Recent observations confirm that the Great Red Spot now is approximately 10,250 miles across!
Jupiter’s trademark Great Red Spot — a swirling anti-cyclonic storm
larger than Earth — has shrunk to its smallest size ever measured.
According to Amy Simon of NASA’s Goddard Space Flight Center in
Greenbelt, Maryland, recent NASA Hubble Space Telescope observations
confirm that the Great Red Spot now is approximately 10,250 miles
(16,500 kilometers) across. Astronomers have followed this downsizing
since the 1930s.
Historic observations as far back as the late 1800s gauged the storm to
be as large as 25,500 miles (41,000km) on its long axis. NASA Voyager 1
and Voyager 2 flybys of Jupiter in 1979 measured it to be 14,500 miles
(23,300km) across. In 1995, a Hubble photo showed the long axis of the
spot at an estimated 13,020 miles (21,000km) across. And in a 2009
photo, it was measured at 11,130 miles (17,900km) across.
Beginning in 2012, amateur observations revealed a noticeable increase
in the rate at which the spot is shrinking — by 580 miles (930km) per
year — changing the shape of the Great Red Spot from an oval to a
circle.
“In our new observations, it is apparent very small eddies are feeding
into the storm,” said Simon. “We hypothesized these may be responsible
for the accelerated change by altering the internal dynamics and energy
of the Great Red Spot.”
Simon’s team plans to study the motions of the small eddies and the
internal dynamics of the storm to determine whether these eddies can
feed or sap momentum entering the upwelling vortex, resulting in this
yet unexplained shrinkage.
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