This graphic shows the flux of radiation detected by NASA's Mars Science Laboratory on the trip from Earth to Mars from December 2011 to July 2012. The spikes in radiation levels occurred in February, March and late May of 2012 because of large solar energetic particle events caused by giant flares on the sun. The data were obtained by the Radiation Assessment Detector on Curiosity. The radiation levels are measured in units of flux or particles per square centimeter per second per steradian. The MSL spacecraft structure (which includes the backshell and heatshield) provides significant shielding from the deep space radiation environment, reducing significantly the particle flux observed by the Radiation Assessment Detector.