Life on other planets

Q: Is there life on only planets?
A: The Rambam in his letter to the Sages of Marseilles wrote that there are three ways to investigate an issue: through prophetic revelation, intellect and experience (Igrot Ha-Rambam, Rav Shilat Edition, p. 479). Regarding our question, nothing is explicitly written either way in the Torah or Prophets. This is not surprising since the Torah is not a science book, but a guide for what is right and wrong. In order to understand reality, we have scientific intellect, which is also a Divine gift, and there is even a blessing upon seeing a great scientist: Blessed is Hashem…who gave of His wisdom to flesh and blood (Shulchan Aruch, Orach Chaim 224:7). We are not opposed to the concept of life on other planets, as Rabbi Chasdai Crescas mentioned at the end if his book "Or Hashem," but we do not have any conclusive scientific proof. We are therefore left with experience.
It is amazing that over the last fifty years people have been talking about aliens. Hundreds of thousands of people have testified that they saw an alien or spaceship, but there has still not been a scientific declaration that they exist. Why is this so? No museum possesses an alien or spaceship to investigate. There is a basic scientific principle that any assumption must be examined and analyzed to prove or disprove it. Committees have been established to investigate eyewitness claims, and all of them been explained in some fashion: a plane, missile, meteorological air balloon, helicopter in fog, secret military devices, shooting star, low clouds, etc… Science does not accept anything without proof but it also does not reject anything without proof. Over fifty years of investigations and there is no decisive proof either way, but the field of science-fiction literature is booming.
A tremendous debate whether there was life on the moon raged throughout America and the world's scientific community before the scheduled manned landing by the Apollo 11 Lunar Excursion Module. Before this "one small step for mankind" actually transpired, opinions flew as to the possibility of life in space. It was perhaps a hypothetical question until – from the most unexpected quarter – someone not from the scientific community expressed a definitive answer. This outspoken expert was none other than the Satmar Rebbe – Ha-Rav Yoel Teitelbaum – who exerted with total certitude that there was no life on the moon. And where, many wished to know, did this scholar, not famous for astrological insight glean this information? The Satmar Rebbe said that if there was life on the moon, the Ponevizher Rav – Ha-Rav Yosef Shlomo Kahaneman, who was a most successful fundraiser for his yeshiva in Bnei Brak, would have gone there collecting!" (Builders by Chanoch Teller, p. 352).
We must remember that the Torah is not a science book. Whether there are aliens is not the subject of the Torah. Our subject is how man needs to act in this world. Science comes to describe the world. The Torah does not come to describe what is, but what should be. The Torah does not come to describe if there is life on other planets, but how to have a pure soul and to be a holy and righteous person on this planet (Maharal in Netivot Olam – Netiv Ha-Torah, Netiv 14).