Adelaide-born NASA astronaut Andy Thomas. And all agreed humankind would eventually be on Mars, with regular flights between Earth and the red planet, largely because of the strong interest shown by private entrepreneurs such as Elon Musk and his SpaceX. Musk believes he can land small parties on Mars by the mid 2020s. Aerospace engineer Dr Thomas, Australia's first astronaut in space, said humans would make permanent bases on Mars within 50 years. "We will have colonies on Mars," he said.

Thomas flew in the Space Shuttle Endeavour in 1996, then spent 141 days in space in the Mir space station, before making his final space trip in the 2001 Space Shuttle Discovery to the International Space Station, where he completed a 6½ hour space walk. But he said humans should never view Mars as a back-up option for Earth. “Mars is a harsh environment," the NASA astronaut told the audience of We Will be Martians: Our Future on the Red Planet, hosted by moderator Professor Brian Greene. "It will never be a second Earth,” he said. He said Mars did not give mankind the opportunity to forget about problems on Earth and concentrate solely on a new settlement on Mars.

“I think that is arrogant hubris," he said. The session tackled the different aspects of a simulated flight to Mars, including the journey itself and the varying ways in which a spacecraft could return, before the audience looked at Martian craters and crevasses - some five kilometres deep - through 3D glasses. Geologist Dr Jon Clarke works at simulated Martian camps in the deserts of Utah and the freezing conditions of the Antarctic. Professor Clarke and Professor Charles spoke about how the shortest trip to Mars could take "three to four months" if electric power was used, but conventional wisdom was for a 16-month round trip. “You need to have a lot of fuel to get off the Earth’s surface and get into space,” Professor Charles said, adding that future trips might not use conventional rocket flight.

One option being explored was a 36,000-kilometre space elevator to take crews to a lift-off station which would not need as much fuel to leave the Earth's atmosphere. Sand dunes on Mars. “At the moment the big problem is the tether," she said. "How do you build something that is 36,000 kilometres long." The concept was already being tested with small prototypes, she said.

Loading "We are (also) testing the concept of one of these electric (plasma propulsion) engines with one of these nano-satellites,” she said. “The fact that the private sector is involved in this, I really think it has a chance of getting ahead." Dr Thomas said he thought that method could work "into the future" but more sophisticated conventional rocket launch propulsion would get the first humans to Mars. But science could develop the type of hydrogen fuel that could be used to return from Mars.

“We do know on the surface of the Moon in some deep craters there is crater ice,” he said. “We can break it down and make hydrogen and oxygen, which we can use to breathe and in fuels." Professor Greene said sending teams with robots was significantly cheaper than sending space teams with humans. "We can launch 1000 robots for the same cost as you can for two astronauts," Professor Greene asked. "Why not send robots?"

Loading But Professor Cagle said robots - even with advances in artificial intelligence - did not have the ability to work towards an objective. "Robots do not have curiosity," she said. "That is what you have with humans.” Professor Reynolds noted that tackling boredom on long space flights was an important part of making any mission to Mars successful.