Thus the "faith" in Nietzsche's formula is not an epistemic state concerning supernatural entities or metaphysical propositions. It is a fidelity to sublimated instinct - an "ethos" in the sense of knowing where you are coming from. And all earthlings come from the Earth. Religions have traditionally devalued "the world" and valued instead certain dreams of other so-called "perfect" worlds. There is no planet in our solar system even close to supporting plant life, let alone our more complex forms. To think that we can leave the Earth and go somewhere else is no less a form of reality-denying nihilism than traditional religious beliefs. In either case, Nietzsche's warning that we maculate conception with the doctrine of immaculate conception resonates across all sorts of nihilisms, religious and secular.
"Remaining true to the Earth" means admitting that either we get things right on this planet, or we don't get things right at all. The Earth represents our one and only window of opportunity, at the same time as it symbolizes all of our unknown higher potentials. Neither spaceman nor God will come to save us. But this is not a bleak dystopian materialism, because just as our simian ancestors couldn't realize that the development of their vocal cords (something they already had at least in rudimentary form) would open up those new dimensions of reality that we call language, civilization, and culture, just so we ourselves cannot yet get our minds around what we might be able to do already in rudimentary form - both with our own bodies and with the planet as a whole. "Faith in the Earth" means always remembering that whatever developments might lay in store they will exist in this world, so their very possibility depends entirely upon each generation's maintenance of the biosphere, including the atmosphere. An amazing future is depending upon us.
Thus Faith in the Earth takes the old conception of religious faith - that we are the love objects of a divinity - and replaces it with a higher, less servile conception of our proper dignity - that we are links in the chain connecting our simian ancestors with a higher type of descendant, or Übermensch. We can no more understand what that will be than they understood us. But we can understand that just as our arrival depended upon our simian ancestors, likewise the Übermensch is depending upon us. This higher sense of dignity fits in with Nietzsche's general revaluation of those values distorted by religion's otherworldly delusions: love becomes love for Earthlings (both animals and Übermenschen included along of course with us); hope becomes hope for this Earth, and the hope that we Earthlings will not ruin it; charity becomes the overflowing virtue of generosity linked inextricably to amor fati and to creativity itself; and faith becomes remaining true to the Earth, and faithful to its unfathomed possibilities.