But Nasa administrator and former astronaut Charles Bolden has now said engineers are 'a lot closer than ever before' in making this dream a reality.
He recently told Congress that nuclear thermal propulsion is 'the most effective' way of sending humans to Mars and believes reaching the red planet by 2030 will ensure the survival of our species.
Speaking to CNBC's 'On the Money,' Bolden said: 'We think we're on the right trajectory to get humans to Mars in the 2030s.'
The US' top space official said he is now confident Nasa's 'Journey to Mars' will be accomplished because the past 50 years of missions act as a precursor to the mission to the red planet.
He said the mission is 'critically important' in helping us understand our own planet better, because Mars has the same amount of dry land as Earth, with seasons, weather and volcanoes.
While no liquid water has been found, evidence suggests water exists in the planet's icy soil and thin clouds, raising hopes that traces of life may be found.
Bolden has previously said that landing on Mars is essential to ensure the survival of our species.
Addressing the Royal Aeronautical Society in London, in 2014, he said: 'Getting to Mars is important because it is the only planet in the solar system [other than Earth] that we believe might have born life in some form at some time.
'It may be able to sustain life right now, and it definitely can sustain human life if we put humans there.
'That's important for the preservation of the species, and I want to make sure that my grand-daughters, and great-great-granddaughters, have the opportunity to go there.'
Nasa is building a next generation rocket, the Space Launch System (SLS) to take astronauts into deep space in an Orion capsule, to one day potentially land on Mars
Bolden said: 'The SLS and Orion, that's going to be our deep space vehicle to carry our astronauts back into the area around the moon and eventually on to Mars.'
Last month, he told Congress that nuclear thermal propulsion is the 'the most effective' way of sending humans to Mars.
'We are on a journey to Mars and most people believe that, in the end, nuclear thermal propulsion will be the most effective form of propulsion to get there,' he said.
He didn't, however, expand on details on how quickly Nasa hoped the technology could get astronauts to Mars.
Nasa is betting on nuclear propulsion because it weighs almost half as much as a chemical rocket without reducing thrust.
This means larger payloads of cargo can be carried on the spacecraft and they can also be made to travel far faster.
And unlike existing technology, which uses defined trajectories, a nuclear engine also allows a spacecraft to manoeuvre throughout flight.
Nasa's announcement followed news that Russia plans to test a nuclear engine in 2018.
It said the technology could help cosmonauts reach Mars in just six weeks.
This compares to the 18 months spacecraft currently need to get to Mars and could make Russia the first nation to put humans on the red planet.
The $274 million (£192 million) project, which was originally overseen by the space agency RosCosmos in 2010, has now become the responsibility of nuclear group, Rosatom.
'Today's engines can only reach Mars in a year and a half, without the possibility of return.'
Russia currently has used over 30 fission reactors in space, the US has flown only one - the SNAP-10A (System for Nuclear Auxiliary Power) in 1965.
Engineers at Nasa have also been drawing up plans to use nuclear thermal propulsion in a mission to Mars in 2033.
According to the space agency's design, uranium-235 nuclear reactions could be used to heat liquid hydrogen inside a reactor, turning it into ionized hydrogen gas, or plasma.
This plasma is then channeled through a rocket nozzle to generate thrust.
Dr Stanely Borowski, an engineer at Nasa's John Glenn Research Centre, last year outlined how this could then be used to propel a space with its crew through space in a official Nasa paper.
He said the spacecraft, called Copernicus, would consist of separate cargo and crewed transfer vehicles, each powered by a nuclear thermal propulsion stage.
These would be constructed from a 'core' that use three engines each capable of producing thrust of around 25,000 lbs of force.
He estimated that these vehicles could make the 40 million mile (64 million km) trip to Mars within 100 days.
It took the Mars Science Laboratory spacecraft carrying Nasa's Curiosity Rover to Mars 253 days to reach the red planet.
Dr Borowski wrote in his paper: 'The analysis presented here indicates transit time reductions as much as 50 per cent are possible.'
Nasa first began researching nuclear thermal rockets as part of its Nuclear Engine for Rocket Vehicle Application (NERVA) programme in 1959.
However, the project, which was a collaboration between Nasa and the US Atomic Energy Commission, was officially ended in 1973.
During that time, engineers produced several prototypes, the most advanced of which was known as a Pewee engine. None of the engines were ever used for flight.
Proposals to use nuclear powered rockets were also discussed in a presentation last year by Dr Michael Houts, nuclear research manager at Nasa's Marshall Space Flight Centre.
He described the nuclear propulsion was a 'game changing technology for space exploration'.
He said they hoped to prove the viability and affordability of the technology within the next three years.
Dr Houts said: 'Nuclear thermal propulsion is a fundamentally new capability - the energy comes from fission not chemical reactions.
'Advanced nuclear propulsion systems could have extremely high performance and unique capabilities.'