ScotRafkinandTimothyMichaelsdevelopedamodelofthisstructurebasedonRAMS.TheHesperianPeriod saw an injection of hydrogen sulfide (^)  
ScotRafkinandTimothyMichaelsdevelopedamodelofthisstructurebasedonRAMS.TheHesperianPeriod saw an injection of hydrogen sulfide (^)  into this structure, where an increase in methane was measured in 2014. Its composition has seasonal variations due to sublimation (+)  of polar ice caps, and cirrus clouds were observed here in 2004 by  Opportunity.  The pressure due to this structure measures 30 pascals (*)  at the peak of Olympus Mons. Consisting of 96% carbon dioxide is Â– for ten points Â– what envelope of gases surrounds the fourth planet from the Sun?
ScotRafkinandTimothyMichaelsdevelopedamodelofthisstructurebasedonRAMS.TheHesperianPeriod saw an injection of hydrogen sulfide (^)  
atmosphere  of  Mars  (accept equivalents; prompt on "Mars" but not on just "atmosphere")