By Hampton Sides
Is Pluto really a planet?
— J. Durant, Essex, Maryland
After assiduous campaigning by its discoverers at Arizona's Lowell Observatory, distant Pluto was hastily declared a planet in 1930, and ever since then schoolchildren have been taught with great conviction that there are nine large bodies, or "major planets," revolving around our Sun. Yet if it were discovered today, Pluto would certainly not make the
grade in the majors. For starters, it's too small — less than half the size of Mercury and smaller than our own Moon — and it has no gravitational influence on the orbits of the other eight planets. Brutal as it may seem, Pluto has been demoted, though since the early nineties scientists have been haggling over what diminutive name it deserves:
asteroid, minor body, dwarf planet, or perhaps the ultimate slap, "planetesimal." Whatever Pluto is, it's one of the true enigmas of our solar system, a ball of frozen methane that has an elliptical orbit and behaves rather like a comet. "It's a fascinating minor body," concedes astronomer Daniel Green of the Harvard-Smithsonian Center for Astrophysics,
"but no one seriously calls Pluto a major planet anymore, except for a couple of whiners who're stuck in the 1930s."
Which volcano will be the next to blow its stack?
— Clancy Tristan, Payette, Idaho
Topping volcanologists' A-list Popocatepetl, a 17,887-foot peak that's been spewing ash on Mexico City since 1992. Scientists fear that even a minor eruption would melt the snow on Popo's flanks and create a massive, fast-moving mud surge, known as a lahar, that could overrun the large communities along its drainages. (A lahar from Colombia's Nevado del
Ruiz volcano buried some 23,000 people alive in 1985.) Experts also fear an encore from Italy's legendary Vesuvius, the source of recent rumblings and not a few nights of lost sleep in nearby Naples. Closer to home, the rock interior of Washington's Mount Rainier has been so hollowed out by erosion that a small tremor could cause the steep slopes to cave in
on themselves, unleashing a devastating lahar. Says Ed Klimasauskas, of the U.S. Geological Survey's Cascades Volcano Observatory, "We're worried that Rainier may be rotting from the inside out." Even more worrisome, however, is the ever-energetic Mount St. Helens, whose steam blasts of late have prompted a few bold researchers to predict a major eruption
in 2000. But volcanology is a notoriously inexact science, so don't hold your breath.
Why do fireflies light up
— Courtney Skouteris, Atlanta, Georgia
Fireflies live most of their short lives as larvae, eating like fiends in order to build up energy for sex. Come summertime, the larvae transform into the blinking, winged beetles we know so well. But their days are numbered (to about seven, in fact), and so they spend nearly every minute engaged in a frantic hunt for a mate. Which is where those little
bursts of bioluminescence — caused by a complex chemical reaction involving an enzyme known as luciferase — come in. "It's the way male lightning bugs advertise their services," explains University of Florida entomologist James E. Lloyd, noting that each species has its own signature style, composed of complicated variations of flickers and
pulses. When the waiting female, hunkered safely in the grass or atop a branch, lays her tiny beetle eyes on a particularly enticing sexual semaphore, she flashes a slow, seductive, come-hither signal and mating begins — a feat that can take hours. Could there be a more compelling reason to free them from their mason jars?
|August hosts the annual perseid meteor shower, so named because the meteors appear to radiate from the constellation Perseus. This year doesn't deal Perseid-viewers a good hand, however: The shower begins on the evening of the 12th but peaks early the next morning above the north-northeast horizon, at
which point it will be largely obscured by the glare of the Moon overhead. Telescope buffs take note: August is prime time for viewing Saturn's rings, tilted at a 17-degree angle and thus easily discerned through a small scope. In the final days of the month, all of the naked-eye planets — Venus, Mercury, Mars, Saturn, and Jupiter — will
be visible together in the predawn twilight. August's full Moon occurs on the seventh.
— Jean Quashnock
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