At last count , Jupiter had92 moon , so it can be tough to get the spotlight . particularly when you are contend with the the like of Europa , bear witness off with trace of secret oceans , and possibly have off massiveplumes of water .
Callisto , despite being the second - largest of Jupiter ’s absurd number of Moon and the third - with child synodic month in the Solar System , does n’t get a whole lot of attention . The frigid lunation has theoldest surfacein the Solar System , and may have an sea deep below the thick crust , but has failed to gain the scientific pursuit and ensue NASA missions of the other large moons .
However , it can still throw some surprises our way . The latest is that it has a lot more O than we were expecting . We were expecting to come up a little oxygen , after NASA probe Pioneer 10 found vivid plasma in Jupiter ’s magnetosphere . experimentation were convey to watch the event this plasma had on icy moons Europa , Ganymede , and Callisto .
" These experiments measured the exclusion of weewee molecules from small - temperature ice by incident saddle speck , a process name to as sputtering , " a team of research worker write in a new study . " The results showed that the sputtering of H2O - ice rink is dominated by electronic excitement and ionisation produce in the ice ( electronic sputtering ) , rather than by rap - on hit of the ion with water molecules ( atomic sputtering ) , the hitherto typically studied struggle process . "
" Subsequent experimentation led to the find that the bonds in H2O - ice corpuscle can be dissociated by the electronic energy deposited by the encroach charged particle , and the fragmented molecules can recombine to spring new species , such as H2and O2 . "
These model made us expect to find oxygen , but we did n’t have a go at it how much . set about to quantify how much atmospheric oxygen this would produce on Callisto , the squad found that it fall far short of the amount of oxygen we believe is there from our observations .
" There ’s a immense discrepancy , " pass author Shane Carberry Mogan toldCNET . " We were off by something like two ordering of order of magnitude to even three orders of order of magnitude . "
Even if the moon was 100 percent cover in ice , rather than the 10 percent assumed by the squad , it still would n’t account for all the atomic number 8 produced . The team suggested a number of other mechanisms by which this surplus oxygen is make its way into the aura , include a series of chemical reaction in water vapor and oxygen ion nidation from Jupiter ’s magnetosphere , but neither would produce nearly enough oxygen to explain observations either .
The team propose watching , perhaps during the upcomingJUICE missionto vanish by the glacial moon of Jupiter , should attempt to obtain " multi - point , concurrent measurements of the moon ’s charge and achromatic particle environments " in ordering to help oneself work the secret .
The subject is published inJGR Planets .
