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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. 

Jupiter's 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 Earth’s 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 Earth’s surface pressure.  We don’t 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 — once every 11 hours.”

This just in from NASA (June 29, 2007):

Changes in Jupiter's cloud bands.  Courtesy of NASA's Hubble Space Telescope and Newswise Science News.  Click for larger image.

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.

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Q:  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:  grapefruit.

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.

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(Answered June 25, 2007; Updated June 29, 2007)

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