it is suggested that the mass-2 ion observed by pioneer venus is d ( + ) , which implies a ratio of deuterium to hydrogen in the contemporary atmosphere of about 10 ( -2 ) , an initial ratio of 5 x 10 ( -5 ) and an original h ( 2 ) o abundance not less than 800 grams per square centimeter .
C0020275
hydrogen
C0011744
h ( 2