Scientists are now counting down to the
moment that NASA spacecraft Juno
arrives at Jupiter late this afternoon (NZT)
, following a five-year trek across the
Solar System.
Juno’s mission: To peer through Jupiter’s
cloud-covered atmosphere and map the
interior from a unique vantage point
above the poles. Among the lingering
questions: How much water exists? Is
there a solid core? Why are Jupiter’s
southern and northern lights the brightest
in the solar system?
At around 3.15pm NZT today, the solar-
powered spacecraft will fire its main
rocket engine to slow itself down from a
speed of 250,000 km/h and slip into orbit
around Jupiter.
The spacecraft is travelling through a
hostile radiation environment and rings of
debris and dust, “making for very serious
hazards,” Juno chief scientist Scott
Bolton said during a briefing.
But Juno should be able to withstand the
harsh conditions because it’s “built like
an armored tank,” he said.
With its billowy clouds and colourful
stripes, Jupiter is an extreme world that
likely formed first, shortly after the sun.
Unlocking its history may hold clues to
understanding how Earth and the rest of
the solar system developed.
“We know much about what it looks like
from the outside, but know almost
nothing about what’s on the inside – only
what’s been inferred by experts,” said Dr
Grant Christie, an astronomer at
Auckland’s Stardome Observatory.
The spacecraft’s camera and other
instruments were switched off for arrival,
so there won’t be any pictures at the
moment it reaches its destination.
Jupiter was been fundamental to the
evolution of our solar system, weighing
twice as much as all of the other planets,
asteroids and comets within it combined.
“It’s probably why we are here,” Dr
Christie said.
The trek to Jupiter, spanning nearly five
years and 2.8 billion km, took Juno on a
tour of the inner solar system followed by
a swing past Earth that catapulted it
beyond the asteroid belt between Mars
and Jupiter.
Along the way, Juno became the first
spacecraft to cruise such a distance while
powered by the sun, beating Europe’s
comet-chasing Rosetta spacecraft.
A trio of massive solar wings sticks out
from Juno like blades from a windmill,
generating 500 watts of power to run its
nine instruments.
Juno, built by Lockheed Martin, is an
armoured spacecraft – its computer and
electronics are locked in a titanium vault
to shield them from harmful radiation.
Even so, Juno is expected to get blasted
with radiation equal to more than 100
million dental X-rays during the mission.
Like Galileo before it, Juno will meet its
demise in 2018 when it deliberately dives
into Jupiter’s atmosphere and
disintegrates – a necessary sacrifice to
prevent any chance of accidentally
crashing into the planet’s potentially
habitable moons.

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