How to put a human on MarsContinue reading the main story
56 million km
One of Earth's closest neighbours, Mars is still some 56 million km away at its closest alignment, a journey of at least nine months. Rovers have landed on the Red Planet, probes have scanned its surface but what would it take to put a human on Mars? The BBC asked scientists from Imperial College London to design a mission which could take astronauts to the planet - and back. Watch the videos and explore this interactive to find out about their radical solution.
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The spacecraftClick on labels to explore
The crew would need protecting from the rigours of a nine month journey. Long periods of weightlessness cause bone loss and muscle wastage so the craft is designed to create its own artificial gravity by spinning through space. Shields would lessen, but could not eliminate, the threat of solar and cosmic radiation.
At take-off, the crew are in the lander vehicle but once in Earth orbit they would move into the cruise vehicle. The two vehicles would then separate, remaining joined by a steel cable. Short thruster bursts from both vehicles would send the craft spinning head over heels, creating artificial gravity similar to that on Earth.
The tether is a 60-metre steel cable which attaches the cruise and lander vehicles, allowing them to rotate around an axis. In the event of a major solar flare, the crew would wind in the tether and point the lander's heat shield towards the Sun to protect themselves from as much radiation as possible in the cruise vehicle.
Once the craft reaches Martian orbit, the two vehicles would rejoin and the crew would move back into the lander. This would then descend to the surface of Mars, using the heat shield to moderate its speed and prevent burn-up. Parachutes would deploy to further slow the lander and thrusters would guide it down.
Surviving the trip
During the journey, the crew's health would be monitored closely with wireless sensors but they will rely entirely on medication aboard the craft and the skills of their fellow crew should they fall sick. The long journey and confined quarters could also affect their mental health and conflicts between crew members could arise. Lack of daylight can disrupt sleep patterns, potentially causing poor concentration. Solar and cosmic radiation are constant threats.
After nine long months in space, the crew would guide the lander vehicle down to the Martian surface, making a fairly conventional landing for such an exceptional voyage. The words spoken as the crew become the first humans to ever set foot on another planet would take between three and 20 minutes to travel back to Earth.
The scientists propose a landing spot near the Martian equator where conditions are relatively mild at an average of -30 degrees Celsius, similar to an Antarctic winter on Earth. The crew would live in a habitat sent ahead in an unmanned mission.
While on the planet, the astronauts would conduct extensive geological and atmospheric surveys. They would also drill into the crust, looking for evidence that simple life once existed on Mars. The length of their stay could be as little as three months or as long as two years, governed by the alignment of Earth and Mars.
It would be expensive to send a craft to Mars with enough fuel for a round trip. So a return vehicle would be sent in advance of the manned mission, landing at a latitude where ice exists just beneath the surface. A robotic device would mine the ice and split it into hydrogen and oxygen using electrolysis. This would be used to create methane to power the return vehicle into Martian orbit where it would dock with the cruise vehicle for the long journey back to Earth.
Produced by: Steven Atherton, Neil Bowdler, Christine Jeavans, Salim Qurashi, George Spencer and Tian Yuan.
Mars surface image courtesy of NASA Planetary Data System. Music by Spiro