Travel to Other Planets; "only possible by psychological changes in the mind"

The adaptability of organisms in different varieties of planets is described in the Brahma-saṁhitā as vibhūti-bhinnam, i.e., each and every one of the innumerable planets within the universes is endowed with a particular type of atmosphere, and the living beings there are advanced in science, psychology, etc., according to the superiority or inferiority of the atmosphere. Vibhūti means "specific power," and bhinnam means "variegated." Scientists who are attempting to explore outer space in an attempt to reach other planets by mechanical means must realize that organisms adapted to the atmosphere of the earth cannot exist in the atmospheres of other planets. As such, man's attempts to reach the moon, the sun, or Mars will be completely futile because of the different atmospheres prevailing on those planets. Individually, however, one can attempt to go to any planet he desires, but this is only possible by psychological changes in the mind. Mind is the nucleus of the material body. The gradual evolutionary progress of the material body depends on psychological changes within the mind. The change of the bodily construction of a worm into that of a butterfly and, in modern medical science, the conversion of a man's body into that of a woman (or vice versa) are more or less dependent on psychological changes.

In the Bhagavad-gītā it is said that if a man, at the time of death, concentrates his mind upon the form of the Personality of Godhead, Śrī Kṛṣṇa, and while so doing relinquishes his body, he at once enters the spiritual existence of the antimaterial world. This means that anyone who trains the mind to turn from matter to the spiritual form of the Godhead by performance of the prescribed rules of devotional service can easily attain the kingdom of God, in the antimaterial sky. And of this there is no doubt.
[By A.C. Bhaktivedanta Swami Prabhupada, from Easy Journey to Other Planets]
[http://prabhupadabooks.com/g=156037]