What is "panspermia"

Panspermia \Pan`sper"mi*a\, Panspermy \Pan"sper`my\, n. [Pan- + Gr. ? a seed.] (Biol.)

1. The doctrine of the widespread distribution of germs, from which under favorable circumstances bacteria, vibrios, etc., may develop.

2. The doctrine that all organisms must come from living parents; biogenesis; -- the opposite of spontaneous generation.

3. The theory that life on earth originated from spores or germs that evolved elsewhere in the uiniverse; -- in contradistinction to the theory that life evolved on earth from inanimate matter. This theory, originally suggested by S. Arrhenius in 1907, is sometimes advanced by those who feel that the time required for evolution of life is too long for life to have evolved on Earth from inanimate matter.

n. The hypothesis that microorganisms may transmit life from outer space to habitable bodies; or the process of such transmission.

Panspermia is the hypothesis that life exists throughout the Universe, distributed by meteoroids, asteroids, comets, planetoids, and, also, by spacecraft in the form of unintended contamination by microorganisms.

Panspermia is a hypothesis proposing that microscopic life forms that can survive the effects of space, such as extremophiles, become trapped in debris that is ejected into space after collisions between planets and small Solar System bodies that harbor life. Some organisms may travel dormant for an extended amount of time before colliding randomly with other planets or intermingling with protoplanetary disks. If met with ideal conditions on a new planet's surfaces, the organisms become active and the process of evolution begins. Panspermia is not meant to address how life began, just the method that may cause its distribution in the Universe.

Pseudo-panspermia (sometimes called "soft panspermia" or "molecular panspermia") argues that the pre-biotic organic building blocks of life originated in space and were incorporated in the solar nebula from which the planets condensed and were further—and continuously—distributed to planetary surfaces where life then emerged ( abiogenesis). From the early 1970s it was becoming evident that interstellar dust consisted of a large component of organic molecules. Interstellar molecules are formed by chemical reactions within very sparse interstellar or circumstellar clouds of dust and gas. The dust plays a critical role of shielding the molecules from the ionizing effect of ultraviolet radiation emitted by stars.

The chemistry leading to life may have begun shortly after the Big Bang, 13.8 billion years ago, during a habitable epoch when the Universe was only 10–17 million years old. Though life is confirmed only on the Earth, some think that extraterrestrial life is not only plausible, but probable or inevitable. Other planets and moons in the Solar System and other planetary systems are being examined for evidence of having once supported simple life, and projects such as SETI are trying to detect radio transmissions from possible alien civilizations.