Asaññasattaa — realm of mindless beings who have only bodies without consciousness. Rebirth into this plane results from a meditative practice aimed at the suppression of consciousness. Those who take up this practice assume release from suffering can be achieved by attaining unconsciousness. However, when the life span in this realm ends, the beings pass away and are born in other planes where consciousness returns.http://www.accesstoinsight.org/lib/auth ... el322.html
Hi Sarath ,
A few years , i felt that beings in the mindless planes ( rupa ) , ( like some of the high mountains , and some as the astral and celestial bodies ) , may have arisen in these planes , owing to their foundation of sila , and extensive samadhi , they may also have had a dislike to the ills of the changing nature of the mind , hence they come into existence of a plane devoid of the mind . On a parallel , beings that come into the existence in the formless planes ( arupa planes ) with only the nutritive contents of the mind to sustain the immense longevity , these beings may have had the dependence of sila and extensive samadhi , with a probable base of dislike to the various ills and afflictions that material form gets along with it .Thus the unending chains of causes and effects , for such planes to arise.
The Buddha mentions , that for full liberation the pre-requsite of both mind and matter is an essential dependence to gain fruition.