Astrobiology is a discipline that explores the potential for life outside Earth. To find any life forms, ancient or present, outside Earth, will, essentially, support the idea that Universe is teeming with it. So far there has been no compelling evidence discovered for existence of extraterrestrial life. It is relatively new as a field; draws from Astronomy, Biology and Geology, as well as other disciplines to a lesser extent. Astrobiologists are studying evolution and diversity of life on Earth, in order to predict possibility of it elsewhere in the Universe. Extraterrestrial environments are examined for signs of life and their comparison to various conditions in Earth's past or present, that produced living organisms.
P.S. Most convincing non-astrobiological evidence of extraterrestrial life was received by the SETI Institute in 1977
The following is the most up to date list of planetary bodies where scientists theorize that life could exist
Enceladus: best chance for extraterrestrial life in the Solar System?
Active cryovolcanism on the southern pole. Click on the image to see it in full resolution.
Courtesy of NASA/nasaimages.org
Enceladus is moon of Saturn; it ranks very high in a list of known locations for potential presence of extraterrestrial life. It is a sixth largest moon of its parent planet, with a diameter of 500 kilometers (310 mi). Enceladus is one of only three known geologically active extraterrestrial bodies in the Solar System. In 2005 Cassini spacecraft studied the moon and revealed fascinating details. We now know that part of the surface is young, it has been recently tectonically deformed.
Cassini discovered that on the southern polar region, active cryovolcanism eruptions were spewing water vapor into space. Surface is now believed to be almost entirely made out of water ice. Saturn is, apparently, exerting gravitation influence, also known as orbital resonance that is cyclically heating up the moonís interior. Analysis of particles of ice by the Cassini spacecraft determined that it was salt water. Consequently, scientists arrived to a consensus that it is very likely that underneath the icy surface, a liquid salt water ocean is present. On Earth, salt water is found in oceans, as opposed to lakes or rivers. Liquid water is an academically accepted prerequisite for life, which makes Enceladus a potentially life harboring moon. Additionally, there is suggestive evidence of organic molecule presence, such as carbon, hydrogen, nitrogen and oxygen. Presence of liquid oceans means that there must be additional heat source within the moon, as Saturnís gravitational influence is not sufficient.
Hypothetical illustration. Click on the image to see it in full resolution.
Courtesy of NASA/nasaimages.org
Due to active cryovolcanism it will be relatively easy to conduct extensive studies on internal composition of Enceladus. Otherwise an exploration mission would have necessitated surface drilling which is significantly more complex and costly than a potential Enceladus-orbiting material-gathering and analyzing spacecraft mission would be. To surmise: Enceladus is warm, geologically active, has high chance of liquid salt water oceans being present under the surface and has chemical building blocks of life. Life may have evolved there, but it is yet to be discovered. If it did, what is it like?
Europa: enchanting and exceedingly promising
Europa is engulfed with mysterious ridges. Click on the image to see it in full resolution.
Courtesy of NASA/nasaimages.org
Europa is one of the moons of Jupiter. It is covered with an icy shell, covered with cracks, underneath which, as surface geology indicates, is a liquid ocean. Detailed images of the surface reveal unusual features, such as overlapping (cycloidal) ridges and overall poorly understood surface geology. It is theorized that the icy crust is rotating, as a whole, relative to the interior, as well as in relation one to another. This movement is possible due to liquid layer underneath the crust. Volume of Europaís ocean, some scientists postulate, exceeds that of all Earth oceans combined. Europaís heat source comes from Jupiterís gravitational influence: moon is cyclically contracted and expanded as its distance to Jupiter increases and decreases over time, generating internal heat. This gravitational flexing effect is exerted on all of Jupiterís moons.
Two possible scenarios of underwater geyser interaction. Click on the image to see it in full resolution.
Courtesy of NASA/nasaimages.org
Europa is orbiting within Jupiterís magnetic field and serves as a conductor, which leads to a strong suspicion that its subsurface oceans are salty in composition. Most scientists agree that with the amount of information in our possession, there is nothing indicating that life as we know it, in its microbial state, could not exist on Europa. If life did emerge there, it is likely that it did so around underwater geysers. Unfortunately, a mission to explore this possibility by NASA, named Jupiter Icy Moons Orbiter, which was designated to be launched in 2017, has been cancelled. It will, presumably, be resurrected in the 2020ís. It is possible that European Space Agency is going to join NASA on that historic journey.
