What is Astrobiology?Explain the criteria.

Explanation

(i)Astrobiology/Exobiology is the science which looks for the presene of extra terrestrial life in the Universe.
(ii)It deals with the origin,evolution and distribution of life in the Universe and to investigate the possibility of life in other world.
(iii)The major concept is the habitable zone. The theory ecplains that any planets can support the existence of life ,if it fulfills two important criteria,that is :
(a)It must have a right mass to retain an atmosphere.
(b)It must have an orbit at just the right distance from its Star (sun)THat it allows liquid water to exist.Thus ,the distance need to be neither too hot hot or not too cold and is often referred as Goldilock Zone for life.
(iv)In our solar system .Earth. is the only planet in the Goldilock Zone.Since ,this zone varies at times as the star evolves,we know that mars have also been habitable.The life on mars are likely to be the creatures,we find in extreme enviroments on earth.