Two giant
plumes erupted recently on Jupiter, moving faster than any other Jovian feature
and leaving global streaks of red cloud particles in their wake.
New analyses
of the March 2007 outbursts suggest internal heat plays a significant role in
generating such weather patterns.
The
results, detailed in the Jan. 24 issue of the journal Nature, shed light
on the inner workings of Jupiter's
weather. Planetary scientists and meteorologists have puzzled over whether
internal heat or sunlight (or both) powers Jupiter's stormy disturbances and
jets.
Similar
phenomena occurred in 1975 and 1990, but the most recent event has never been
observed before with high-resolution modern telescopes.
Jovian
outbursts
A team of
astronomers monitored the development of the cloud activity in March 2007 using
NASA's Hubble Space Telescope, the NASA Infrared Telescope Facility in Hawaii
and telescopes in Spain's Canary Islands.
The two
plumes erupted at middle northern latitudes, about 39,150 miles (63,000
kilometers) away from each other and raced across the planet at more than 375 mph
(600 kph). The astronomers watched as each of the plumes mushroomed from its initial diameter
to a whopping 1,245 miles (2,000 kilometers) in about a day.
Slower
moving dark patches and bright features were shed in the wake of the plumes. In
particular, the systems left behind a turbulent planetary-scale disturbance
containing red cloud particles.
The chemical makeup and formation of these red aerosols is a bit of a mystery itself.
"Nobody knows what its composition is," said lead study author Agustin Sanchez-Lavega
of Universidad del Pais Vasco in Spain, "although in the Jovian atmosphere
it is seen in the Great Red Spot and other smaller vortices," he told SPACE.com.
Considered
the most powerful storm on Jupiter
and perhaps in the entire solar system, the Great Red Spot spans twice as wide
as our planet and is at least 300 years old.
Weather
maker
Using their
observations and computer models, the astronomers found the bright plumes
formed in Jupiter's deep water clouds and then shot ice particles and water
well above the visible clouds.
"The
infrared images distinguish the plumes from lower-altitude clouds and show that
the plumes are lofting ice particles higher than anyplace else on the
planet," said study researcher Glenn Orton of NASA's Jet Propulsion
Laboratory in Pasadena, Calif.
The
researchers also found that despite the turmoil created as the plumes churned
through the jet stream, once the plumes waned, the planet's jet stream remained
nearly unchanged. This observation, along with computer models, suggests the
jet stream extends more than 62 miles (100 kilometers) below the cloud tops
where most sunlight gets absorbed.
Since
sunlight is minimal there, the researchers say the results support the idea
that Jupiter's jets are powered by internal heat. This hypothesis was first
proposed based on 1995 observations made when the Galileo probe descended
through Jupiter's
upper atmosphere.
That's
unlike what happens on Earth, where sunlight drives all weather. But for the
outer planets, where the sun's reach can be minimal, a planet's internal heat
might play a substantial role. At the extreme, distant Neptune releases twice
as much heat as it takes in from sunlight, and it boasts winds reaching 1,500 mph
(about 2,400 kph). The release of heat is part of the natural cooling of a
planet, a process that begins at birth when a planet is at its hottest.
"All the
evidence points to a deep extent for Jupiter's jets and suggest that the
internal heat power source plays a significant role in generating the
jet," Sanchez-Lavega said.
The
astronomers found striking similarities between the March event and the two
previous eruptions in 1975 and 1990. All three eruptions occurred with a
periodic interval of about 15 to 17 years. In all three events, the plumes
always appeared in the jet peak and moved at the same speed. In addition, the
disturbances erupted with exactly two plumes each time.
Scientists
say the Jovian findings could have implications for understanding weather on
Earth, where storms are also frequent and jet streams determine large-scale
wind patterns.
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