The incredible mass of
Jupiter helped shape our little corner of the universe, and hidden in its
swirling clouds could be the answers to a great many questions scientists still
have about the early solar system. NASA’s Juno spacecraft was launched five
years ago to tease out some of those secrets, and it’s going to arrive at
Jupiter in just a few weeks. It will get closer to the planet than any of the
eight past robotic missions, allowing us to finally peer beneath the clouds.
Juno was launched in the Summer of 2011, heading out on an
eccentric path that took it past the orbit of Mars. That was just to prepare it
for a gravity assist from Earth that took place in 2013. This set Juno on the
necessary trajectory for its Jupiter encounter in several weeks. NASA is
expecting Juno to enter orbit of the massive planet on July 4th, at which
time it will take up a polar orbit. This is the preferred way to survey a
planet because it’s perpendicular to the angle of rotation.
NASA hopes to see Juno complete 37 orbits of Jupiter over
the course of 20 months. Most of those will be 14-day orbits, but the first few
will be longer as the probe uses its small hydrazine engine to nudge it into the
proper position. The orbital path chosen byNASA will put Juno within
3,000 miles of Jupiter’s cloudtops, far closer than any probe has gotten. This
is risky because Jupiter blasts out a huge amount of radiation that can fry a
spacecraft that was not specifically designed to cope with it. On Earth we have
a background radiation level of about one-third of a rad. Juno will be exposed
to more than 20 million rads over the course of its Jupiter study.
Despite the ease with which even backyard amateur astronomers
can peek at Jupiter’s massive form, we don’t know exactly what it’s like
inside. Scientists think that when Jupiter formed, it vacuumed up all the gas
nearby. That gas is what makes up most of Jupiter to this day. It’s a sample of
the matter that formed our entire solar system, just waiting to be analyzed.
One of the big questions Juno could answer with its microwave radiometer is how
much water is in Jupiter’s atmosphere. That could tell researchers where
Jupiter formed and what the environment was like when it did.
Water isn’t the whole story, though. Juno may also answer
once and for all the question of whether or not Jupiter has a solid core. Juno
carries a radio wave instrument that is capable of measuring Jupiter’s gravity
as the spacecraft is jostled during its approaches. This should allow
researchers to map the distribution of mass inside Jupiter and figure
out if the core is solid or flowing.
Juno has cameras as well, so expect to see some fantastic
images of Jupiter in the next few months as the probe settles in to do some
science
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