FORBES - Mars remains a true puzzle, but not for the reasons most people would think. Sure, there's debate over whether it ever had surface water, oceans and life. But Mars’ small mass relative to earth and Venus have been a major conundrum that has plagued planetary scientists for decades.
Because the red planet’s mass is roughly only a tenth that of earth, it prompted Carnegie Institution planetary scientist George Wetherill to dub it the ‘small Mars’ problem. There have been several hypotheses to try and explain why Mars ended up so much smaller than earth and Venus. But when hard pressed, few planetary scientists are willing to go to the mat for any of them.
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It certainly is a primary factor, along with its distance from the Sun, Stephen Kane, a planetary geophysicist at the University of California in Riverside, told me via email. Mars’ small size severely limited both the longevity of its geological and volcanic activity that replenished the atmosphere, he said. Its small mass also made it susceptible to being stripped of its atmosphere by the solar wind, said Kane.