Mars: no lush vegetation but there is still hope
False-color image of gully channels in a crater in the southern highlands of Mars, taken by the High Resolution Imaging Science Experiment (HiRISE) camera on the Mars Reconnaissance Orbiter. The gullies emanating from the rocky cliffs near the crater's rim (upper left) show meandering and braided patterns typical of water-carved channels.. Click on the image to see it in full resolution.
Credit: NASA/JPL/University of Arizona
The Red Planet is by far the most studied planetary body for the potential of extraterrestrial life. It is a planet of particular interest to us, because of its proximity to Earth and its similarities. Considering how hostile environments on all known worlds are, Mars is comparatively mild. Multiple NASA orbiting and landing missions had conclusively confirmed that Mars used to have liquid, flowing water on its surface, in its ancient past. Features of riverbeds, valleys, lakes and seas can be observed all over Martian surface. Today, however, the planet is almost entirely dry, there is still some possibility of liquid water existing below the surface.
Astrobiologists found extremophile bacterial organisms on Earth that could survive and thrive on Mars. This means that not only could there have been life in the past, but that it could still survive there, in a highly primitive form.
1976, Viking on Mars.
Credit: Courtesy of NASA/nasaimages.org
Click on the image to enlarge it
First successful landings on Mars were achieved by NASAís Viking program in 1976, which sent two scientific laboratories, designed to sample Martian surface material and detect life, if it was present. Results of those experiments are still disputed and some, in the scientific community, regard them to be inconclusive. However, the accepted consensus by high ranking officials is that no traces of life were detected.
ALH 84001 under high-resolution scanning electron microscope
Credit: Courtesy of NASA/nasaimages.org
Click on the image to enlarge it
In 1984 American scientists found a meteorite in Antarctica and named it ALH 84001. It appears to originate from Mars. Scientists postulate that it was blasted off of Martian surface 15 million years ago, a time when the Red Planet had liquid water. In 1996 NASA announced to the whole world that this meteorite possibly had fossilized traces of life. Whether what appears to be an extremely small bacteria (so-called nanobacteria) is a product of contamination of the meteorite after its arrival on Earth or was brought, following some sort of an impact, from Mars, cannot be established. This potential first evidence of extraterrestrial life remains to be inconclusive, adding to the mysterious allure of our brother planet.
Hope for life on Mars was resurrected in 2003, when NASA detected substantial amount of methane gas. It could only indicate that the planet is still active, either in geologic or biologic sense. Most of Earthís methane, for comparison, is released by living organisms. There are, however, geologic processes that could be responsible for presence of methane. If present, living organisms would need to be buried deep below, where its warmer and liquid water could still exist. On Earth some organisms survive several miles deep below the ground. Scientists had identified specific areas on Mars where methane is being released, which happen to also vary with seasons. These areas are now of upmost interest when considering future missions to the Red Planet. NASA rover Curiosity, however, which will land on Mars in 2012, will not examine these sights, it will, instead, focus on geological history of the planet, by examining the Gale crater.(1)
In August 2011, NASA announced an apparent discovery of a liquid flowing water on Mars, greatly increasing chances for presence of some kind of life on the Red Planet.
TITAN: liquid lakes 800 million miles away from Earth, but is there life?
Image courtesy of Ron Miller (c) 2010
Titan, to some, is the most fascinating planetary body in the Solar System, besides Earth. It is the largest moon of Saturn with a thick atmosphere and liquid rivers and lakes that exist right now, on its surface. Titan is too cold to support liquid water; instead liquid methane flows throughout, forming similar features as water does on Earth. Water, on the other hand, assumes the role of rocks on this bizarre world 800 million miles away from Earth.
It is a truly alien world; if you were to stand on its surface, you would see, through thick, green or orange fog, gigantic Saturn dominating the skies. Titanís equivalent of rain drops are likely to fall down very slowly. There are large, liquid lakes, identifiable shorelines and rivers. Humans cannot survive on it without protective equipment, at least not until transhumanism comes along with artificial upgrades. Nevertheless, American scientists are finding possible, circumstantial evidence, of biological processes.
Real image of Titan's surface taken by Huygens spacecraft. Click on the image to enlarge it.
