NASA held the first annual SpaceCom Expo on Nov. 17, during which the U.S. space agency's administrator Charles Bolden emphasized the need for commercial companies' investments to make the planned manned mission to Mars successful.

Bolden spoke of the importance of private companies to the future of NASA missions in terms of supporting space science and astronauts.

"Now that the doors have been kicked open, I'm looking forward to new ideas about what we do next and how we keep that market humming," Bolden said.

The NASA chief was among the SpaceCom speakers who discussed the need for private companies to help the space agency manage the responsibilities of supporting space stations and creating new laboratories in space.

NASA is committed to lending support to the International Space Station (ISS) until 2024, but Bolden emphasized that while the agency wishes to pursue other more ambitious goals, such as sending humans to Mars, it will need more resources than it can afford.

"As we focus on sending humans to Mars, it will likely be commercial companies and international partners who assume a lead role in taking humans back to the surface of the moon," he said.

Bolden hopes that — with the full support of government and private companies — commercial crew capsule flights to space could become reality by 2017, and that NASA will no longer have to depend on other nations to send crew to space.

Some commercial companies, such as NanoRacks and Made In Space, have already sent small experiments to the ISS or made contributions to experiments conducted in the orbiting laboratory.

Made In Space's Zero-G Printer, for instance, became the first manufacturing device to be sent and used in space.

The ISS is considered by many as an important research source not just in terms of space science — the zero-gravity environment also provides a unique testing hub for different types of physical, biological and chemical experiments.