Successfully colonizing the Red Planet will depend on three key technologies, or "killer apps," an expert said at a recent panel.

Those technologies will make it possible to get supplies to a potential Mars colony, said Philip Metzger, a planetary scientist at the University of Central Florida and a co-founder of NASA Kennedy Space Center's Swamp Works laboratory.

"I don't think there's really a viable case for colonizing Mars until after we after we get a supply chain established," he said. [How Will a Human Mars Base Work? NASA's Vision in Images]

This supply chain, Metzger said, will consist of three "killer apps" — profitable ventures that could serve as the economic stepping-stones to the Red Planet.

"Just like email — and, later, Facebook — were killer apps that made the internet economically viable, so there will be particular uses of space that will make the space industry economically viable," Metzger told Space.com. The killer apps he identified are mining asteroids for spacecraft propellant, building gigantic antennas in space to address Earth's exponentially growing internet data needs and beaming clean energy to Earth.

Metzger was speaking as part of the "Sustainable Expansion: Reaching Mars and Beyond" panel at the New Space Age Conference held on March 11 at the Massachusetts Institute of Technology (MIT) Sloan School of Management.

Panel members also included Jeffrey Hoffman, former NASA astronaut and director of MIT's Man Vehicle lab; Keegan Kirkpatrick, founder and team lead of RedWorks; and Mark Jernigan, associate director of the Human Health and Performance Directorate at NASA's Johnson Space Center in Houston. The panel discussed the economics of colonizing Mars.

There's some intrigue surrounding who will be the first to put boots on Mars, as NASA aims to get astronauts to the vicinity of the Red Planet in the 2030s, and a handful of other entities, such as Elon Musk's SpaceX, are drawing up their own Mars plans.

But it's best not to regard the effort as a race, NASA officials and other experts have stressed; for a permanent Red Planet colony to succeed, they have said, slow and steady might be the best pace. That slow pace will allow government and private entities to set up the necessary supply chain.

Metzger is pretty confident about the viability of the three supply-chain technologies, because he’s spent the last decade or so keeping a list of every idea anyone has suggested for making money in space.

"The craziest one I heard was to put a retirement home on the moon. That way, when people fall, they won't break their hip, [because they'll be] in low gravity," he explained to the conference attendees. "I don't see that one surviving."

Killer app #1: Mining asteroids for propellant

Mining asteroids has a business case right now, said Metzger. That case revolves around conventional satellites that use electric thrusters after launch to get into their geostationary orbits, located some 22,000 miles (35,400 kilometers) above the planet. That trip can take anywhere from six to 12 months. During that time, the satellite company is spending money on overhead costs and not making any revenue, Metzger said.

Asteroid mining offers a solution to that unused time, he said. A spacecraft would excavate the rocky material on an asteroid and then extract the water molecules that are chemically bound to the rock's clay minerals. Next, the craft would deliver the collected water to an orbiting depot, where the water would be split into its constituent hydrogen and oxygen, which can be used as rocket fuel. A space tug would then collect the fuel and rendezvous with a recently launched satellite, where the tug would inject the fuel and boost the satellite into its final orbit. [How Asteroid Mining Could Work (Infographic)]

If that boost can be done in less than a week, a satellite company would save hundreds of millions of dollars, Metzger said.

He said he has calculated the estimated cost of building the asteroid-mining spacecraft, the cost of the fuel depot, the cost of the space tug and the cost of operating all three of them. "Within a range of parameters, it comes out profitable," Metzger said.

Luxembourg has begun working on a similar project. The nation — the home base of SES, one of the world's largest satellite operators — announced plans last June to spend $223 million U.S. on asteroid-mining initiatives.

Killer app #2: 3D-printed space antennas

Humanity's demand for internet data doubles every 10.5 months. In about a decade, this demand will overtake capacity, and companies won't be able to lay new fiber-optic cables fast enough to keep up, Metzger said. Some companies, including SpaceX and OneWeb, are moving forward with plans to launch thousands of small internet satellites into low-Earth orbit, about 750 miles (1,200 km) up, to keep data flowing.

