| Subject: Another near miss may have wiped out life in September |
Author:
Betty
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Date Posted: 16:18:41 05/04/04 Tue
In reply to:
Betty
's message, "Asteroid near miss could have wiped out a city" on 11:36:55 03/19/04 Fri
City-sized asteroid to clear Earth
On Sept. 29, 2004 an asteroid the size of a small city will make the closest known pass of such a very large space rock anytime this century.
However, I'm sure most world governments, & astronomers, to avoid panic (AND because there would be nothing we could do about it except pray any), would not let us know if it were heading towards your town anyway. An asteroid this size would wipe out most life on earth.
I wouldn't worry too much though. Even the ancient Mayans predict the end of the world won't be 'till 2012. Many others predict it'll be tomorrow.
While it's not supposed dangerous for now, asteroid Toutatis is incredibly strange. And scientists are quite familiar with it, having bounced radar off the tumbling stone on previous flybys to generate computer renderings of its weird shape and movement.
Toutatis looks something like a dumbbell hurtling awkwardly through space. It has a crazy rotation that makes normal days impossible. Scientists can't explain the shape or the spin, but they're eager to learn more in September when, during the close pass, even backyard skywatchers will be able to spot the asteroid.
The orbit of Toutatis is pinned down with better precision than any other large asteroid known to cross Earth's orbit. Toutatis' 4-year trek around the sun ranges from just inside the Earth's path out to the main asteroid belt between Mars and Jupiter. The asteroid visits us every four years.
This fall, it will zoom by our planet within a million miles, or about four times the distance to the moon (1/4 million miles away).
That's close by cosmic standards for an object that could cause global devastation. Toutatis hasn't been so near since the year 1353 and won't be that close again until 2562, NASA scientists have calculated. No other asteroid so large is known to have come so close in the past, though accurate tracking of space rocks is a fairly recent, high-tech skill that still leaves wide margins of error for many objects.
Toutatis is about 2.9 miles long and 1.5 miles wide.
Many smaller space rocks have passed by much closer, well inside the Moon's orbit. Other asteroids in the size range of Toutatis have surely navigated that window, too, but were unseen in eras when the skies were not scanned so fully as today.
And throughout history, several asteroids and comets have hit the planet. In fact, an object the size of Mars hit Earth when it was very young, creating the Moon, scientists believe. But experts say the odds of a major collision in any year are extremely small. Any other near-Earth asteroid as big as Toutatis would almost surely be spotted decades or centuries before any possible impact (sure, that's why we, or I should say the French only discovered it in 1989).
The prediction of any such event would make huge news rather than small rumors.
Asteroid Toutatis, officially numbered 4179, was discovered by French astronomers in 1989. Researchers can't predict far enough into the future to rule out Toutatis ever slamming into Earth, so it is listed officially as a Potentially Hazardous Asteroid. NASA says it won't hit for at least the next six centuries.
Meanwhile, previous close approaches have allowed intriguing radar examinations of one of the oddest things in space.
"The vast majority of asteroids and all the planets spin about a single axis, like a football thrown in a perfect spiral," explains Scott Hudson of Washington State University. "But Toutatis tumbles like a flubbed pass."
The result is a lack of anything resembling a normal day or night on the giant, pockmarked space rock.
Instead of a fixed north pole, Toutatis' axis of rotation wanders around in two separate cycles of 5.4 and 7.3 Earth-days. Stars seen from any location on the asteroid "would crisscross the sky, never following the same path twice,'' Hudson says.
Steven Ostro at NASA's Jet Propulsion Laboratory has, with Hudson, studied Toutatis via radar on previous flybys. Ostro said that the population of near-Earth asteroids -- hundreds bigger than 0.6 miles (1 kilometer) have been found in the past six years or so -- are now known to come in "a zoo of shapes." And there are other asteroids that don't rotate on a single, main axis.
"But Toutatis remains the only non-principal-axis rotator in the solar system whose shape and spin state are well defined," Ostro said. More radar observations this year will try to further refine the spin rate and orbit.
There is more to learn. For starters, scientists also can't yet say if Toutatis has a hard surface or a thick layer of loose dirt similar to the moon.
"I'd very much like to know whether Toutatis' strange shape and ponderously slow, wobbly rotation are the result of collisional breaking apart or a gentle merger of the asteroid's two lobes, and when the responsible phenomena happened," Ostro said.
Answers to all these big questions might require an as-yet-unplanned visit.
"Because of the radar investigations, our physical characterization of Toutatis is the best we have for any Potentially Hazardous Asteroid," Ostro said. "But a spacecraft rendezvous could tell us a great deal more, and I would love to see this happen."
On Sept. 29, backyard skywatchers on Earth can find Toutatis, providing they know where to look.
Toutatis won't be visible to the unaided eye. Ordinary binoculars should be sufficient for spotting it if the sky is clear and dark, says Alan Harris, of the Space Science Institute in Boulder, Colorado.
"However, to actually know what your seeing, a small telescope would be useful," Harris says. That will allow you to detect the slow motion of Toutatis against background stars. The asteroid will appear as a point of light, much like a star. It is too far for surface details to be visible.
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