Permanent Human Settlement of the Earth, Space and Ocean Frontiers

Tuesday, January 07, 2014

Radiation Exposure on Mars - On the 10th Anniversary of NASA Mars Rovers

     When the NASA Rover Curiosity landed on Mars, it carried with it a radiation meter to assess the dose of ionizing radiation on the surface of the Red Planet.  Since there is so much interest in launching human missions to Mars, the greatest known risk was thought to be radiation exposure from cosmic rays.  Unlike earth, Mars has a fractional atmosphere and equally insignificant natural magnetic shield to buffer and push the high energy – high mass cosmic radiation away from human contact.  But after more than a year on the surface of Mars watching the radiation meter daily – here is what Curiosity has reported – and it is not good news at all for would be Martian explorers:
     The rover discovered that the ‘natural’ background radiation exposure on Mars (almost entirely- 95% - from high energy cosmic rays) was on the order of 0.67 millisieverts per day.  Let me put that in perspective.  On the earth – with its very effective cosmic ray shield of a thick atmosphere and the magnetosphere protects us from this natural cosmic environment endless bombardment of ionizing radiation.  Thus, for the average human at the average spot on earth, we routinely receive on the order of 0.007 millisieverts per day of background radiation – a difference of almost 100 times less!  Here are some other comparisons.  One day on Mars would be the equivalent of receiving 33 chest x-rays per day, or on average, one whole body CAT scan every 5 days.  The Martian astronaut would be receiving 244 times the allowed radiation dose from all nuclear power sources for the public and 60 times the maximum dosage allowed for professional nuclear power plant workers.  And at that rate, the astronaut would be receiving in a single one year nearly twice the current allowable lifetime dose for career NASA astronauts – and the minimal Mars mission is estimated at three years for a cumulative over-dose of six times the current career radiation exposure.  Further – during the time of measurement, the sun was unusually quiet and did not add its typical solar induced dose to the picture, which only inevitably adds to the bleak picture.
     What is the solution?  I believe it is ‘relatively simple’:  increase the transit speed and thereby reduce the transit time and future Martian explorers and settlers will all inevitably live under the Martian surface where they can be effectively and safely shielded from the hazardous environment on the surface.   
PS.  The same is true for lunar explorers as well as practically everywhere outside of low earth orbit.