<P> Slightly smaller than Earth 's Moon , Europa is primarily made of silicate rock and has a water - ice crust and probably an iron -- nickel core . It has a tenuous atmosphere composed primarily of oxygen . Its surface is striated by cracks and streaks , whereas craters are relatively rare . In addition to Earth - bound telescope observations , Europa has been examined by a succession of space probe flybys , the first occurring in the early 1970s . </P>
<P> Slightly smaller than Earth 's Moon , Europa is primarily made of silicate rock and has a water - ice crust and probably an iron -- nickel core . It has a tenuous atmosphere composed primarily of oxygen . Its surface is striated by cracks and streaks , whereas craters are relatively rare . In addition to Earth - bound telescope observations , Europa has been examined by a succession of space probe flybys , the first occurring in the early 1970s . </P>
what is the atmosphere of europa made of
what is the atmosphere of europa made of
primarily of oxygen
primarily of oxygen