The wind-swept, misty surface of Jupiter;
the many names of grapefruit
Q: What is the surface like on Jupiter? Sam,
Coon Rapids, Minnesota
A: Jupiter's surface is a sea of yellowish cloud tops that roil with
winds continually circling the great planet. The gales whip around the
equator at double our hurricane speeds (340 mph, 550 km/h).
It's windy here, and cold. The temperature on the surface is about -235
degrees F (-150 C), which is twice as cold as the coldest spot in Antarctica.
colorful cloud bands and Great Red Spot (lower left). Photo courtesy of NASA.
Surface clouds form alternating bands of
color, which speed in opposite directions, like passing trains. Yellow bands
are the tops of great convective bubbles buoyed by a gas and liquid-hydrogen
'soup' heated by Jupiter's 36,000-degree F (20 000 C) core. Reddish brown bands
are lower cloud layers that ride descending convective currents. Yellow-band
clouds blow easterly and red-band ones whip across the planet westerly. Fierce
tornados rage between bands.
The most spectacular
sight on Jupiter's surface is the Great Red Spot, a high-pressure storm
gyrating in the opposite direction from Earthís low-pressure hurricanes.
We Earthlings have watched this long-lasting storm for almost 400 years, since
we invented the telescope in 1608.
Jupiter's interior: The upper gaseous layers (shown as yellow) transition to
liquid hydrogen (aqua) above a thick layer of metallic hydrogen (gray). The
center (brown) may be a solid rocky core. The metallic layer conducts
electricity much like metals, and is responsible for Jupiter's strong (19,000
times stronger than Earth's) magnetic
field. Drawing/photo composite courtesy of R.J. Hall, NASA.
We can't land here on Jupiter's surface,
since it's a sea of cloud tops, but we can get warmer by descending.
Buffeted by extreme winds, we descend, and the pressure mounts. The winds
don't subside. They continue to blow about 450 mph (725 km/h) all the way
down the atmosphere (at least as far as we've probed). Lightning flashes
in the distance, as we dip below the upper cloud base.
The temperature increases
to a balmy 70 degrees F (21 C), as we continue down. Here is where life might
exist, although the pressure is ten times Earthís surface pressure. We donít
want to go down more. In December of 1995, the single probe we sent deeper into
hellish depths (130 miles (200 km)) melted and vaporized, where pressure crushed
with twenty times Earth's surface pressure.
Jupiter's heat is a fossil from 4.6 billion
years ago, when planets coalesced from an ancient cloud of gas and dust. If the
proto-Jupiter had attracted 50 times more mass, then Jupiter's core would have
gone nuclear, and become a star. This many eons later, Jupiter still radiates
twice as much heat as it receives from the Sun.
Moreover, the residual heat apparently fuels
the fierce winds that lash the planet's atmosphere, according to
Jonathan Aurnou, UCLA assistant professor of planetary
physics, who has modeled
convective currents deep within. The
convective currents maintain much the same pattern and, therefore, Jupiter's
cloud patterns stay largely unchanged through the centuries, unlike ours that
change in minutes.
We do, however, "see
storms appear and disappear on Jupiter," emails astronomer
Jim O'Donnell of the Royal Observatory Greenwich in London. "The overall structure of the
dark and light equatorial cloud bands is permanent. Jupiter's rotation, however,
whips them into bands. The same effect creates atmospheric bands on Earth that
move in opposite directions, too. But Jupiter hurls its bands at manic speed
because it is big and rotates much faster ó once every 11 hours.Ē
This just in from NASA (June 29, 2007):
Changes in Jupiter's cloud bands. Courtesy of NASA's Hubble Space
Newswise Science News. Click for
Between March 25 and June 5, Hubble's Wide Field and Planetary Camera 2
captured entire bands of clouds changing color. Zones have darkened into belts
and belts have lightened and transformed into zones. Cloud features have rapidly
altered in shape and size. The image at left shows a thin band of white clouds
above Jupiter's equator. The white color indicates clouds at higher altitudes in
Jupiter's atmosphere. In the image at right, the band's white hue has turned
brown, showing clouds deep within the planet's atmosphere. The whole band
appears to have merged with the one below it.
Jupiter's rings, how many? WonderQuest
How a moon of Jupiter measures light speed,
Jupiter, Royal Observatory Greenwich
Jupiter probe detailed look, NASA
The journey to Jupiter, NASA
Jupiter's massive winds likely generated from deep inside, Space. com
Hubble Catches Jupiter Changing Its Stripes, Newswise science news
Astronomy, Facts on File, edited by Valerie Illingworth
Where did the word 'grapefruit' come from? Debra, Deer
Park, Washington, USA
A grapefruit tree, which, in the USA, only grow in the southern states, and
commercially in Florida, Arizona, Hawaii and California.
Photo courtesy of
photographer G.A. Copper and the US Department of Agriculture
A: Grapefruit grow in bunches, somewhat as grapes do, hence the name:
Until the 1800s, we called grapefruit 'shaddock'; it's a cross between the
pomelo and the sweet orange. Grapefruit were also known as the 'forbidden
fruit of Barbados' (a small island about 300 miles (400 km) northeast of
Venezuela), where we first found them in the 1700's.
(Answered June 25, 2007; Updated June 29, 2007)