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A Meteorite Found in Lord Pakal's
Tomb Tells Us of Ancient Warning



2012 Comet in the Sky

An improved estimate of the number of nearby asteroids still capable of causing local destruction suggests these pesky rocks are likely to hit Earth about once every 1,000 years. Astronomers had thought such minor catastrophes occurred about once per century.

The new calculations, from Alan Harris of the Space Science Institute in Boulder, CO, show there are about 500,000 relatively small asteroids that inhabit roughly the same region of space through which Earth orbits. The asteroids are in the 50-75 meter (165-245 foot) size range.

Rocks this size can flatten a forest and would cause tremendous damage and even death if it targeted a city.

About 1,100 large Near Earth Objects (NEOs) are thought to exist. More than 600 have been found by programs stemming from a NASA effort to locate 90 percent of them by 2008. None are known to be on a collision course with Earth.

Smaller asteroids are harder to detect, however. Now and then, one passes relatively close to the planet and some are spotted only after such flybys. A few vocal scientists have long called for stepped-up funding to find these smaller NEOs, because they are more likely to strike and are a more immediate threat.

NASA's line has been to find the big ones first, then consider going after the smaller ones. Only recently, however, have discussions on how to do this become serious. New telescopes would be needed, and telescopes generally take a few years to design and build.

Suppose a giant asteroid or comet is heading toward Earth right now. Impact is certain. The consequences are expected to be globally devastating, with the human race among the casualties. The chances of doing anything about it are zero, the government decides.

Would you want to know?

(Article modified from - Feb. 2003)

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According to the scientific article, "Motion of the Minor Planet 4179 Toutatis: Can We Predict Its Collision with the Earth?, written by Sitarski, G. (1998), Minor planet 4179 Toutatis is an Apollo type object with a very small orbit inclination (i=0.47 arcdeg), hence it has a possibility to approach closely the Earth (an encounter to within 0.01 a.u. is expected in 2004) and might be a good candidate for a future collision with the Earth.

The author collected 640 astrometric observations of Toutatis from the period 1934-1997 to improve the orbit. The data had to include a nongravitational term into equations of motion expressed by a secular change dot{a} of the semi-major axis a of the Toutatis orbit to obtain a fully satisfactory solution of the orbit determination. A value dot{a}=-0.16*10^{-10} is two orders smaller than that determined in the case of short-period comets with known nongravitational effects. To investigate the long-term motion of Toutatis the researcher numerically integrated the equations of motion by recurrent power series taking into account perturbations caused by the eight planets from Mercury to Neptun, treating the Earth and Moon as separate bodies, and also by the four biggest asteroids.

Data was randomly varied the orbital elements to examine the Toutatis' motion for a number of different orbits. The author presents a new method of the random orbit selection which allows the simulation to find a set of different orbits but representing well all the observations used for the orbit correction. Their results confirm a conclusion found by other authors that Toutatis orbit is exceptionally chaotic. Therefore, he was not able to predict the motion of Toutatis further than for 300 years.

However, their integrations spanning 1500 years showed that the evolution of position of the descending node of Toutatis' orbit might go also in such a direction that the orbits of Toutatis and of the Earth would intersect in the future. Hence a possibility of the Toutatis-Earth collision is not excluded but it is completely unpredictable.

To investigate conditions of a hypothetical collision of a minor planet with the Earth the author made the following numerical simulation. Based on the Toutatis' orbit he deduced such orbital elements for a fictitious minor planet "Fatum" that a shape of the orbit was very similar to that of Toutatis, but he knew in advance that "Fatum" would certainly collide with the Earth in September 2004 and he calculated values of the impact parameters. The author created a set of 638 artificial observations of "Fatum" in 1988-1997 for the same dates and with the same random observational errors like those of Toutatis. Then he corrected the "Fatum's" orbit for different observational intervals to examine the exactness of the impact prediction in 2004.

The numerical simulation found that in 1993 we would be sure that the collision is inevitable, and in 1997 we could determine an impact area on the Earth's surface in range of a square of 100*100 km. The author shows that if we knew the impact date so early we could undertake an action to avoid the collision by trying to change the "Fatum's" heliocentric velocity only by one cm/sec.

Title: Motion of the Minor Planet 4179 Toutatis: Can We Predict Its Collision with the Earth? Authors: Sitarski, G. Journal: Acta Astronomica, v.48, pp.547-561, (1998). Publication Date: 09/1998.

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