The solar organization ’s largest moonshine has put on some weight unit around its middle , host a bulge that abide out from the otherwise clean matte aerofoil . The reason is unknown , but one theory hint at exciting development beneath .
Presentingat the recent Lunar and Planetary Science Conference , Dr. Paul Schenk of the Lunar and Planetary Institute compare Ganymede ’s redundant tire to Europa ’s “ craw circles . ”
The bulge is about 3 kilometre ( 2 miles ) high , an unspectacular aloofness on Earth , but a significant feature on a world with a radius two - fifth that of Earth and a loosely flat topography . The prominence is about 600 kilometers ( 375 miles ) across .
“ I found it a bit by fortuity while I was look to complete the global mapping of Ganymede , ” Schenktold National Geographic . He was looking to see if Ganymede had anything similar to the depressions take in on Europa .
Schenk indite , “ Concentricarcuate(curved ) trough - like depressions roughly 25 - 40 km ( 15 - 25 miles ) across and 500 or more kilometer ( 310 miles ) long have previously been key out on Europa . ”
These bowl extend to 1.5 km thick , a huge amount for thenotoriously smoothEuropa ; they form two structures — dub " crop rophy " by planetary scientists — located 10 ° northward and south of the Europan equator , on rough opposite position of the planet .
These trough attain 1.5 kilometer ( 0.9 Admiralty mile ) deep , a vast amount for thenotoriously smoothEuropa . These troughs imprint two structures compared to crop roundabout located 10 ° north and south of the Europan equator , on about diametric side of the planet . They are thought to be a Cartesian product of the strain on Europa ’s ice shell from its rotation .
Credit : Schenk et al . Image ( left ) and topographic mathematical function ( right ) for Europa ’s trough ( T ) and depressions ( S ) .
While nothing standardised was detectable on Ganymede , the bulge could be just as significant . Ganymede ’s surface is amix of rock and ice , but the bulge is thought to be thick ice .
Schenk ’s theory is that the bulge originally grew at either the north or south pole . “ The only place you may get a heavy mass like that — that ’s not related to geology that we know of — is at the cold poles , ” Schenk allege . “ The poles are permanently frigid , so it run to a significant amount of thickening of the crank shell . ”
Ganymede ’s rotation and interaction with Jupiter ’s soberness tugged the superfluous good deal towards the equator . For such an epic journeying to take billet , however , it would require an almost complete lack of friction . This is what one would expect if Ganymede has an internal ocean , asrecent enquiry has suggested . Indeed , it may even havemore than one .
If this theory is correct , Schenk expects a twin hump on the other side of the moon , but the Galileo investigation has not mapped Ganymede in sufficient detail to observe it .
Schenk ’s co - author Bill McKinnon of Washington University , St. Louis , says even if the bulge ’s line of descent are known , it remains a mystery how the bulge is supported , rather than crumble under its own weight . McKinnon noted , “ We ’ve never get wind anything like it before ; we do n’t sleep with what it is . ”
Therefore , the conflict of the bulge is not yet over , as more research is needed to determine the cause of Ganymede ’s waistline bulge .
