Are We Alone in the Universe?
There are more Stars in the Universe than all the Grains of Sand on Earth

Are We Alone in the Universe?
There are more Stars in the Universe than all the Grains of Sand on Earth

The existence of life elsewhere in the universe is highly likely. In fact, the chances that Earth is the only place in the universe with life is considered completely improbable.

But where this life exists elsewhere is a mystery, due to the vast size of the universe.

There was a dramatic shift in thinking initiated by the invention of the telescope and the Copernican assault on geocentric cosmology.

Once it became clear that the Earth was merely one planet amongst countless bodies in the universe, the extraterrestrial idea moved towards the scientific mainstream.

The best known early-modern proponent of such ideas was the Italian philosopher Giordano Bruno, who argued in the 16th century for an infinite Universe in which every star is surrounded by its own planetary system.

Bruno wrote that other worlds "have no less virtue nor a nature different to that of our earth" and, like Earth, "contain animals and inhabitants".

The possibility of extraterrestrials remained a widespread speculation as scientific discovery accelerated. William Herschel, the discoverer of Uranus, was one of many 18th–19th century astronomers convinced that the Solar System, and perhaps others, would be well-populated by alien life.

Other luminaries of the period who championed "cosmic pluralism" included Immanuel Kant and Benjamin Franklin. At the height of the Enlightenment, even the Sun and Moon were considered candidates for extraterrestrial inhabitants.

For fifty years, the Search for Extraterrestrial Intelligence has been scanning the galaxy for a message from an alien civilization. So far to no avail, but a recent breakthrough suggests they may one day succeed.

The discovery of planet
Gliese 581 c is a marvelous discovery. It shows how close we are getting to planets that remind us of the Earth. Gliese 581 c or Gl 581 c is an extrasolar planet orbiting the red dwarf star Gliese 581. With a mass of at least 5.36 times that of the Earth, it is classified as a super-Earth and is approximately 20.3 light-years from our Earth.

NASA hopes to find 50 more Earth-like planets by the end of the decade, all of which increases the chance that alien life has begun elsewhere. There are well over 500 billion planets within the universe.

For scientists, the vastness of the universe means just one thing. The existence of life. But proving it is not that simple.

Alien Life on Titan or Europa

Titan's landscape and surface similarities with
Earth could shed valuable light on what sparked the life explosion on Earth, and how possible it might be for life to exist on other planets.

NASA and ESA plan two major missions to the icy moons of Jupiter and Saturn, beginning in the year 2020. Will ET life finally be exposed?

For years, humans have wondered if they were the only intelligent species in the universe. Does intelligent life exist elsewhere?

It is estimated that at least 50 billion galaxies are visible with modern day telescopes. Scientists believe that there are many more galaxies in the universe which we cannot see with our current technology.

It is estimated that there are at least ten thousand, billion, billion, stars in the universe which is properly known as ten sextillion.

It is estimated that there are at least ten million, billion, planets in our universe. But in all reality there are probably many more that we cannot possibly ever see due to the vast size of the universe.

The amount of moons in the universe is unknown. Current technology has a hard enough time detecting a planet let alone a moon but estimates of one trillion moons could be within our universe.

With these many galaxies, stars, planets and moons is it logical to say that we are the only planet in this universe to support intelligent life? No, it is not logical to assume this.

Scientists have long speculated that there could have been life on Mars at one point, possibly intelligent life. If life currently exists on Mars, it would most likely be some form of microbial life.

No evidence has proven or disproved that there was life on Mars at one point. Logically, it is very possibly that there was life on Mars, and it has been speculated that this life may have been quite different compared to what life is like here on Earth.

Scientists have long speculated about the possibility of life on Mars owing to the planet's proximity and similarity to Earth.

Although fictional Martians have been a recurring feature of popular entertainment, it remains an open question whether life currently exists on Mars, or has existed there in the past.

Mars' polar ice caps were observed as early as the mid-17th century, and they were first proven to grow and shrink alternately, in the summer and winter of each hemisphere, by William Herschel in the latter part of the 18th century.

By the mid-19th century, astronomers knew that Mars had certain other similarities to Earth, for example that the length of a day on Mars was almost the same as a day on Earth.

They also knew that its axial tilt was similar to Earth's, which meant it experienced seasons just as Earth does - but of nearly double the length owing to its much longer year.

These observations led to the increase in speculation that the darker albedo features were water, and brighter ones were land. It was therefore natural to suppose that Mars may be inhabited by some form of life.

In 1854, William Whewell, a fellow of Trinity College, Cambridge, who popularized the word scientist, theorized that Mars had seas, land and possibly life forms.

Speculation about life on Mars exploded in the late 19th century, following telescopic observation by some observers of apparent Martian canals — which were however soon found to be optical illusions.

Despite this, in 1895, American astronomer Percival Lowell published his book Mars, followed by Mars and its Canals in 1906, proposing that the canals were the work of a long-gone civilization.

This idea led British writer H. G. Wells to write The War of the Worlds in 1897, telling of an invasion by aliens from Mars who were fleeing the planet’s desiccation.

Spectroscopic analysis of Mars' atmosphere began in earnest in 1894, when U.S. astronomer William Wallace Campbell showed that neither water nor oxygen were present in the Martian atmosphere.

By 1909 better telescopes and the best perihelic opposition of Mars since 1877 conclusively put an end to the canal theory.

Scientists are directly searching for evidence of unicellular life within the Solar System, carrying out studies on the surface of Mars and examining meteors which have fallen to Earth. A mission is proposed to Europa, one of Jupiter's moons with a possible liquid water layer under its surface and might contain life.

There is some limited evidence that microbial life might possibly exist (or have existed) on Mars.

