The Discovery has returned to Earth after its 39th and final mission — marking the beginning of the end of the three-decade space-shuttle program.

And, perhaps, a misguided US retreat from space exploration.

True, President Obama last year committed the US to landing an astronaut on an asteroid and a manned orbit of Mars.

But both those missions are nearly two decades away — at the earliest.

The value of probing space shouldn’t be underestimated: What can be learned from the cosmos — and even from the mere process of exploring it firsthand — can lead to revolutionary new applications for everyday life. And, of course, satisfy a basic human curiosity.

It can also help maintain a nation’s world status.

Given the lack of funding, if Americans resume manned flights, it will either be onboard private crafts (not entirely a bad idea) or with the aid of countries like Russia, which plans to build an $800 million spaceport.

But the US shouldn’t shortshrift space.

As for the soon-to-be-retired shuttle fleet, we can only reiterate what we’ve said before: One of the three spacecraft should be given a permanent home at the Intrepid Sea, Air and Space Museum on Manhattan’s West Side.