Auroras
The presence of an atmosphere
allows many comparisons. Earth,
Mars, Jupiter, Saturn, Uranus
and Neptune all exhibit auroras.
Most auroras are a result of the
interaction of the solar wind with
a planet’s magnetic field. The
exception is Mars because it lacks
a field. The magnetic field provides
a pathway for solar wind particles
to enter the planet’s atmosphere
near the planet’s magnetic poles.
The auroral oval structure is
common. The direct collision of
the solar wind at the top of the
Martian atmosphere leads to
auroral glow that is much less
defined over Mars. These images
show the auroral ovals of Earth,
Jupiter and Saturn.
Storms
Earth
COURTESY OF NASA / UC Berkeley
Earth
COURTESY OF NASA
Jupiter
COURTESY OF NASA/JPL
Storms are seen around the
Solar System — on every planet
and satellite with a substantial
atmosphere. Surface wetting
and flooding from rain is familiar
on Earth and also seen on Titan.
Convection storms, some including
lightning, are seen on Earth,
Jupiter, Saturn and Titan. Cyclonic
storms are observed on Earth,
Mars, Jupiter, Saturn and Neptune.
Spiraling cyclones are found
throughout the Solar System.
Mars
Saturn
COURTESY OF ESA/Hubble
Jupiter
COURTESY OF NASA/ESA, and John Clarke (Boston University)
Atmospheric circulation
George Hadley published a theory
explaining the circulation of Earth’s
atmosphere in 1735. He suggested
that convection cells spanning from
Earth’s equatorial zone to its poles
carried heat to higher latitudes. Now
called Hadley cells, this circulation
would make the poles warmer and
cool the temperate latitudes as the
air flowed back to the equator. It
turned out that he oversimplified
Earth’s circulation pattern (there
COURTESY OF ESA, Venus Express, VIRTIS, INAF-IASF, Obs. de Paris-LESIA
are two large convection
patterns and plenty of
complications as well in
each hemisphere) but he
got it right for Venus.
Atmospheric circulation
can get interesting at
planetary geographic
poles. A polar vortex on
Earth plays a role in the
Antarctic ozone hole, that
is now repairing itself
thanks to the withdrawal
of chlorofluorocarbons
COURTESY OF NOAA Climate.gov
(CFCs) from production
and dispersal. But our spacecraft have shown us very interesting polar vortices
around the Solar System. Clockwise from top left, the polar vortices on Venus,
Titan, Saturn and Earth are similar phenomena but exhibit very different
appearances.
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Neptune
COURTESY OF NASA/JPL
Saturn
COURTESY OF NASA/JPL
COURTESY OF NASA
Dust Storms /
Dust Devils
Titan
COURTESY OF NASA/JPL-Caltech/SSI
Saturn
COURTESY OF NASA/JPL-Caltech/SSI
Sky’s
Up
Wind carries dust on planets and
satellites with atmospheres and hard
surfaces. While Mars can suffer planetwide dust storms (one of which was
under way when NASA’s Mariner 9
arrived at the planet in 1971), smaller
dust storms there are more common
and frequent, and they can look eerily
familiar. We also see local effects that
combine to make familiar dust devils
in unfamiliar places. A dust storm on
Mars (top right) shows flow very similar
to dust blowing off the Sahara over the
Atlantic Ocean (top left). Dust devils
on Earth and on Mars can extend high
into the atmosphere and track across
the ground for long distances. No one
knows if Titan has dust devils. They
cannot be seen easily from above
through its hazy atmosphere.
Sky’s
Up
Earth
COURTESY OF NASA/GSFC
Earth
COURTESY OF NASA/JPL
Mars
COURTESY OF NASA/JPL/Malin Space Science Systems/MGS
Mars
COURTESY OF NASA/JPL-Caltech/University of Arizona
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