More on Asteroid Toutatis Passing Earth Sept 29th, 2004

A minor rumor has hatched on the Internet that a large and deadly asteroid will strike Earth this fall. Bulletin board discussions cite a 63 percent chance of impact, while concerned readers have e-mailed SPACE.com wondering if it is true.

The rumors are likely rooted in a real event, however. 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.

While not 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.

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.

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.

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 told SPACE.com 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.

"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, CO.

"However, to actually know what you're 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.

It's also interesting to ponder what Earth would look like form Toutatis. Ostro points out a simple relationship between the distance of Toutatis at this close approach and the size of the Moon. Toutatis will be four times farther than the Moon; the Moon is about ¼ the size of Earth.

"If you were on Toutatis and looked at Earth during the close approach, the Earth would look as large as the Full Moon does to us."

I am in the process of writing a book called "The Memoirs of a Rocket Scientist". :-)

Wow! Ping me when it's ready - I want a copy of the hardcover edition! I'm fascinated by the history of the space program, both ours and that of the old Soviet Union. There is plenty available about the astronauts, of course, but I want more on the science and engineering aspects. A lot more.

One of my favorite Apollo program books is Murray and Cox's "Apollo - The Race To The Moon". I'm afraid that too many tales of early NASA have already died with the old hands and not been recorded. That's unfortunate, because it's really fascinating stuff.

Another favorite: Stages To Saturn. I loaned out my hardcover copy years ago and never got it back. :-(

I'm sure you have already looked into all of this, but have you contacted Apogee Books? A book such as yours seems right up their alley.

Astronomers know nothing about the universe, except for a few large bodies with regular orbits. Any idiot should have understood that the latest by April 14, 2004, as comet Bradfield (diameter : 10,000 km) popped out of nowhere to become the largest body ever recorded in the inner solar system.

Transcript from http://edition.cnn.com/2004/TECH/space/09/28/asteriod.fly/index.html

HOW - 1. "actually you will not be able to see it ... "

Spotting Toutatis
Toutatis will not be visible to the unaided eye. Experienced telescope users can see it now from the Southern Hemisphere, and in early October it will be visible from the north.

Finding Toutatis will be challenging, Harris said, due to a combination of the asteroid's position in the sky and interfering moonlight.

Because the asteroid is so close, its location in the sky will vary significantly for skywatchers in different places on Earth at any given moment. And because it moves quickly, the location changes constantly. Printed sky maps don't always provide enough detail to be useful.

"In a large telescope the motion would be perceptible against any stars in the field more or less in real time, sort of like watching the second hand on a clock," Harris said, adding that the movement would be "not quite that fast, but noticeable."

Highly experienced observers will use complex plotting information known as ephemeris data. Others can use software programs that generate maps for specific times and locations.

At its closest on September 29, Toutatis will be visible only to observers in the Southern Hemisphere.

Large and steady binoculars will be able to pick out the pinprick of sunlight reflecting off the asteroid, providing observers "use a good program like Starry Night Pro to plot its incredibly rapid motion across the sky," said Clay Sherrod of the Arkansas Sky Observatory. (The software company Starry Night is owned by Imaginova, parent also of SPACE.com.)

Soon thereafter, experienced backyard astronomers north of the equator will have a chance to find Toutatis.

"By early October, it will suddenly be re-emerging into northern skies as its apparent trajectory will bring it back into very favorable view," Sherrod said in an e-mail interview. But by then the asteroid will be moving away from Earth and getting dimmer. It will quickly become "very difficult" to spot even with an 8-inch telescope, he said.

HOW - 2. "... but we already saw it "

Sherrod photographed the giant space rock last week (it was visible then in the north through large telescopes) and said exposures longer than eight seconds showed a trail as the giant rock moved slightly against the background of stars.

"It has been quite a wonderful show so far," he said.

HOW / WHY - "we know all about what's going on around us - even about the weirdest, smallest body"

Asteroid Toutatis was discovered in 1989. Scientists have modeled its strange rotation and odd shape -- it looks something like a pockmarked dumbbell -- on previous flybys.

Instead of a fixed north pole, Toutatis' axis of rotation wanders in two separate cycles of 5.4 and 7.3 Earth-days. So while most asteroids rotate somewhat like a football thrown in a perfect spiral, "Toutatis tumbles like a flubbed pass," says Scott Hudson of Washington State University.

Astronomers will use this week's flyby to examine Toutatis in greater detail, with a goal of pinning down the rock's rate of spin and better estimating its future path.

WHY - "relax, nothing is going to happen here, at least in your life time"

While some rumors have suggested the asteroid's forecasted course might be off by enough to cause a collision with Earth, Sherrod agrees with Harris and other scientists that there is no chance for calamity. Sherrod has been monitoring Toutatis' movement since July 3, logging more than 500 observations that allow mapping of a precise trajectory.

"Although the actual path of it has indeed varied a slight bit from the original calculated, there is absolutely no chance of a physical encounter or impact with Earth," he said.

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