Is there extraterrestrial life? The early Greeks were the first Western masterminds to hypothesise the likelihood of there being a different universe facilitating life.
This hypothesis relies on the vast size and consistent physical laws of the observable universe.
According to this argument, made by scientists such as Carl Sagan and Stephen Hawking as well as well-regarded thinkers such as Winston Churchill  it would be improbable for life not to exist somewhere other than Earth.
Alternatively, life may have formed less frequently, then spread—by meteoroidsfor example—between habitable planets in a process called panspermia. Numerous discoveries in such zones since have generated numerical estimates of Earth-like planets —in terms of composition—of many billions.
One of the study authors, Sam Levin, notes "Like humans, we predict Extraterrestrials essay they are made-up of a hierarchy of entities, which all cooperate to produce an alien.
At each level of the organism there will be mechanisms in place to eliminate conflict, maintain cooperation, and keep the organism functioning. We can even offer some examples of what these mechanisms will be. It has been suggested that this capacity arises with the number of potential niches a planet contains, and that the complexity of life itself is reflected in the information density of planetary environments, which in turn can be computed from its niches.
Sufficient quantities of carbon and other elements, along with water, might enable the formation of living organisms on terrestrial planets with a chemical make-up and temperature range similar to that of Earth. It is also conceivable that there are forms of life whose solvent is a liquid hydrocarbonsuch as methaneethane or propane.
These six elements form the basic building blocks of virtually all life on Earth, whereas most of the remaining elements are found only in trace amounts.
The carbon atom has the unique ability to make four strong chemical bonds with other atoms, including other carbon atoms. These covalent bonds have a direction in space, so that carbon atoms can form the skeletons of complex 3-dimensional structures with definite architectures such as nucleic acids and proteins.
Carbon forms more compounds than all other elements combined. The great versatility of the carbon atom makes it the element most likely to provide the bases—even exotic ones—for the chemical composition of life on other planets.
Planetary habitabilityHabitability of natural satellitesand Exobiology Some bodies in the Solar System have the potential for an environment in which extraterrestrial life can exist, particularly those with possible subsurface oceans.
Important insights on the limits of microbial life can be gleaned from studies of microbes on modern Earth, as well as their ubiquity and ancestral characteristics.
If extraterrestrial life was found on another body in the Solar Systemit could have originated from Earth just as life on Earth could have been seeded from elsewhere exogenesis. The Nobel prize winner Francis Crickalong with Leslie Orgel proposed that seeds of life may have been purposely spread by an advanced extraterrestrial civilization,  but considering an early " RNA world " Crick noted later that life may have originated on Earth.
However, between an altitude of 50 and 65 kilometers, the pressure and temperature are Earth-like, and it has been speculated that thermoacidophilic extremophile microorganisms might exist in the acidic upper layers of the Venusian atmosphere. Life on Mars Life on Mars has been long speculated.
Liquid water is widely thought to have existed on Mars in the past, and now can occasionally be found as low-volume liquid brines in shallow Martian soil. Scientists have indications that heated subsurface oceans of liquid water may exist deep under the crusts of the three outer Galilean moons —Europa,    Ganymede     and Callisto.
Life on Europa Internal structure of Europa. The blue is a subsurface ocean. Such subsurface oceans could possibly harbor life. Enceladus Enceladusa moon of Saturn, has some of the conditions for life, including geothermal activity and water vapor, as well as possible under-ice oceans heated by tidal effects.
The temperature and density of the plumes indicate a warmer, watery source beneath the surface.Feb 15, · Winston Churchill, a longtime science enthusiast, at his home in Kent, England, in October He sent an essay to his publisher that month, just weeks after Britain entered World War II, .
This essay will provide a brief analysis of extraterrestrial events or evidence thereof the were especially significant.
THE BEGINNING OF LIFE Evolutionary theory suggests that life on earth has been developing for millions of years into more and more complex organisms. The scientific search for extraterrestrial life can be carried out directly and indirectly. In direct research, researchers look for “biosignatures” inside of the solar system.
To do this, they study surfaces from diverse planets and different items from space like shooting stars.
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Extraterrestrials Essay - Extraterrestrials Can the Earth be the only place in the Universe that harbors life. Most astronomers don't believe this is true.
Certain statistics in the Universe provide evidence that living beings may be common place through out the universe, on planets of other stars besides the sun. In this paper I plan to. The speculation of extraterrestrial intelligence is popular these days both in mass culture and in science but belief in extraterrestrial intelligence goes back into ancient times.
Extraterrestrial life is defined as life that does not originate from Earth.