Imagine you’re trying to decide where to place your peg in a game of Battleship. Except let’s change it up a bit. Instead of looking at a small grid, you’re scanning an entire planet. And instead of looking for ships, you’re trying to find evidence of microscopic life. And let’s add another fun twist: There might not even be any actual “targets” for you to find.

Sound like something you’d be willing to bet more than $2 billion on? Well, NASA’s doing it anyway.

NASA announced that it has locked on to the landing site for its next Mars rover, to be launched in 2020. The destination: an ancient lake bed known as the Jezero crater. It’s a hugely expensive gamble intended to uncover the secrets of our planetary neighbor’s cryptic past — and it’s likely we will end up with more questions than answers.

And yet, this is among the most exciting space missions of our lifetime.

“I think, in the long run, this will be a no-brainer,” Thomas Zurbuchen, associate administrator at NASA, said. As head of the agency’s science mission directorate, he’s the man who called the multibillion-dollar shot, shaping the search for life beyond our planet for the near future.

Zurbuchen recognizes that the mission comes with risk. NASA plans to land the rover in the crater using a rocket-powered sky crane — a mind-blowing maneuver in which a spacecraft barrels into Mars’ atmosphere at breakneck speeds and, with the help of a parachute and propulsion rockets, slows down just enough to lower the rover onto the surface on cables in midair. Such a landing isn’t unprecedented, but engineers refer to the procedure as “seven minutes of terror.”

Complicating matters is rough terrain full of boulders and sand dunes. And even if the rover manages to land without a hitch and secure the samples it set out to collect, there’s no guarantee that they’ll ever be delivered to Earth for study. The plan is to launch another rocket to Mars in the future to retrieve those samples and bring them to Earth, but such missions have yet to be funded.

Zurbuchen also knows that plenty of scientists disagree that Jezero is the best place to look for signs of ancient life on Mars. Others, for example, have proposed returning to the hot springs in the planet’s Columbia Hills, where our Spirit rover explored almost a decade ago. Spirit didn’t have the tools needed to search for life, but it did find structures similar to those created in part by extremophile bacteria in hot springs on Earth.

But in the end, only one landing site could be chosen, and Jezero was determined to be the best bet.

After all, if evidence of long-lost Martian life exists, it would make sense that it would be somewhere where there was once shallow water — hidden in the dried-up clay of the lake bed.

The Jezero mission is more than just a daunting engineering feat. It represents the first rover mission designed to seek signs of life beyond Earth. And if everything goes according to plan, it will be the first round-trip mission to another planet — a first step before humans make the trip themselves.

And so, in a way, the mission represents hope. At a time when government can’t seem to accomplish very much at all, and when human beings don’t seem to agree on even the most basic values, space missions such as this reach for other worlds and promise to do the impossible. The odds for finding evidence of life beyond our atmosphere are low, but they don’t keep the most brilliant among our species from trying.

Mars is a dead world — cold and windswept with unrelenting storms. For one reason or another, it shed its magnetic field when it was only 500 million years old. Soon thereafter, sunbeams stripped away its atmosphere, drying up its vast oceans and rendering its surface unbearable for any potential life.

Perhaps it never was bearable. Perhaps we’ve always been alone in this corner of the cosmos. But now, for the first time, we’re scraping together the machinery to test that theory directly.

“These are the things that pivot humanity,” Zurbuchen said. “The seafarers who crossed the ocean — is it critical that they did that? Absolutely.”

For centuries, humankind has been aiming at targets we don’t know exist. But we fire anyway, over the horizon. We might fail to find evidence of life on Mars, but the act of seeking it will be a great accomplishment nonetheless.

Robert Gebelhoff is an assistant editor for The Post’s Opinions section.