and other multicellular eukaryotic organisms around these hydrothermal vents respire oxygen and thus are indirectly dependent on photosynthesis, anaerobic chemosynthetic bacteria and archaea that inhabit these ecosystems provide a possible model for life in Europa's ocean. The energy provided by tidal flexing drives active geological processes within Europa's interior, just as they do to a far more obvious degree on its sister moon Io. While Europa, like the Earth, may possess an internal energy source from radioactive decay, the energy generated by tidal flexing would be several orders of magnitude greater than any radiological source. However, such an energy source could never support an ecosystem as large and diverse as the photosynthesis-based ecosystem on Earth's surface. Life on Europa could exist clustered around hydrothermal vents on the ocean floor, or below the ocean floor, where endoliths are known to habitate on Earth. Alternatively, it could exist clinging to the lower surface of the moon's ice layer, much like algae and bacteria in Earth's polar regions, or float freely in Europa's ocean. However, if Europa's ocean were too cold, biological processes similar to those known on Earth could not take place. Similarly, if it were too salty, only extreme halophiles could survive in its environment.

In 2006, Robert Pappalardo, an assistant professor within the University of Colorado's space department, said, "We’ve spent quite a bit of time and effort trying to understand if Mars was once a habitable environment. Europa today, probably, is a habitable environment. We need to confirm this … but Europa, potentially, has all the ingredients for life … and not just four billion years ago … but today."

Regarding the info. about Ice-Surface, The Explorations and the History of this Moon we recommend you to visit the following sites..

Nine Planets

Solar Views

Europa-The Wiki Link



This brownish-yellow satellite might have appealed more to the TitanWorld-The Watch Manufacturers that they named their company after this moon . Known for its earth like atmosphere , rugged mountains and climatic features this satellite has been cited as a possible host for microbial extraterrestrial life or, at least, as a prebiotic environment rich in complex organic chemistry.

Scientists believe that the atmosphere of early Earth was similar in composition to the current atmosphere on Titan. Many hypotheses have developed that attempt to bridge the step from chemical to biological evolution. The Miller-Urey experiment and several following experiments have shown that with an atmosphere similar to that of Titan and the addition of UV radiation, complex molecules and polymer substances like tholins can be generated. The reaction starts with dissociation of nitrogen and methane, forming hydrocyan and ethyne. Further reactions have been studied extensively.
All of these experiments have led to the suggestion that enough organic material exists on Titan to start a chemical evolution analogous to what is thought to have started life on Earth. While the analogy assumes the presence of liquid water for longer periods than is currently observable, several theories suggest that liquid water from an impact could be preserved under a frozen isolation layer. It has also been observed that liquid ammonia oceans could exist deep below the surface; one model suggests an ammonia–water solution as much as 200 km deep beneath a water ice crust, conditions that, "while extreme by terrestrial standards, are such that life could indeed survive". Heat transfer between the interior and upper layers would be critical in sustaining any sub-surface oceanic life.

Detection of microbial life on Titan would depend on its biogenic effects. That the atmospheric methane and nitrogen are of biological origin has been examined, for example. Hydrogen has been cited as one molecule suitable to test for life on Titan: if methanogenic life is consuming atmospheric hydrogen in sufficient volume, it will have a measurable effect on the mixing ratio in the troposphere.

Despite these biological possibilities, there are formidable obstacles to life on Titan, and any analogy to Earth is inexact. At a vast distance from the Sun, Titan is frigid (a fact exacerbated by the anti-greenhouse effect of its cloud cover), and its atmosphere lacks CO₂. Given these difficulties, the topic of life on Titan may be best described as an experiment for examining theories on conditions necessary prior to flourishing life on Earth. While life itself may not exist, the prebiotic conditions of the Titanian environment, and the possible presence of organic chemistry, remain of great interest in understanding the early history of the terrestrial biosphere. Using Titan as a prebiotic experiment involves not only observation through spacecraft, but laboratory experiment, and chemical and photochemical modelling on Earth.

An alternate explanation for life's hypothetical existence on Titan has been proposed: if life were to be found on Titan, it would be statistically more likely to have originated from Earth than to have appeared independently, a process known as panspermia. It is theorized that large asteroid and cometary impacts on Earth's surface have caused hundreds of millions of fragments of microbe-laden rock to escape Earth's gravity. Calculations indicate that a number of these would encounter many of the bodies in the solar system, including Titan.

Conditions on Titan could become far more habitable in future. Six billion years from now, as the Sun becomes a red giant, surface temperatures could rise to ~200K, high enough for stable oceans of water/ammonia mixture to exist on the surface. As the Sun's ultraviolet output decreases, the haze in Titan's upper atmosphere will deplete, lessening the anti-greenhouse effect on the surface and enabling the greenhouse created by atmospheric methane to play a far greater role. These conditions together could create an environment agreeable to exotic forms of life, and will subsist for several hundred million years, long enough for at least primitive life to form.

Landing on the Moon Titan

While the Cassini–Huygens mission was not equipped to provide evidence for biology or complex organics, it did support the theory of an environment on Titan that is similar, in some ways, to that of the primordial Earth.

There are a wide range of options for future missions to Titan that might address these and other questions, including orbiters, landers, balloons etc.

Additional Info.

Solar Views

planetary.org - Explore the Cosmos

Titan-A world of Rivers and lakes on Space.com

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