This Christmas marks the 50th anniversary of Apollo 8, the first human journey from the Earth to the Moon. Its remarkable technological and organizational accomplishments notwithstanding, Apollo 8 remains best remembered for the new perspective it offered on humanity’s place in the cosmos. The three-man crew’s Christmas Eve message, broadcast from lunar orbit back to “all of you, all of you on the good Earth,” continues to inspire, and astronaut Bill Anders’s stunning “Earthrise” photo remains etched on humanity’s collective consciousness as the first time we witnessed the beauty and fragility of our home planet from afar.

Blasting off during dark times for the United States, and the world, Apollo 8 serves as a potent reminder of what space exploration was and can be again: a beacon of hope for the future and a wellspring of faith in the better angels of human nature, even in the face of grim and foreboding circumstances. Indeed, the spirit of Apollo 8 can offer Democrats and progressives strong guidance as they navigate—and hopefully chart a course beyond—the dire straits in which the nation finds itself today. Now more than ever before, it’s vital that Democrats and progressives advance their own forward-looking and optimistic vision for America’s space program.

For its part, the Trump Administration has taken space policy in a dangerous direction. Its proposal to create a Space Force as a new and unnecessary branch of the armed services threatens to erase the civilian face of America’s space program and replace it with a military one. Vice President Mike Pence—chair of the National Space Council—has already blurred the conceptual boundaries between NASA-led space exploration and the Administration’s Space Force proposal. Combined with President Trump’s bellicose rhetoric, the Administration’s military-heavy space policy threatens to transform President John F. Kennedy’s warning that space could be a “new terrifying theater of war” from a prophecy into reality.

Beyond this incipient transformation of the nature and focus of America’s space policy, the Trump Administration has also shifted NASA’s primary focus away from ambitions for a human voyage to Mars and toward a return to the Moon instead. Little of substance has changed—NASA’s Deep Space Gateway, for instance, was first rechristened the Lunar Orbital Platform-Gateway and is now simply called the Gateway—and NASA budgets remain roughly where they were at the end of the Obama Administration. But this seeming continuity, and the current Administration’s preoccupation with a return to the Moon, obscures this national retreat from the far more ambitious goal of sending astronauts to Mars.

It’s not enough for Democrats and progressives to simply oppose Trump’s space policy and leave him with a political monopoly on the subject by default. They must put forward their own ambitious vision of space exploration that offers a credible and inspiring alternative to Trump’s policies. Democrats and progressives should support space exploration as an example of what we as a nation can do when we pull together to achieve a common goal for the benefit of all.

Indeed, Democrats and progressives ought to consider themselves the rightful heirs of America’s space exploration ambitions. It was President Kennedy, after all, who challenged the nation to put a man on the Moon, before it had blasted an astronaut into orbit. President Lyndon B. Johnson carried Apollo forward, despite the financial and political demands imposed by the war on poverty, the war in Vietnam, and a myriad of other national priorities. Too often since, however, Democrats and progressives have paid little attention to space exploration despite lauding the achievements of our astronauts and robotic explorers.

In the age of Trump, however, this progressive neglect has become malign and its time they start paying attention. Conservatives and Republicans have been all too eager to seize the mantle of space policy leadership, showing the desperate need for a forward-looking alternative that appeals to America’s best self rather than to our fears.

Space exploration not only represents the best of what America is and can offer the world, however—it’s a much-needed public investment in American science and technology. Indeed, Apollo-era investments in research and development paid off just as well as other federal R&D efforts. The development of the Apollo Guidance Computer, for instance, fostered demand for new and untested silicon microchips—the very same components that play such a critical role in our economy and society today. Equally important, a robust civilian-led program of human and robotic space exploration allows the United States to write the rules of the celestial road through its own actions in space.

So what should a progressive and Democratic space exploration policy look like?

First and foremost, Democrats should not be afraid to be bold and ambitious. Sending astronauts to Mars should be America’s main human spaceflight goal, not the comparatively pedestrian return to the Moon promoted by the Trump Administration. There’s little to be gained in terms of national pride and international standing from going back to a destination the United States was able to reach with the technology available in the 1960s. By contrast, human voyages to Mars can, as President Kennedy put it, when he spoke of the country’s first voyage to the moon, “serve to organize and measure the best of our energies and skills” as a nation.

But human spaceflight is just one half of the equation when it comes to America’s space exploration policy. Robotic explorers from Voyager to Galileo have plumbed the depths of the gas giants in the solar system, while rovers and landers like Curiosity and the recently arrived InSight have given humanity tantalizing glimpses of the Martian surface. Along with the Hubble Space Telescope and NASA’s other Great Observatories orbiting overhead, these robotic missions have vastly expanded humanity’s knowledge of its own celestial neighborhood and the universe at large. They are among the nation’s crown jewels, worthy of protection and further investment.

More high-mindedly, an ambitious Democratic progressive space exploration policy can serve as positive source of national pride—something progressives sorely need in this political day and age. At its best, a progressive space exploration policy can help build an optimistic and constructive patriotism that stands in sharp contrast to the poisonous brand of nationalism put forward by President Trump and his acolytes. Moreover, NASA presents an excellent opportunity for public R&D investment outside the confines of the Department of Defense and its military-focused research.

Still, this sort of inspiration isn’t free. Over the last two decades, NASA has made due with annual budgets that have fluttered around $20 billion, adjusting for inflation. The sort of ambitious progressive space exploration policy sketched above will require more resources for NASA. But not that much more: Democrats should call for an additional $5 billion per year in funding for NASA, with $3 billion dedicated toward human spaceflight and $2 billion toward robotic exploration missions. That’s peanuts compared with the $150 billion in annual revenue that’s being forgone by the federal government over the next decade as result of the Trump tax cuts. Given the tangible and intangible benefits from a bold space exploration program, this is a small price to pay.

So as the nation marks the 50th anniversary of Apollo 8, it’s worth reflecting on the sometimes forgotten fact that space exploration delivers much more than aerospace jobs or moon rocks. It widens our horizons as a nation and a species, and fosters a positive and unifying sense of national purpose. Today, Democrats and progressives could stand poised to recapture the spirit of space exploration embodied by Apollo 8—but only if they put forward a bold, ambitious, and optimistic vision for space exploration.