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Panspermia has its roots in Greek. The word means "seeds everywhere". The Panspermia theory proposes that the "seeds" of life exist all over the Universe and can be propagated through space, from one star system to another. Some believe that life on Earth may have originated through these "seeds". How life originated on earth is a question that people have meditated upon for as long as we can remember. Where did we come from? How did we get here? What are the origins of the human species? What is the origin of life? These questions have plagued mankind's consciousness for eternity. Theories aplenty, from ones based in religious doctrine, to the ones from the scientific realm to others that are on the fringes of science fiction.
A possibility that hovers on this horizon is the Panspermia theory, which proposes that life on Earth did not actually originate on our planet, but was transported here from elsewhere in the universe. This idea seems straight out of a science fiction novel, however, there is some evidence suggesting that life may have its origins in extraterrestrial beings. The Earth has been heavily bombarded during a period between 4. 0 and 3. 8 billion years ago. Researchers believe the Earth endured a very powerful and long series of meteor showers.
Evidence for earliest forms of life on Earth show their presense around 3. 8 billion years as well, which makes it reasonable to postulate that all life would have faced extinction during this heavy bombardment period. Life on earth can withstand extreme conditions. Microbes have known to survive temperatures as low as -18°C. Bacteria has grown at a temperature as high as 113°C. In fact, many can be frozen in liquid nitrogen for preservation. Some life is able to tolerate high doses of UV and ionizing radiation, extreme pressure, abrupt and radical temperture shifts etc. These observations suggest that life's preferable and favored conditions for thriving are difficult to define and predict. Life does not seem to be unique to Earth, as it has been found on meteorites that land on Earth. The presence of water elsewhere in the universe reinforces this.
Mars is believed to have contained water in the past. Much excitement for the presence of life on Europa, one of Jupiter’s moons, has been fueled by speculations that it may have underground oceans. Water is essential for life. It is the most common molecule in the Universe as it is formed of the most common elements in the Universe, Hydrogen and Oxygen. However, while water is essential for life that we are familiar with, its presence does not necessarily indicate the presence of life. Organic matter is common in space. This fact could also support the idea of extraterrestrial life. Organic matter refers to matter composed of compounds that contain Hydrogen, Oxygen, and Carbon. All living things on Earth are carbon-based. An assortment of organic compounds has been discovered in meteorites that have landed on earth, including amino acids, which are the building blocks of proteins (and proteins are primary components all of the living cellular machinery). The presence of carbon-based matter in meteorites supports the possibility that life on our planet could have come from the depths of space. But, even though life on earth is composed of organic matter, organic matter itself is not considered life.
Organic matter arrives from other plants and could have taken shape here. Panspermia Propagation Methods Panspermia propagation methods include the diversion of interstellar dust by solar radiation, gravitational pressure, and extremophile microorganisms jazzing around through intra-stellar space. The French nobleman, diplomat and natural historian Benoît de Mailleti in 1743, postulated and believed that life on Earth was "seeded" by organisms from space falling into our blue oceans, rather than life arising through abiogenesis. The theory of panspermia appeared in the works of the nineteenth-century scientists Jöns Jacob Berzelius (1779–1848), Lord Kelvin (William Thomson) (1824–1907) and Hermann von Helmholtz (1821–1894). "[W]e must regard it as probable in the highest degree that there are countless seed-bearing meteoric stones moving about through space. If at the present instance no life existed upon this Earth, one such stone falling upon it might, by what we blindly call natural causes, lead to its becoming covered with vegetation. " Lord Kelvin declared in 1871. Professor Francis Crick, winner of the Nobel prize, a British molecular biologist, physicist, and neuroscientist, along with British chemist Leslie Orgel, proposed the theory of directed panspermia. In a paper entitled "Lithopanspermia in Star Forming Clusters" published April 29, 2005, cosmologists Fred C. Adams of the University of Michigan Center for Theoretical Physics and David Spergel of the Department of Astrophysical Sciences of Princeton University proposed the lithopanspermia hypothesis in star-forming groups and clusters, in which the chances of biological material propagating from one star system to another is greatly enhanced due to their close proximity.
Terrestrial planets are often blasted by asteroids and comets large enough to hurl a rock at speeds exceeding escape velocities. Minerals in rocks can shield microbes from shock and radiation (associated with impact craters) as well as hard radiation from the Sun as stony meteors move through space. The strongest forms of life seem to have the ability to survive in a cold vacuum by going into a stasis – a reducing of chemical activity and metabolism to zero while maintaining biological structure well enough to later unfreeze and multiply in more salubrious environments. Hypothesizing that life can be seeded into one solar system in a young cluster, either by direct biogenesis or through an encounter with bio-invested material from outside the genesis aggregate.
Subsequent dynamical interactions among the constituent solar systems can then allow life to spread throughout the birth cluster, Adams and Spergel conclude that". . . young star clusters provide an efficient means of transferring rocky material from solar system to solar system. If any system in the birth aggregate supports life, then many other systems in the cluster can capture life bearing rocks.
"Three popular variations of the panspermia hypothesis are: Lithopanspermia (interstellar panspermia)Impact-expelled rocks from a planet's surface serve as transfer vehicles for spreading biological material from one solar system to another.
Ballistic panspermia (interplanetary panspermia) Impact-expelled rocks from a planet's surface serve as transfer vehicles for spreading biological material from one planet to another within the same solar system. Directed panspermia The intentional spreading of the seeds of life to other planets by an advanced extraterrestrial civilization, or the intentional spreading of the seeds of life from Earth to other planets by humans.
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