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The Big Bang took place 14 billion years ago, the Solar System was formed 4 and a half billion years ago, and the first hominids appeared 60 million years ago. Life on other planets may have started, evolved, given birth to extraterrestrial intelligences, and perhaps even faced a planetary extinction event millions or even billions of years ago.
n e = 1 to 5 (stars with planets will have between 1 and 5 planets capable of developing life) f l = 1 (100% of these planets will develop life) f i = 1 (100% of which will develop intelligent life) f c = 0.1 to 0.2 (10–20% of which will be able to communicate) L = somewhere between 1000 and 100,000,000 years
Planetary habitability in the Solar System is the study that searches the possible existence of past or present extraterrestrial life in those celestial bodies. As exoplanets are too far away and can only be studied by indirect means, the celestial bodies in the Solar System allow for a much more detailed study: direct telescope observation, space probes, rovers and even human spaceflight.
However, what makes a planet habitable is a much more complex question than having a planet located at the right distance from its host star so that water can be liquid on its surface: various geophysical and geodynamical aspects, the radiation, and the host star's plasma environment can influence the evolution of planets and life, if it ...
When scientists are looking for worlds that might harbor life on other planets, they tend to look for worlds that have features similar to Earth's. It makes sense; after all, our dominant theories ...
This is also called the habitable zone, when a planet is the right distance from its star to have a comfortable temperature and liquid water pooling on its surface. For possible life on other ...
On the other side of this are those scientists of the time who rejected Pasteur's results and instead supported the idea that life on Earth came from existing life. This necessarily requires that life has always existed somewhere on some planet, and that it has a mechanism of transferring between planets.
Several other planets, such as Gliese 180 b, also appear to be examples of planets once considered potentially habitable but later found to be interior to the habitable zone. [ 1 ] Similarly, Tau Ceti e and f were initially both considered potentially habitable, [ 67 ] but with improved models of the circumstellar habitable zone, as of 2022 PHL ...