LAUREL, Md. — The first close-up image of Pluto has revealed mountains as tall as the Rockies, and an absence of craters — discoveries that, to their delight, baffled scientists working on NASA’s New Horizons mission and provided punctuation for a journey nine and a half years in the making.

Only 112 years after the Wright Brothers were barely able to get their airplane off the ground, a machine from Earth has crossed the solar system to a small, icy world three billion miles away. The flyby on Tuesday, when New Horizons buzzed within 7,800 miles of the former ninth planet, came 50 years to the day after NASA’s Mariner 4 spacecraft made a similar first pass by Mars.

Pluto until a few weeks ago was a blurry dot. Within the past couple of days, it has been transformed into a dynamic world with varied geography, discoveries that point to the possibility of ice volcanoes and churning tectonics. All of this new information could provide clues to how planets form and even to the origins of some of the building blocks of life.

“I don’t think any one of us could have imagined that this could have been a better toy store,” S. Alan Stern, the mission’s principal investigator, said during a news conference on Wednesday.