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.
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.
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 the atmosphere (130 miles (200 km)) melted and vaporized, where pressure crushed it 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, which change in minutes.
We do, however, "see storms appear and disappear on Jupiter," e-mails 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."
Jupiter's rings, how many? WonderQuest
How a moon of Jupiter measures light speed, WonderQuest
Jupiter, Royal Observatory Greenwich
The journey to Jupiter, NASA
Astronomy, Facts on File, edited by Valerie Illingworth
Q: Where did the word 'grapefruit' come from?Debra, Deer Park, Washington, USA
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.
Grapefruit, Cornell University
The seventh wonder of Barbados: grapefruit, Barbados.org
After six years of WonderQuesting with USA TODAY readers, this is my last column for USA TODAY. I hope you will join me for future quests at my website, www.WonderQuest.com, http://www.wonderquest.com/index.htm.
A final word: I'd like to reassure readers who worried about "Making black holes in the lab" (the columns for the last three weeks). A micro black hole can't destroy Earth.
The biggest black hole we can possibly create is a tiny mass (about 25 trillion-trillionths of a kilogram, which is 55 trillion-trillionths of a pound). Moreover, it only lives for about 10^-27 seconds. Then it's gone! Evaporated, as Stephen Hawking predicted. But suppose Hawking's prediction is wrong, and the black hole lives longer. Is Earth in danger?
A micro black hole could pass through a solid iron bar stretched from Earth to the Moon and not hit anything, says physicist Greg Landsberg, professor at Brown University. Moreover, it would take 100 hours for it to encounter and swallow a single proton. In fact, it would take much longer than the age of the universe to destroy "even one milligram of Earth material," says Landsberg. So, a micro black hole cannot destroy Earth no matter how long it lives.
April Holladay, science journalist for USATODAY.com, lives in Albuquerque, New Mexico. A few years ago Holladay retired early from computer engineering to canoe the flood-swollen Mackenzie, Canada's largest river. To read April's past WonderQuest columns, please check out her site. If you have a question for April, visit this informational page.
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