Once every 53 days, Jupiter pulls Juno close.
Locked in orbit since July 2016, the spacecraft has
made five close flybys of the planet so far. It takes
Juno only two hours to zip from pole to pole — a
mad, north-to-south trek shown here in a sequence
of 14 enhanced-color images (left) taken May 19.
As Juno zooms closer, to about 3,400 kilometers
above the cloud tops, new details of Jupiter emerge.
Turbulent clouds signal massive equatorial tem-
pests (inset, top). New Juno data reveal that near
the equator, ammonia rises from unexpectedly
deep in the atmosphere (see Page 14). The upwell-
ing might fuel such storms, but it’s too early to tell.
And what look like white freckles across the south
tropical zone (inset, bottom) are 50-kilometer-
wide cloud towers probably made of ice crystals.
“It’s snowing on Jupiter, and we’re seeing how
it works,” said Juno mission leader Scott Bolton of
the Southwest Research Institute in San Antonio
in a May 25 news conference. Or “it could be hail,”
he added. But it’s not the snow or hail we know; the
precipitation is probably mostly ammonia ice and,
perhaps, some water ice.
Juno doesn’t have eyes only for Jupiter. On its
initial science flyby last August, Juno captured the
first image of Jupiter’s main ring seen from the
inside looking out (above). In the background of
the newly released image, parts of the constellation
Orion wink from afar. These rendezvous won’t go
on forever but could last till 2019. — Emily De Marco
A recurring rendezvous