The expected flyby of NASA’s New Horizons spacecraft past Pluto and its moons on Tuesday marks an end of an era of space exploration. But there are so many more discoveries to be made in our solar system. And as the species achieves what once seemed only the glimmer of possibility in reaching Pluto, it’s impossible to not wonder: What should NASA do next?

One day in the future, perhaps we’ll study scientific questions about space by flying on solar sails from one corner of our solar system to another, or making the Kessel Run in less than 12 parsecs. For now, planning these major explorations takes a lot of time and planning -- and money. NASA has some big plans in the years ahead -- sending a better lander to Mars or launching a spacecraft to study Jupiter’s moon Europa more closely. But planetary scientists and advocates of exploration have imaginations that go beyond NASA’s budgetary and political limits. And they have some ideas for what humanity might do next that matches or even exceeds the scale and complexity of what the New Horizons mission to Pluto is trying to attain.

Carolyn Porco, leader of the imaging science team on the Cassini probe mission, is ready for a return to Saturn’s orbit. She thinks that one priority should be a return trip to our planet with samples from Enceladus, an icy moon orbiting Saturn that was found to have a deep sea beneath its surface. Such a mission could possibly help answer a profound question about whether there are signs of life anywhere else in our solar system.

“The tools on Earth are far more sophisticated than anything we can send to Saturn,” she said. “We could do a bang-up job.”

Another advocate of exploration of our solar system wanted to look beyond Saturn, but not quite as far as Pluto and the Kuiper belt objects that New Horizons might now study.

Emily Lakdawalla, the senior editor of the Planetary Society, said she hoped Neptune and Uranus might receive more attention in our exploration of the solar system. While she admitted to being a fan of underdogs, she offered scientific reasons to study the ice giants, too. Notably, the eventual arrangement of the planets shaped the Kuiper belt and the movement of comets deeper into our solar system, activities that have had major implications for our species.

“They all get back to the big question of how did we get here?” she said. “Planets of this size are very important in the origin and development of our solar system.”

Many scientists are also eager to more deeply study bodies beyond our solar system. One, Sara Seager of M.I.T., described the growing interest among scientists and the public more broadly.

“There’s a huge, growing groundswell of people who are just so excited about the search for other planets,” she said. “This is a real step in the direction of trying to understand if we’re alone out there.”

Dr. Seager works with NASA to study a proposal called a starshade, which would help telescopes see these planets by blocking out the light of their stars, making them more visible. The ability to complete such a project, she said, is our best opportunity in the near term to identify an Earth-like planet.

These experts have their own varying reasons for favoring one major space exploration project over another. Now we want to know what you think NASA’s next major priority should be. Select your preferred mission and make your case. We’ll highlight some of the best replies on NYTimes.com soon. A Times journalist may use your email address to contact you, but it will not be published.