(WASHINGTON) -- It’s been a lofty goal America's leaders have set their sights on for generations, and President Donald Trump kicked off his second term by restating his goal of reaching the Red Planet.
"And we will pursue our Manifest Destiny into the stars, launching American astronauts to plant the Stars and Stripes on the planet Mars," he said during his Jan. 20 inauguration speech.
Elon Musk -- the CEO of space technology company SpaceX -- has the president's ear this time around, suggesting we'll see an even harder push to make the 140 million-mile journey to Mars.
"Can you imagine how awesome it will be to have American astronauts plant the flag on another planet for the first time?" Musk said on Inauguration Day.
It will take a herculean effort from NASA to make a mission to Mars a reality, experts told ABC News. It must build on the Artemis program -- which Trump established in 2017 to build a human presence on the moon -- to get people setting foot on Mars, according to NASA.
"NASA’s current moon to Mars exploration approach calls for using missions on and around the moon under the Artemis campaign to prepare for future human missions to Mars," an agency spokesperson said in a statement sent to ABC News. "We’re looking forward to hearing more about the Trump administration's plans for our agency and expanding exploration for the benefit of all, including sending American astronauts on the first human mission to the Red Planet."
However, the mission can't simply launch whenever the crews and technology are ready. Scott Hubbard ran the agency's Mars program from 2000 to 2001, served as director of its Ames Research Center for 4 years and was in executive management at NASA for 20 years.
He noted that there are specific windows for when to launch the mission. When Earth and Mars align in their orbits around the sun, the distance and energy required for a spacecraft to travel to Mars are minimized.
The next window is just a year and a half away.
"Even with the most powerful rockets we have, there is a window of 20 days every 26 months," he told ABC News. "And that's it. I mean, it's literally be there or forget about it."
Whenever the mission takes off, it will be an incredibly challenging endurance test filled with problems never encountered before, requiring a crew of astronauts daring enough to make the journey.
Astronauts Barry "Butch" Wilmore and Sunita "Suni" Williams have been getting a taste of that. The pair have been in space for nine months, with their planned 8-day trip to the International Space Station (ISS) getting an unexpected extension for safety reasons.
"So once we transitioned from not returning on our spacecraft, we transitioned into being a crew member, on the international crew, members on the International Space Station," Wilmore told ABC News. "And that's what we've been doing since we've been here."
Williams noted that this kind of flexibility will be key for anyone hoping to go to Mars.
"I'd say nothing goes as planned and be ready for that," she told ABC News. "You know, a little challenge, a little adversity brings out the best in us."
This experience may one day be useful to astronauts making the 7-month journey to Mars, their fellow ISS crew member Nick Hague told ABC News.
"You know, being up here, it's not about a singular mission. It's not about a singular trip to Mars," he said. "We're part of a long legacy of exploration, of human exploration, of space, and we're doing our little part to try to advance that."
The ISS crew is researching some of the logistical challenges that the long journey to Mars would present.
"How do we sustain ourselves? We can't pack all the resources we need on a trip to Mars and sustain a long mission," Hague said. "So we're going to have to figure out how to grow the food that we're going to need."
The astronauts would also need to be able to replace equipment that breaks during the trip.
"So you cannot take every single spare part with you," Wilmore said. "You're going to have to have some way of additive manufacturing -- 3D printing."
The trip would also expose astronauts to conditions that could lead to multiple health problems, including the potential risk of cancer and mental health issues, along with bone and muscle problems, space physiologist Rihana Bokhari told ABC News. Getting messages back to Earth could take a while as well, she noted.
"That communication delay is going to be quite large when it comes to Mars, about 20 minutes each way at the furthest," she said.
Setting foot on the fourth planet from the sun may be the goal, but it's only half the battle. A round-trip mission would take at least three years.
"In addition to transportation, you need a habitat. We have not yet built a place for astronauts to live for the 6 or 7 months it would take to get there and have a really reliable life support," Hubbard, the former NASA Mars lead, told ABC News.
Hubbard believes NASA should be thinking longer term for its first manned mission to Mars.
"Not all opportunities are equal," he said. "And if you were to look out to 2033, you see an opportunity that comes only once every 15 years. You can get the most mass to Mars of any of these other 20-day windows."
Considering the length of time for the window from now, Hubbard noted that the Apollo missions followed a similar timeline -- from the first tests in 1961 to Apollo 11 landing on the moon in 1969.
"And it's going to take not just technological advancement but political will," he said. "It's going to take people to see that this is part of what we do as human beings."
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