Malin Moller, 8, and her mother, Julie Moller, of Capitol Hill, walk through a neutron simulator at the USA Science & Engineering Festival in Washington on Friday. (J. Lawler Duggan/For The Washington Post)

Students from around the world explored the surface of Mars on Friday, examining the craggy outcrops of the Martian horizon and rocks smoothed by waters that once flowed on the Red Planet’s surface.

No, they weren’t actually on the surface of Mars, but it was the next-best thing. Students from the District, Houston, New Jersey, Buenos Aires and Managua, Nicaragua, joined in on a virtual field trip with NASA experts, looking at images beamed back from the rover Curiosity as part of an event that helped open this weekend’s USA Science and Engineering Festival at the Walter E. Washington Convention Center.

The festival — which is free and open to the public — features an array of hands-on science experiments, enormous futuristic machines, atomic-particle games, drones, light shows and countless educational exhibits.

Friday’s preview attracted hundreds of students, including Tyshoun Barber, an eighth-grader at the District’s Kramer Middle School. Barber was among a group of youngsters learning about the rover from NASA scientists who helped design and build Curiosity, the nuclear-powered robot equipped with lasers than can zap rocks more than 20 feet away.

Barber and students from around the world were able to join together online through a Google video chat, and they examined astronaut’s gloves, played with models of robots and rovers, and pored over photographs of Mars and images of Earth from space.

Barber said he wants to visit Mars some day and said he’d take along one thing: a dove.

“I’d bring a dove with me to keep in mind that Earth is still my home,” said Barber, 14. “It’s a symbol of peace.”

NASA engineer Lisa May said the agency’s latest efforts seek to broaden scientific understanding of Mars, the fourth planet in line with the sun and Earth’s closest planetary neighbor.

May, a leader of NASA’s Mars program, said that early in her career, Mars was known as little more than “a formless ball of red stuff.” During the past decade, scientists have uncovered significant evidence suggesting that Mars might have been habitable to life as we know it. May said that analysis of data from Curiosity show that lakes on Mars once had water so pure that humans could drink it through a straw.

Jim Green, NASA’s planetary science division director, said that such findings make scientists confident that they one day will prove life beyond Earth could exist or has existed in our solar system.

“We’re on the precipice of discovery,” Green said. “I think our best bet is at Mars.”

On the trail are two rovers operating on the Martian surface, including Opportunity, which landed in 2004, and Curiosity, which touched down in 2012. Standing seven feet tall and weighing 2,000 pounds, Curiosity is equipped with state-of-the-art sensors and cameras that capture the landscape in fine detail. The robot, which cost $2.5 billion to develop, already has covered more than five kilometers of Mars in its exploration of the dry and arid planet, which is about half the size of Earth.

The students on Friday learned that Curiosity’s recent measurements indicated a maximum temperature of 6 degrees below zero Fahrenheit, relatively mild considering that the coldest days on Mars reach 225 degrees below zero.

Green said that what surprised many NASA scientists about Mars is its similarities to Earth. Mars once had clouds and weather. There were once vast bodies of water.

“If we had microbes from Earth planted there they would grow, multiply and survive,” Green said, noting that mounting evidence suggests that life once existed on Mars. But then something happened, Green said: Martian climate change.

John Feeley, a deputy assistant secretary of state for Western Hemisphere affairs, said the virtual field trip showed how international relations are crucial for future space endeavors.

“We live in a globalized world,” Feeley said. “Not one country or society will have the answers to global warming or the mysteries of space.”

Many of the students taking part in the discussion Friday asked Green about the Martian environment and whether humans will one day bounce across its surface. [Because of the low effect of gravity on Mars, a 100-pound person on Earth would weigh only 38 pounds there.]

Green said that NASA is drafting plans to send another rover to Mars by 2020. This time, the robot will drill into the surface, retrieve core samples and scoop up rocks that one day will be rocketed back to Earth for a hands-on examination.

By 2030, NASA hopes to send humans to Mars. But it’s a long trip. Depending on its orbital position, Mars is, on average, about 140 million miles from Earth. It likely will take two years to make the round trip. Once there, Green said that the astronauts will investigate the planet’s geology, seeking clues that could solve some of the mysteries of the early cosmos.

Feeley said those first Earth visitors to Mars could be students who are now the same age as Barber.

If trends hold, Feeley said, those historic interplanetary explorers probably will “take a selfie and send it back to Earth.”