NASA is planning a mission to Mars in coming decades. And this week, a group of scientists announced a new effort to discover extraterrestrial life. At the launch of the new initiative to find ET, physicist Stephen Hawking said, “there is no bigger question” than whether we are alone in the universe.

Consider how the discovery of alien intelligence would alter our understanding of our place in the cosmos. The old stories that put humanity at the middle of things would be radically transformed by the discovery of alien intelligence. Intelligent aliens would not know about Moses, Jesus, or Mohammed. An encounter with intelligent aliens would likely relegate revealed religion to the dustbin of history.

Now some may suggest spreading the good news of earthly revelation to other worlds. But we should be cautious about the urge to evangelize. How would we like it if ET came to earth with tales of an alien religion?

The history of colonial expansion here on earth gives us a reason to worry about the urge to explore the stars. Will we pollute, exploit and despoil the planets we colonize? Until we can prove that we won’t harm alien worlds, we should be cautious in our explorations. Let’s be good stewards of this planet before we venture beyond it.

We also have a difficult time treating terrestrial “aliens” well. We are not great at dealing with immigrants, strangers and nonhuman animals. Our tendency toward xenophobia, ethnocentrism, and anthropocentrism may cause problems if we make contact with extraterrestrials.

We should get our own house in order before leaving home. For too many earthlings, the biggest question is how to find food, water and happiness. For suffering humans, space exploration is a distraction from the terrestrial afflictions of war, poverty, despair and hate.

Consider what earthlings must look like from an extraterrestrial vantage point. Billions of us are hungry. We continue to kill each other in large numbers. And we are destroying our own habitat and changing earth’s climate. If ET is watching, she would have good reason to keep her distance.

Fifty years ago, at the dawn of the space age, Aldous Huxley, the author of “Brave New World,” expressed similar reservations. Huxley was critical of the idea of “man conquering space.” He cautioned against seeing ourselves as conquerors. Instead, he imagined that space exploration could help us develop a kind of cosmic consciousness. The hope is that we would learn to act as “responsible collaborators with the evolutionary process that is perpetually creating, transforming, and transfiguring the world.”

It is amazing that billions of years of terrestrial evolution have allowed earthlings to see Pluto. In one lifetime we have made it to the edge of the solar system. We must now decide whether we are conquerors or compassionate collaborators with the cosmos.

Hawking and others imagine that alien life must have evolved independently on some other planet in our vast universe. But at this point, as far as we know, intelligence is a unique product of terrestrial evolution. Understanding this should give us pause. We ought to be extremely careful with this precious gift. The universe may not get another chance to create an intelligent species like our own.

As far as we know, we are a singular species poised precariously on a rock careening through empty space. Understanding this, we ought to care more deeply for one another and for this planet. Our existence is the lucky outcome of a unique configuration of gravity, liquid water and freedom from the onslaughts of space debris.

The icy geography of Pluto teaches us that life is precious and fragile. As we begin exploring the galaxy, we also need to explore inner space — the heart and the mind. And we need clean up our own planet before leaving it behind.