An experiment on the Viking Mars lander reported gas emissions from heated Martian soil that some argue are consistent with the presence of microbes. However, the lack of corroborating evidence from other experiments on the Viking lander indicates that a non-biological reaction is a more likely hypothesis.

Independently, in 1996, structures resembling nanobacteria were reportedly discovered in a meteorite, ALH84001, thought to be formed of rock ejected from Mars. This report is controversial.

In February 2005, NASA scientists reported that they had found strong evidence of present life on Mars.

The two scientists, Carol Stoker and Larry Lemke of NASA's Ames Research Center, based their claims on methane signatures found in Mars' atmosphere resembling the methane production of some forms of primitive life on Earth, as well as on their own study of primitive life near the Rio Tinto river in Spain.

NASA officials soon denied the scientists' claims, and Stoker herself backed off from her initial assertions. Though such findings are still very much in debate, support among scientists for the belief in the existence of life on Mars seems to be growing.

In an informal survey conducted at the conference at which the European Space Agency presented its findings, 75 percent of the scientists in attendance were reported to believe that life once existed on Mars, and 25 percent reported a belief that life currently exists there.

Are We Alone?

In November 2011, NASA plans to launch the Mars Science Laboratory (MSL) rover which is designed to search for past or present life on Mars using a variety of scientific instruments.

The MSL is scheduled to land on Mars at Gale Crater in August 2012.

The Gaia hypothesis stipulates that any planet with a robust population of life will have an atmosphere in chemical disequilibrium, which is relatively easy to determine from a distance by spectroscopy.

However, significant advances in the ability to find and resolve light from smaller rocky worlds near their star are necessary before such spectroscopic methods can be used to analyze extrasolar planets.

On March 5, 2011, Richard B. Hoover, an astrobiologist with the Marshall Space Flight Center, speculated on the finding of alleged microfossils similar to cyanobacteria in CI1 carbonaceous meteorites. However, NASA formally distanced itself from Hoover's claim.

In August 2011, findings by NASA, based on studies of meteorites found on Earth, suggests DNA and RNA components (adenine, guanine and related organic molecules), building blocks for life as we know it, may be formed extraterrestrially in outer space.

Many bodies in the Solar System have been suggested as being capable of containing conventional organic life.

The most commonly suggested ones are listed below; of these, five of the ten are moons, and are thought to have large bodies of underground liquid (streams), where life may have evolved in a similar fashion to deep sea vents.

  • Mars — Life on Mars has been long speculated. Liquid water is widely thought to have existed on Mars in the past,
    and there may still be liquid water beneath the surface. Methane was found in the atmosphere of Mars. By July 2008, laboratory tests aboard NASA's Phoenix Mars Lander had identified water in a soil sample.

    The lander's robotic arm delivered the sample to an instrument which identifies vapors produced by the heating of samples. Recent photographs from the Mars Global Surveyor show evidence of recent (i.e. within 10 years) flows of a liquid on the Red Planet's frigid surface.
  • Mercury — The MESSENGER expedition to Mercury has discovered that a large amount of water exists in its exosphere.
  • Europa — Europa may contain liquid water beneath its thick ice layer. It is possible that vents on the bottom of the ocean warm the ice, so liquid could exist beneath the ice layer, perhaps capable of supporting microbes and simple plants, just like in Earth's hydrothermal vents.
  • Jupiter — Carl Sagan and others in the 1960s and 70s computed conditions for hypothetical amino acid-based macroscopic life in the atmosphere of Jupiter, based on observed conditions of this atmosphere. These investigations inspired some science fiction stories.
  • Ganymede — Possible underground ocean.
  • Callisto — Possible underground ocean.
  • Enceladus — Geothermal activity, water vapor. Possible under-ice oceans heated by tidal effects.
  • Titan (Saturn's largest moon) — The only known moon with a significant atmosphere. Data from the Cassini-Huygens mission refuted the hypothesis of a global hydrocarbon ocean, but later demonstrated the existence of liquid hydrocarbon lakes in the polar regions - the first liquid lakes discovered outside of Earth.

    Analysis of data from the mission has uncovered aspects of atmospheric chemistry near the surface which are consistent with – but do not prove – the hypothesis that organisms there are consuming hydrogen, acetylene and ethane, and producing methane.
  • Venus — Recently, scientists have speculated on the existence of microbes in the stable cloud layers 50 km above the surface, evidenced by hospitable climates and chemical disequilibrium.

  Are we alone in the universe? Many scientists believe that we are not. The chances that our planet is the only planet in the entire universe that contains life is very slim. It is widely believed within the scientific community that if life is discovered, it would most likely be on a moon orbiting a planet.

Most scientists believe that there is some form of life elsewhere in the universe such as bacteria but discussing such topics as intelligent life is generally frowned upon. It is these types of actions from scientists which make the general population believe that science is biased.

In reality, there is a very high chance that intelligent life exists within our universe and some groups as well as individuals believe this intelligent life is already observing our actions here on Earth.


Numerous other bodies have been suggested as potential hosts for microbial life. Fred Hoyle has proposed that life might exist on comets, as some Earth microbes managed to survive on a lunar probe for many years.

However, it is considered highly unlikely that complex multicellular organisms of the conventional chemistry of terrestrial life (i.e. animals and plants) could exist under these living conditions.

Even if microbial extraterrestrial life were found on another body in the Solar System, it would still need to be proven that such life did not originate from Earth in the recent or distant past.

For example, an alternate explanation for the hypothetical existence of microbial life on Titan has already been formally proposed — theorizing that microorganisms could have left Earth when it suffered a massive asteroid or comet impact (such as the impact that created Chicxulub crater only 65 mya), and survived a journey through space to land on Titan 1 million years later.

The Living Interplanetary Flight Experiment, developed by the Planetary Society and due to be launched in 2011, has been designed to test similar theories.