SpaceX CEO Elon Musk presented his grand plan of colonizing Mars during the International Aeronautical Congress held in Guadalajara, Mexico on Tuesday amidst an enthralled audience.

The plan involves building a spacecraft that could ferry 100 people to the Red Planet, a reusable mega-rocket touted to be the world's most powerful, a giant transporter, and an overall architecture that would enable humanity to establish a permanent, self-sustaining colony on Mars within the next 50 to 100 years.

The ambitious plan had drawn mixed reactions from experts and different questions were raised regarding the viability of Musk's vision.

Could humans survive the trip?

While SpaceX's Interplanetary Transport System (ITS) promises the Mars trip to be "fun," with a movie theater and a restaurant to keep passengers from getting bored, the biggest concern is how to keep these people alive throughout the trip. According to NASA, deep space contains high levels of radiation from solar flares and cosmic rays that could harm humans during space flight.

Musk may think of the radiation problem as "not too big of a deal," but not for space experts. "Radiation-he maybe down played it a little more than I would have. It's not a show stopper, but you have to worry about solar flares," Chris McKay, a planetary scientist at NASA Ames Research Center, told The Verge.

How will spacefarers live and how will they survive on the Martian surface?

 The ITS will carry the colonists to the Red Planet and provide the opportunity to create a "self-sustaining civilization" on the planet. But it is not clear where exactly the people will live on Mars, how the Martian habitats will be created and what technologies are needed to survive on the surface of the planet.

According to John Logsdon, an expert on space policy, such technology is still in its infancy and supporting a huge colony of people will require support systems like food and energy supply. These systems would require huge amount of funding, which SpaceX might not be able to manage alone.

How will SpaceX shorten the Martian trips?

 Musk said that the colonial spaceship would journey between 80 to 150 days, whereas NASA estimates that the shortest Martian trip could take more than half a year long.

"I couldn't quite follow where that was coming from," Bobby Braun, an associate professor of space technology at the Georgia Institute of Technology, told The Verge. "I think it'd be very hard to get there in the transfer times that he mentioned. When we send robotic missions to Mars, they tend to take nine months to get there."

Insane but NOT impossible

 While Musk's Mars colonization plan may sound crazy for some, there are those who believe the mission is not unachievable.

"There's no technical obstacle to the plan being executable," Logsdon said. "SpaceX has good engineers. They don't have to really invent much."

In his plan, Musk said the spacecraft would take humans to Mars and back to Earth using fuel made from methane propellant plants to be built on the Red Planet. Prior to the Musk's presentation, SpaceX already announced that they are working on a rocket engine that would run on methane/oxygen propellant, which was said to be a more readily available fuel on Mars.

"I don't think they are practical in the form he presented them, but with a little modification, they could be made practical and very powerful," Robert Zubrin, leader of the space advocacy organization Mars Society, told Space.com.

Who's prepared to die?

 During the Q&A session in the conference, a clever question was thrown at Musk: "Who should these people be, carrying the light of humanity to Mars for all of us?" Musk was honest enough to say that the journey will be "very dangerous" and that "the risk of fatality will be high." But he did mention one criterion in selecting the first humans to set foot on Mars: "Are you prepared to die? If that's okay, then you're a candidate for going."