In low-Earth orbit, satellites move faster than the planet spins, never staying over the same location for very long. That means these low-Earth data satellites would have to hand off data to satellites coming up from behind. Because thousands of these satellites would work as a network, and because they would have limited capacity, the entire fleet would have to be replaced at the same time to handle increases in data.

"This solution is going to get us another couple of decades of internet, but it's not going to be a final solution," Metzger said.

He said he envisions giant space-based internet antennas 3D-printed from metal ore mined from asteroids. The technology for 3D printing objects in space is already being developed. With the help of a $20 million NASA contract, California-based company Made In Space is working with Northrop Grumman and Oceaneering Space Systems on a project called Archinaut, which aims to build a 3D printer that will assemble a large, complex structure in space by 2018.

A space-economy road map from United Launch Alliance (ULA), a joint venture between Lockheed Martin and Boeing, supports the viability of 3D-printed systems as well, suggesting that asteroid mining and space-based manufacturing could come online within the next five years. By 2045, ULA aims to have 1,000 people living and working in space, generating $2.7 trillion in revenue, company representatives have said.

The 3D-printed antennas would circle Earth in a geostationary orbit, that sweet spot about 22,000 miles up where objects move at the same rate as the planet spins. Each internet satellite would therefore be "fixed" over one location on Earth. If the data requirements for a particular city — Chicago, for example —increased, then satellites could be adjusted to split their beams and provide more capacity, Metzger said. [3D Printing in Space: A New Dimension (Photo Gallery)]

Ideally, the antennas would work as part of a multitiered system in which high-priority requests could be routed through fiber optics and low-Earth satellites, while less urgent needs could flow through geosynchronous satellites, he said.

"I've run the numbers on this. We could build a system in geosynchronous orbit that would provide 40 billion times today's data rate, which would supply Earth's demands all the way until the end of the century," Metzger said.

And companies could earn revenue doing this, he added. The internet is a trillion-dollar industry that's doubling every 10.5 months, Metzger said.

"Even if you capture [just] a small fraction of that industry within 30 years, you can achieve this $2.7 trillion target that United Launch Alliance is aiming for," he said.

Killer app #3: Beaming clean power to Earth

Solving Earth's data demand won't solve all of humanity's computing problems, however. A report last year by the Semiconductor Industry Association and Semiconductor Research Corporation concluded that, by 2040, computers will use up all of the available energy on the planet. Humanity therefore needs to look beyond Earth for a sustainable energy source.

In 2012, John Mankins received funding from the NASA Innovative Advanced Concepts program to develop his idea for an orbiting array of thin, movable mirrors that would beam solar power to Earth.

Mankins — a former scientist at NASA's Jet Propulsion Laboratory and now the president of Artemis Innovation Management Solutions in Santa Maria, California — proposed that the array's components be manufactured on Earth and then launched into space. But that could cost trillions up front, making it difficult for the project to attract investors, Metzger said. Manufacturing the system in space could be the most economical approach, he added.

"If we do the first killer app, propellant mining, then that leads into the second killer app, which is making large antennas in space," said Metzger. "We will reach the point that we can build these space based-solar-power systems without having to launch everything."

By that point, the space-based economic engine will be humming along. People will then be able to diversify, he said. More infrastructure and more industries would then be able to move into space, making it less necessary to launch supplies into orbit, Metzger said.

"Eventually, you get a complete supply chain," he said.

And the more industry there is in space, he said, the easier it will be to build spacecraft to colonize Mars.

"I'm very optimistic about this," Metzger said.

You can follow Tracy Staedter at her website tracystaedter.com and @tracy_staedter. Follow us @Spacedotcom, Facebook and Google+. Original article on Space.com.