Asteroid Toutatis Passes Near Earth

Date November 29, 1996

Discovered and named in 1989, the asteroid Toutatis, which passes near Earth roughly every four years, not only promises astronomers unprecedented access to data concerning asteroid formation but also has generated frank discussions concerning possible scenarios should an object of that magnitude ever collide with Earth.

Locale Orbit between Earth and the main asteroid belt between Mars and Jupiter

Key Figures

• Christian Pollas (fl. late twentieth century), French astronomer

Summary of Event

On January 4, 1989, asteroid 4179 was discovered by French astronomer Christian Pollas while he was working at the Observatoire de la Côte d’Azur at Caussols, in southern France. Pollas, a veteran astronomer credited with discovering numerous asteroids, happened to spot the bright, fast-moving object on photographic plates that had been taken in an effort to measure the telemetry of Jupiter’s obscure satellites. Pollas named the asteroid Toutatis after a powerful, protective god of fertility, war, and prosperity common to both Gallic and Celtic mythologies. As Pollas found out, however, Toutatis was also a deity figure in Les Aventures d’Asterix, a hugely successful, long-running French comic book series set in medieval Europe; ironically, in the series, the tribe that worships Toutatis is convinced the sky is soon to fall. Once the new asteroid was identified, its approach was tracked by the scientific community, which confirmed its Earth-crossing orbit, its speed (roughly 67,112 miles per hour), and its dimensions (2.9 miles long, 1.5 miles wide, 1.2 miles thick, considerable for asteroids).

Apart from the usual scientific buzz that inevitably accompanies the identification of any new heavenly body, particularly a near-Earth object, the discovery of Toutatis brought additional excitement because, given the asteroid’s location—just inside the Earth’s orbit out to the main asteroid belt between Mars and Jupiter—it would return to the Earth’s observation roughly every four years. Further, its particularly low orbit would bring the asteroid close to the Earth—relative to space measurement. In 1992, for instance, the asteroid came within 2.5 million miles; in November, 1996, 3.3 million miles; and in September, 2004, just over 1 million miles, the closest approach of any known object until 2060. Such regular “close” brushes have enabled astronomers unprecedented access to the asteroid using only Doppler ground radar without having to launch satellites to obtain the data. Following the 1996 pass, for instance, the NASA Jet Propulsion Laboratory in Pasadena, California, released startlingly vivid delay-Doppler radar images of the asteroid’s pocked surface. Indeed, in its 2004 flyby, Toutatis was visible for backyard sky watchers with only binoculars.

Thus, within the relatively brief time Toutatis has been known, scientists have been able to study it. They have found that it is quite an unusual object, which led, in turn, to alarmist concerns. The images of Toutatis revealed that it did not possess an asteroid’s usual spherical shape; rather, it is oblong with a peanut-shell shape, with one lobe substantially smaller than the other. Astronomers conjecture that, given the asteroid’s heavily cratered face, Toutatis was once two asteroids that slammed together in a violent fusion.

Further intriguing astronomers was Toutatis’s irregular rotation: Asteroids spin in a tight and predictable spiral, like a child’s top, along a single axis of rotation; but Toutatis spins in a wobbly, tumbling motion—the result, astronomers theorize, of numerous collisions with other floating debris. Consequently, Toutatis does not have a fixed pole of rotation; rather, it follows what is termed non-principal axis rotation—quite a rare occurrence. Toutatis maintains two entirely different rotation motions, which means that if a person could actually stand on the asteroid, he or she would see the Sun rise and set along a different path each day. Thus the asteroid does not maintain a fixed “day”; rather, it completes its spin sometimes in 5.4 days and sometimes in 7.3 days, a period that in either case is far slower than those of most asteroids.

The implications for scientific investigation were promising: Given the asteroid’s irregular rotation, its quadrennial flybys, and its slow tumbling movement, Toutatis would expose virtually its entire circumference at one time or another for Earth observation. The scientific community came to view the regular approach of Toutatis as an opportunity to advance theoretical explanations for the beginnings of the universe, as asteroids are widely believed to be debris left over from initial cosmic eruptions that first forged the planets and the stars. Asteroids’ mineral contents are particularly helpful in directing such theories. Given Toutatis’s relatively close orbit, the scientific community has raised the possibility of launching a robotic exploratory vehicle to engage the asteroid and to determine its exact mineral makeup during one of three approaches in the 2020’s.

