Long before men's journey to Mars was planned, NASA and the AMES Research Institute already have an idea how a space colony would look like.

In 1975, NASA commissioned a study to produce images of potential space colonies design. At that time, NASA is looking at building space colonies in the year 2100. And with the advancement of space science, it looks like NASA is still on track with its plans.

NASA released the photographs 40 years ago. Potential floating colonies were seen and were then intended to be built by the year 2100.

"If we as a people decide to do it, we can do it. We have the scientific capability, financial capability, there is simply no question we can do it," said Dr. Al Globus, contractor for the NASA Ames research center, in a statement.

The study contains various images of floating cities, including a cylindrical colony which is capable of housing one million people at a time.

A team of architects, researchers, scientists and engineers led by Princeton Professor Gerard O'Neill, assessed the ideas and were then rendered by artists into illustrations. Artists Rick Guidice and Don Davis drew the three potential space colony designs in 1975.

The images produced were considered as "retrofuturistic." The designs include sustainable food farming and artificial gravity according to a report by CNN.

From the published paper, the team also thought of reflecting the rays of the sun to illuminate the colony with natural lighting. Aside from the colony, part of the study suggests that in order for the space colony to thrive, space transport for human beings should be developed. This is now out of the questions since spacecraft can now transport crew from Earth to the International Space Station (ISS) and vice-versa.

According to the study, called "Space Settlements, A Design Study," space colonization is considered due to limited resources on the planet and the growing population of its residents. And that space offers resources and growth for mankind.