Chemical analysis reveals that hydrogen molecules and acetylene hydrocarbons are absent from Titanís surface. This is important because it is contrary to expectations of scientists at NASA. Their absence suggests some sort of activity on the surface that consumes or transforms this element and chemical compound. One explanation is that potential methane-based life could feed on them. In fact, it is a likely energy source for this hypothetical life form. Evidence also indicates that organic compounds could be covering water ice (which serves as bedrock on Titan) beneath the surface. This layer of organic compounds should have been quickly washed off the water ice, had they not been continuously replenished. These theories are based on chemical analysis conducted by the Cassini spacecraft. (3)
The issue whether such exotic life form, different from our own, could exist, was a highly debated subject until American scientists at NASA announced a discovery in 2010 of a new life form; strain GFAJ-1 of the Halomonadaceae, found on Earth. Normally, life as we know it is based on the following elements: carbon, hydrogen, nitrogen, oxygen, sulfur, and phosphorus. New type of extremophile bacteria is able to substitute phosphorus with arsenic and thrive. Implications of this discovery for astrobiology can be discussed at length, but as far as Titan is concerned, this evidence postulates that diversity of types of life is higher than conservative estimates based on traditional life on Earth have been predicting, thus, hypothesized exotic alien life form on Titan could very well be real.(4)
Another, potential, concentration of primitive life forms could have developed around areas of cryovolcanism; water, mixed with other elements, is brought up from the interior, creating a possibly habitable environment for some extremophile bacteria.
Watch this special on Titan's Cryovolcanism from NASA in HD
Gliese 581 g (Zarmina)
First Earth-like exoplanet candidate, known to the Human race, is discovered
Comparison of Gliese 581 planetary system, its habitable zone with our Solar System
Click on the image to see it in full resolution.
Credit: ESO, Wikipedia (Henrykus)
Gliese 581 g (Zarmina) is unlike any other exoplanet (planet outside our Solar System) ever discovered. It is located in the middle of habitable zone of its parent star (Gliese 581, a Red Dwarf), like Earth. Which means that it is capable of sustaining liquid water on its surface due to mild temperatures. It has a mass approximately 3.1 to 4.5 that of Earth, which allows it to retain an atmosphere but not take in too much Hydrogen, which would turn it into a Gas Giant. The planet's radius is 1.3 to 2.0 that of Earth. It is appoximately 20% to 50% larger than Earth, with similar gravity.
The planet is perpetually faced with one side to its star, a phenomena known as tidally locked. Consequently, one side of the planet is exposed to perpetual daylight, another to darkness. It is unclear, at the moment, what the surface temperature is like on either side, because climate conditions, such as wind, would distribute surface temperature more evenly. Nonetheless, the daylight side is probably too hot for complex life (up to 71 Celcius, 160 Fahrenheit), as we know it, to flourish, while dark side resembles parts of Earth in wintertime, around -30 Celsius (-24 Fahrenheit).
The key to life, however, is on the "ring of life" that exists like a band between both sides, which experiences constant sunset environment and perfectly normal Earth-like temperatures. As you would move within this stretch from the more sunny side to the darker side, you would experience temperature changes exactly like those on Earth. This mysterious, alien environment is very stable, which is ideal for evolution of life.
If life had evolved in the same manner as it has on Earth, it would, by now, encompass almost the entire planet. On Earth, living organisms can be found in the most extreme conditions, provided they had time to adapt.
Unfortunately, we have no knowledge of its atmosphere, because it does not transit in front of its star from our perspective, which is a requirement set by the limited power of modern technology, to study an atmosphere of an exoplanet.
Given the abundance of water in the universe, the chances of water being present on the surface is very high, which would automatically be liquid due to the planetary climate.
Much is now known about its plantery system, which is reminiscent of our own. There are six confirmed planets in this system, which, in many ways, reseble planets in our own Solar System. It is safe to make the assumption that there are also moons, orbiting around some of these planets.
Zarmina's stability of climate suggests that if sentient/intelligent life had evolved there, it would be far ahead of us in its advancement due to age advantage. In which case, we wonder, when our own little world was discovered by them. The team's lead astronomer, Steven Vogt, a professor of astronomy and astrophysics at the University of California, has made a controversial statement that he is 100% positive that life exists on Zarmina.
Location of the system is 20 light years away, about 200 trillion kilometres. There are only approximately 100 stars in such proximity to Earth. This distance, in cosmic perspective, can be classified as "right around the corner." Even though that with modern technology, it is virtually unatainable, in one hundred years or so, it is conceivable that a probe will be sent in its direction.
In October 2008 a message from Earth was beamed, in international collaboration, from National Space Agency of Ukraine, in direction of Gliese 581 c, which is a neighbouring planet of Gliese 581 g (Zarmina), which was regarded as most Earth-like (just outside the habitable zone) planet, until the discovery of the planet in subject. The message will take 20 years to arrive there, any potential response will take another 20 years to get to Earth.