The very characteristics of Toutatis’s orbit that have so intrigued scientists, however, have caused alarm in the lay community. Such alarm was perhaps inevitable when, because of its orbit, Toutatis was pro forma designated early on as a “potentially hazardous asteroid” (PHA). Asteroids have been known to collide with the Earth’s surface. Most recently, a devastating strike took place in 1908 in Tunguska, Russia, in which an asteroid much smaller than Toutatis leveled more than 700 square miles of Siberian wilderness. An asteroid roughly twice the size of Toutatis is believed to have caused the extinction of the dinosaurs more than sixty million years ago. Astronomers have conjectured that asteroids regularly collided with the Earth during its earliest eons of formation and that the cratered face of the Moon verifies the impacts of such collisions. Given the traffic of asteroids currently in the solar system (conservative estimates suggest more than 300,000 such objects of at least 300 feet long), scientists have long held that collisions with the Earth are inevitable, although they predict such collisions would occur only every thousand years or so.

The topsy-turvy orbital patterning of Toutatis, however, means that scientists cannot confidently predict the exact path of Toutatis’s approaches beyond several centuries. In fact, given the asteroid’s unusually low inclination—less than half a degree from Earth’s—in several computer scenarios played out six centuries into the future, Toutatis is tracked to actually collide with the Earth, encouraging lay speculation to dub the mountainous asteroid the “Doomsday Rock.” Such speculation routinely describes Toutatis’s eccentric orbit as “unpredictable,” although scientists quickly point out the significant difference between an “unpredictable” orbit and Toutatis’s “irregular” orbit, which is unique but definitely patterned.

Nevertheless, within the nonscientific community (fed by Internet hype), each approach of Toutatis triggers a considerable volume of alarmist misinformation suggesting that the asteroid’s close pass confirms anxieties about an apocalyptic collision with the Earth, although astronomers are quick to point out that “close” still assures millions of miles between the Earth and the asteroid. The asteroid’s 1996 flyby, however, inspired two disaster movies: the 1998 blockbuster Armageddon, in which a emergency space mission must detonate an approaching asteroid, and, that same year, the less successful Deep Impact, in which a chunk of a rogue comet actually strikes the Earth and triggers monumental destruction on the East Coast of the United States.

Significance

Although Toutatis offers a rare opportunity for astronomical observation, it has also occasioned a concerted effort by an international cartel of scientists, astronauts, diplomats, insurance executives, lawyers, and astrophysicists to petition the United Nations to draft a specific protocol for addressing the threat of a collision. Despite the mathematical certainty that an asteroid of considerable dimension will collide with the Earth, no framework exists setting out a concrete course of response.

In 2007, a U.N. blue-ribbon committee submitted a draft of just such a global policy, including recommendations for determining which governments would be charged with directing attempts to deflect any incoming objects and a proposed structure for international relief operations should a catastrophic collision occur. Debate on the protocol is set to conclude by 2009. Given the enormous reach into the visible universe afforded by computer-enhanced observation technologies and the detection over the last decade of many new PHAs—as many as 20,000 of which have yet to be exactly identified—the National Aeronautics and Space Administration was charged by Congress in 2005 to increase its efforts agressively both to identify asteroids that could pose a threat to the Earth (only one hundred such objects had been cataloged by 2007) and to investigate feasible strategies of preparation should the planet face such a threat.

Bibliography

Bobrowsky, Peter T., and Hans Rickman, eds. Comet/Asteroid Impacts and Human Society: An Interdisciplinary Approach. New York: Springer, 2007. Measured analyses that project the immense cultural and social alterations in the event of an impact.

Hallam, Tony. Catastrophes and Lesser Catastrophes: The Causes of Mass Extinction. New York: Oxford University Press, 2005. From a distinguished geologist, a look at historic evidence of catastrophes including asteroid impacts. Closes with a review of current international efforts—scientific, technological, and political—to confront such collisions.

Palmer, Trevor. Perilous Earth: Catastrophe and Catastrophism Through the Ages. New York: Cambridge University Press, 2003. Written for a general audience but grounded in meticulous research, the book explores the differences between preparation and panic.

Spangenburg, Ray, and Kit Moser. If an Asteroid Hit the Earth. New York: Franklin Watts, 2000. Sobering analysis of the effects of an asteroid hit. Includes helpful context concerning past collisions.

Verschuur, Gerrit L. Impact! The Threat of Comets and Asteroids. New York: Oxford University Press, 1997. Landmark investigation into historic collisions and their impact, particularly the Tunguska catastrophe.