On March 21 of this year, both parties in Congress and the Trump administration made a change to a federal document that amounted to only a few words, but which may well change the course of human history.

Every few years, Congress and the administration pass a NASA Authorization Act, which gives the U.S. Space Agency its marching orders for the next few years. Amongst the many pages of the 2017 NASA Authorization Act (S. 422) the Agency’s mission encompasses expected items such as continuation of the space station, building of big rockets, indemnification of launch and reentry service providers for third party claim and so on. But in this year’s bill, Congress added a momentous phrase to the agency’s mission: “the search for life’s origins, evolution, distribution, and future in the universe.” It’s a short phrase, but a visionary one, setting the stage for a far-reaching effort, that could have as profound an impact on the 21st century as the Apollo program had on the 20th.

NASA’s new directive acknowledges that we are tantalizingly close to answering perhaps the most fundamental question of all: Are we alone in the universe? We have wondered about this for millennia. As early as 300 B.C., Epicurus postulated that there must be many worlds like ours among the stars. But until very recently, we didn’t know if other planets even existed beyond our own solar system.

In the last decade however, we have made enormous advances in the field of exoplanet studies. Telescopes on the ground have become sensitive enough to discern the faintest stellar “wobbles,” as orbiting planets tug gently against their gravitational bonds. With the National Science Foundation’s Atacama Large Millimeter Array, and the Hubble Space Telescope, we have peered into interstellar clouds where new planets are forming and have detected the presence of all the elements necessary for life.

New discoveries are coming fast and furious. On February 23, 2017, NASA announced that a nearby star system, TRAPPIST-1, has seven planets orbiting it, three of which lie within the star’s “Goldilocks zone,” making them potentially habitable. And on April 19, the Harvard Smithsonian Center for Astrophysics and the European Southern Observatory announced the discovery of a “super Earth”—a rocky, planet 40-percent larger than Earth, orbiting a red-dwarf star just 39 light years away. Indeed, we are finding thousands of planets orbiting other stars. Data from NASA’s Kepler Space Telescope suggests that almost every star in the sky has at least one planet around it. We may even find extraterrestrial life in our own solar system: Both Jupiter’s moon, Europa, and Saturn’s moon, Enceladus, have liquid water beneath their icy crusts, and on April 13, 2017, NASA announced that its Cassini Spacecraft discovered molecular hydrogen in water plumes emanating from Enceladus, indicating the presence of two key requirements for life—liquid water and a source of energy.

With all of these discoveries and with 1023 stars in the universe, it would seem statistically very likely that life exists in some of these alien solar systems. Indeed, in June of last year, The New York Times acknowledged this new perspective with an optimistic piece titled, “Yes, There Have Been Aliens.”

But not so fast. As Ross Andersen argued in a rebuttal to that New York Times article, these optimistic statistics and promising discoveries can’t tell us for sure that we aren’t alone. The only place we know life exists is here on Earth. And yes, on our planet it is tenacious—thriving 20,000 feet down, where strange organisms flourish on deep-sea vents without sunlight or oxygen, and 20,000 feet up, where cacti and insects have found a niche in the Atacama Desert. And yes, it is also resilient, adapting to ponds as corrosive as battery acid and feeding off radioactive waste in Chernobyl. And yet, we don’t know how life actually began here on Earth. Additionally, modern DNA analysis tells us that complex life, anything beyond a single cell organism, resulted from a random “event” in which two cells came together to form eukaryotes—something that apparently happened only once in the 4.5-billion-year history of our planet. Every worm on a deep sea vent, or cactus eking out an existence in the high Andes, every human who hunted on the plains or stood on the moon owes their existence to a single chance meeting of two cells that learned to get along.

There may be billions of Earth-like planets out there that are abundant with all the elements for life, but that doesn’t mean that there is life, let alone complex life on any of them. The only way to answer the question, “are we alone?” is to go see for ourselves, and this is exactly what NASA has now been empowered to do.

Of course, NASA has had spectacular successes since the Apollo era, building huge machines like the Shuttle and International Space Station, landing audacious vehicles on Mars, and visiting every planet in our solar system with robotic probes. But there has long been a yearning for NASA to rediscover the sense of purpose it had in the Apollo era, a unified goal that can reconnect the divisions of the agency and point them towards a grand and inspiring goal. The agency now has a chance to reconnect its divisions at an extraordinary time in the Space Agency’s history.

NASA has been putting in place all the necessary building blocks to make the Search for Life possible. NASA’s James Webb Space Telescope (JWST), due to launch in late 2018, will begin following up on recently discovered exoplanets, searching for “the fingerprints of life,” gases that scientists believe can only exist in the presence of living organisms. And NASA and private industry have embarked on ambitious new rockets capable of carrying probes and landers to Europa, and launching future telescopes capable of finding and characterizing continents and oceans on Earth-like planets. Soon, they will be able to send  (human) geologists and biologists to Mars.

Imagine a world in 2040, where NASA and its partners in industry and academia across the world have been unified, and perhaps rewarded by this search. Imagine that the Europa orbiter and subsequent lander survived the harsh conditions on Europa, only to discover that the cracks in the ice-mantle show evidence of organic life. Imagine the first Martian geologists find fossils of early organisms reminiscent of a pre-eukaryotic Earth. In addition to these results, imagine that the larger successor to JWST a few years earlier has found, in the reflected light of its own sun, a wet, rocky Earth 2.0, where biology is at work. Our world-view will have been irreversibly changed by these discoveries and we will be motivated to find a way to bridge the great distances and go to this new world. This is not outside the realm of possibility. By 2040, it’s possible that we will have designed a fusion rocket engine capable of accelerating a probe to a significant percentage of the speed of light.

What will we find when we get there? Even small variations could create different evolutionary paths. Perhaps we will find a planet very much like Earth, but one on which dinosaurs still roam because no killer asteroid has wiped them out. Or we may find the ruins of an advanced civilization, which would confront us with the deeply troubling possibility that civilizations that have evolved before us have destroyed themselves once they came to dominate their home planet.

What’s next? This is an important question, one that speaks not only to us humans as explorers, but ultimately to our long-term survival. Thanks to NASA’s pivot to include the search for life, young people who are living today may get the chance to answer it.