A group of Russian space experts says it is planning a privately financed manned mission to Mars.
The plan is for a three-year round trip to Mars
One of the team, Georgy Uspensky, of the Central Research Institute for Machine Building, said it would happen within 10 years and cost $3-5bn.
Aerospace Systems, a commercial company seeking to fund the project using private capital, suggested it could involve a reality TV show.
But Russia's official space agency has dismissed the project as nonsense.
The plan is for six cosmonauts to take a three-year round trip, including several months exploring Mars.
The spaceship would be equipped with its own garden, to supply them with fresh fruit and vegetables.
The experts said the craft would use parts already tried and tested on the International Space Station.
It would be put together in orbit, centred on two inflatable modules with living space for a crew.
Mr Uspensky said the plan - for which the estimated costs would be a fraction of those incurred by the US on its proposed manned mission to Mars - had "good business potential".
A real-time TV serial could be made from the lives of the crew, made up of both men and women, which could provide a return on investments in the project, the experts said.
But a spokesman for Russia's federal space agency said the project was unworkable.
"I don't believe it is possible to carry out a manned expedition to Mars for this amount of money and in this timeframe," Sergey Gorbunov said.
Earlier this week, the US authorities issued a licence for the first time to a company hoping to make a manned sub-orbital spaceflight in a privately owned and developed rocket plane.
The licence clears the way for an attempt on the X-prize for the first privately funded, non-governmental body that can launch a three-person craft into space twice in two weeks.