Discovery of an Earth-like planet finally allows scientists to make an educated guess on the frequency of habitable planets in the Milky Way Galaxy, they estimate the number to be in between 20 and 40 billions of planets. This estimate is beyond previous optimistic guesses.
There is little doubt that mankind will explore this planet in the distant future, colonization in the distant future is not out of the question either. Professor Steven Vogt calculates that it would take 200 years to get there using Nuclear Pulse Drive, which is close to our current technological capabilities. He proposes that works on such starship begin as soon as possible. It could either be fully automated with robotic artificial intelligence or contain a crew on a multigenerational mission.
Similar finds should become common in the common decades.
The planet is unofficially called Zarmina, in honor of the chief astronomer's wife.
Pulse of sharp light, resembling laser, was spotted coming from this planterary system in 2008, by an Australian astronomer Dr.Ragbir Bhathal.
Many are convinced that extraterrestrial civilizations are visiting our planet right now and have done so for as long as humanity existed. In fact, UFO phenomenon has a much greater popularity than Astrobiology does. Naturally, human mind is vigorously drawn to a possibility of contact with an advanced civilization of extraterrestrial origins. Searching for extremophile microbes for decades with no luck, on the other hand, offers much less excitement and requires greater scientific comprehension to appreciate.
People have always been seeing and attempting to contemplate strange lights in the skies. In the past, all we could do to explain our surroundings was use our imagination. Gradually, we had invented Gods that were responsible for various natural phenomenon. Our failure to understand nature forced us to invent inaccurate solutions to put our minds to ease.
Today, we still have mysteries that general population and sometimes even scientists cannot fully explain. Inventing new Gods fails to satisfy our curiosity and so we think of alternative explanations. Modern ufologists claim that approximately 20% to 5% of all unidentified flying object sightings cannot be ruled out as merely natural phenomenon. Their conclusion is that these are spaceships of interstellar origin.
In 1968, a corrupted hotel manager, Erich Anton Paul von Daniken, published a book called Chariots of the Gods? in which he presented his views on various archaeological findings. He concluded that Aliens had always been visiting Earth and that they had guided our civilization's progress. Archaeologists rejected his conclusions as those of an amateur lacking any understanding of the science of Archaeology. Despite having no qualifications to make claims that he did, his books and soon TV programs rapidly rose in popularity. Eventually he even opened a theme park Mystery Park where he offers visitors visual explanations of his remarkable findings. His ideas became further popularized by the media when the History channel launched a pseudoscientific show called Ancient Aliens.
Unfortunately, genuine Archaeology cannot compete in sensationalism with Ancient Aliens, even though the latter offers absolutely no evidence of extraterrestrial visitation of Earth at any point in human history. The same applies to the strange lights often observed by pilots. Being unable to understand something is proof of your inability to understand it, nothing more.
Extraterrestrial visitation of Earth is, in theory, possible. But there is no evidence for it. Even if we entertain the idea in a sober manner, we'd have to rely on our own pace and direction of technological progress to imagine capabilities of a civilization capable of efficient interstellar travel. Such civilization would be able to conceal its presence from us in its entirety, had it so wished, and we wouldn't spot its bright, flickering lights in the sky. It would not have its vehicles being crashed and "recovered" by the local authorities as a popular UFO-proliferator Stanton T. Friedman states. It would be able to do with us as it wished, either bless us with ultra-efficient energy sources, perhaps Fusion Power, or annihilate us in a second, in case of malicious intentions. It would have no need to conspire with our governments, as it would yield absolute power over us even if its advancement was only a few centuries ahead. However, considering the age of our Galaxy and our young species, it is more likely to presume that the different in development between different species would be measured in millions of years.
Recent conspiracy theories argue that visiting Aliens are experimenting on us, kidnapping millions of people, to somehow alter their failing genetics. Such ideas are entirely baseless, of course, and lack any coherency. More so, Humanity is now slowly approaching ability to alter its own genetics. Surely an Alien civilization capable of interstellar travel has mastered biotech to the point of total immortality.
Carl Sagan once said: For all I know we may be visited by a different extraterrestrial civilization every second Tuesday, but there's no support for this appealing idea. The extraordinary claims are not supported by extraordinary evidence.
If Extraterrestrials really were visiting Earth, whatever their intentions were, they would have already completed their goals. There is evidence for strange lights and other occurrences, but none at all in support of the UFO phenomenon.
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