Cassini’s view of Jupiter’s southern hemisphere
Copyright: NASA/JPL/Space Science Institute
This Cassini image shows Jupiter from an unusual perspective. If you
were to float just beneath the giant planet and look directly up, you
would be greeted with this striking sight: red, bronze and white bands
encircling a hazy south pole. The multicoloured concentric layers are
broken in places by prominent weather systems such as Jupiter’s famous
Great Red Spot, visible towards the upper left, chaotic patches of cloud
and pale white dots. Many of these lighter patches contain
lightning-filled thunderstorms.
Jupiter has very dramatic weather –
the planet’s axis is not as tilted (towards or away from the Sun) as
much as Earth’s so it does not have significant seasonal changes, but it
does have a thick and tumultuous atmosphere filled with raging storms
and chaotic cloud systems.
These clouds, formed from dense layers
of ammonia crystals, are tugged, stretched and tangled together by
Jupiter’s turbulence and strong winds, creating vortices and
hurricane-like storms with wind speeds of up to 360 km per hour.
The
Great Red Spot is actually an anticyclone that has been violently
churning for hundreds of years. It was at one stage large enough to
contain several Earth-sized planets but recent images
from the Hubble Space Telescope show it to be shrinking. There are
other similarly striking storms raging in both Jupiter’s cool upper
atmosphere and hotter lower layers, including a Great Dark Spot and Oval BA, more affectionately nicknamed Red Spot Jr.
Jupiter’s
south pole is at the very centre of this image, visible as a murky
grey-toned circle. This patch is not as detailed as the rest of the
planet because Cassini had to peer through a lot more atmospheric haze
in the polar region, making it harder to see.
This polar map is
composed of 18 colour images taken by the narrow-angle camera on NASA’s
Cassini spacecraft during a flyby on 11–12 December 2000. This map is
incredibly detailed; the smallest visible features in this image are
about 120 km across. There is also an accompanying map of the planet’s north pole. In 2016, NASA’s Juno spacecraft will arrive at Jupiter and start to beam back images of the planet’s poles.
The
Cassini–Huygens mission, launched in 1997 as a joint endeavour of ESA,
NASA and Italy’s ASI space agency, flew past Venus, Earth and Jupiter en
route to observe Saturn, its moons and rings. Observations with Cassini
have given us an unprecedented understanding of the Saturnian system.
ESA’s Juice mission aims to do
the same for Jupiter. Planned for launch in 2022, the spacecraft will
reach Jupiter in 2030 and begin observing the planet and three of its
moons – Ganymede, Callisto and Europa. Previous flybys of these moons
have raised the exciting prospect that some of them might harbour
subsurface liquid oceans and conditions suitable to support some forms
of life.
Juice was recently given the green light to continue to the next stage of development.
Source: ESA
