JUNOCAM a cam­era for the public

JunoCam has made it pos­si­ble for am­a­teur as­tronomers to take their own pho­tos of Jupiter

Sky at Night Magazine - - THE JUNO MISSION -

Of all Juno’s eight science in­stru­ments, the one that has un­doubt­edly cap­tured the public’s imag­i­na­tion like no other is JunoCam.

This vis­i­ble-light cam­era, with a 58° field of view, was in­tended to fa­cil­i­tate un­prece­dented ed­u­ca­tional out­reach and NASA has in­vited ‘cit­i­zen sci­en­tists’ to select re­gions to pho­to­graph dur­ing each per­i­jove pas­sage. Tele­scope ob­ser­va­tions by ground-based as­tronomers and an abil­ity to plot at­mo­spheric fea­tures di­rectly onto the mis­sion’s web­site have en­abled Jupiter to be im­aged by mem­bers of the public at res­o­lu­tions as fine as 2.9km per pixel.

De­scribed as “the public’s cam­era” and “science in a fish­bowl”, JunoCam has pro­duced stun­ningly sur­real im­agery of the So­lar Sys­tem’s largest planet. Colouren­hanced views have pre­sented Jupiter in vivid blues, reds, creams and browns and tracked swirling, con­tort­ing storms, spots and ed­dies, whilst artists and graphic de­sign­ers have also been in­spired to ap­ply their craft to the be­wil­der­ing per­spec­tives.

Mik Pet­ter used math­e­mat­i­cal for­mu­lae to dig­i­tally re-imag­ine the Great Red Spot as some­thing akin to a petri dish, over­crowded with colourised micro­organ­isms, whilst David Englund cre­ated a com­po­si­tion of which French im­pres­sion­ist Monet would have been proud. Oth­ers have in­tro­duced an el­e­ment of fun. One view, cap­tured in May 2017, was dubbed ‘Jovey McJupiterFace’ by cit­i­zen sci­en­tist Ja­son Ma­jor, on ac­count of its spooky sim­i­lar­ity to a hu­man face, com­plete with two rag­ing storms in place of eye­balls.

and with their spi­ral arms fre­quently touch­ing, they re­tain dis­tinct, in­di­vid­ual mor­pholo­gies. At high north­ern lat­i­tudes, Juno also mea­sured the Lit­tle Red Spot – the planet’s third-big­gest an­ti­cy­clone – at half the size of Earth, whilst at 40° south it re­vealed the ‘string of pearls’, a chain of oval-shaped, coun­ter­clock­wise-re­volv­ing storms.

Juno has sam­pled ther­mal mi­crowave ra­di­a­tion from the at­mos­phere, re­veal­ing the equa­to­rial belts pen­e­trate deep in­side the planet. So too do at­mo­spheric winds, which en­dure far longer than sim­i­lar pro­cesses on Earth. Con­trast­ingly, high­er­lat­i­tude belts and zones evolve into other struc­tures, in­di­cat­ing vari­able am­mo­nia con­cen­tra­tions. Wa­ter, al­though iden­ti­fied by ear­lier mis­sions, re­mains sur­pris­ingly elu­sive. In Oc­to­ber 2017, clouds of am­mo­nia ice and pos­si­bly wa­ter were found. By mea­sur­ing the oxy­gen-hy­dro­gen ra­tio and wa­ter bal­ance, the­o­ries on how Jupiter formed can be con­fi­dently ad­dressed.

Grav­ity’s re­gional vari­a­tions

Grav­i­ta­tional ob­ser­va­tions, pub­lished in March 2018, in­di­cate strik­ing north-south asym­me­tries, not dis­sim­i­lar to that seen in the belts and zones. This arises from gaseous flows deep within the planet and Juno showed that the vis­i­ble east­ward and west­ward jet streams also ex­hibit north-south asym­me­try. The mag­ni­tude of this asym­me­try al­lows the jets’ depth to be de­ter­mined. Re­mark­ably,

“Mi­crowave ra­diom­e­try re­vealed that the Great Red Spot’s roots plunge up to 100 times deeper than our oceans”

Jupiter’s 3,000km-deep weather layer com­prises one per cent of the planet’s en­tire mass, com­pared to 0.000001 per cent in the case of Earth. And in one of the great­est sur­prises of the mis­sion, this gaseous world ro­tates al­most as a rigid body be­neath its mas­sive weather layer.

In July 2017, the space­craft hur­tled 9,000km over the fa­mous Great Red Spot. This cen­turies-old storm has mor­phed in shape and di­min­ished in size over time, to­day mea­sur­ing 16,350km across – 1.3 times larger than Earth – and Juno de­tected a tan­gle of dark, veiny clouds weav­ing through it. Mi­crowave ra­diom­e­try re­vealed that its roots plunge to a depth of 300km, which is some 50-100 times deeper than our oceans.

For now, the fu­ture for this mis­sion re­mains un­cer­tain be­yond July 2018, as Juno awaits its fate. Yet in two years it has rev­o­lu­tionised hu­man­ity’s un­der­stand­ing of a world 1,300 times big­ger than our own. “We knew that Jupiter would throw us some curves,” says Bolton. “We didn’t ex­pect that we would have to take a step back and be­gin to re­think this as a whole new Jupiter.”

David Englund’s avant-garde work rein­ter­prets the Great Red Spot in the style of Claude Monet

Eco artist Mik Pet­ter gives the Jo­vian land­scape a colour­ful frac­tal makeover

It’s not just Mars that has peo­ple see­ing ghostly faces. Meet Jovey McJupiterFace

Juno re­vealed that be­neath Jupiter’s writhing bands, its gas core acts like a rigid body

The Lit­tle Red Spot, a storm on the edge of Jupiter’s north­ern po­lar re­gion

A JunoCam view of Jupiter’s String of Pearls: ac­tu­ally vast, swirling storms

Sci­en­tists be­lieve that the brighter clouds in this im­age are up­drafts of am­mo­nia ice crys­tals pos­si­bly mixed with wa­ter ice

An en­hanced-colour im­age of Jupiter’s Great Red Spot which was cre­ated by cit­i­zen sci­en­tist Kevin Gill

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