The dream of putting a human colony on Mars is undergoing a quiet revival in the United States.

Scientists from government, industry and universities have been thrashing out the problems and possibilities at a series of conferences in recent years.

Their conclusion: Only a lack of money and political will are holding back humanity's next great space adventure.

"If we wanted to put people on Mars, it could be done by the mid-1990s," says Leonard David of the private National Space Institute here.

Although a Mars mission soon seems unlikely, members of a new National Commission on Space, which includes former astronauts and politicians, say it appears to be only a matter of time until a manned Mars shot occurs.

The commission, appointed by President Reagan, is due to present a report next May outlining what it thinks the U.S. space program should look like over the next 20 years.

Officials of the National Aeronautics and Space Administration say the agency is only starting to consider the possibility of a manned Mars mission.

The United States last visited Mars in 1976, when unmanned Viking 1 and 2 missions landed and began collecting data. The Mars Observer is due to blast off in 1991 for studies of the planet from orbit.

Beyond that, NASA officials said, there is nothing concrete on the drawing board, although they are considering sending an unmanned craft to land on Mars, collect samples and return in a manner similar to early moon explorations.