In 2029, the icy asteroid Apophis will fly past the Earth. Although scientists say a collision is out of the question, American engineers at MIT have developed a decision-making map just in case something goes wrong. The description is given in the journal Acta Astronautica.
April 13, 2029 asteroid 99942 Apophis, named after the ancient Egyptian god of chaos, will pass near the Earth. This block of ice the size of the Eiffel Tower, flying at a speed of 30 kilometers per second, will be so close that it is likely to affect the sphere of geostationary satellites located at a distance of about 36 thousand kilometers from Earth. This will be the closest approach to one of the largest asteroids in the next decade.
If the asteroid finds itself in the so-called gravitational well - the place where it will be captured by the Earth's gravitational field - it will change its trajectory and in 2036, the next time it flies past our planet, a collision may occur.
The results of all calculations show that the collision will not occur and the asteroid will safely fly by both in 2029 and in 2036. However, scientists at the Massachusetts Institute of Technology (MIT) have developed a so-called decision map, which looks at strategies for deflecting an asteroid from Earth.
In their calculations, the authors take into account the mass of the asteroid, its speed, proximity to a gravitational well and the time required to notify about the arrival of a celestial body. The asteroids Apophis and Bennu, another near-Earth asteroid, which are the target of NASA's OSIRIS-REx operational mission, which plans to deliver a sample of material from Bennu's surface to Earth in 2023, were taken as objects of modeling.
"People have mostly looked at last-minute deflection strategies, when the asteroid has already passed the keyhole and is heading towards the Earth," research director Sung Wook Paek said in an MIT press release. “We are interested in preventing passage through the keyhole. It looks like a preemptive strike with less uncertainty."
In 2007, NASA, in its report to the US Congress, concluded that if an asteroid is heading towards Earth, the most effective way to deflect it would be to launch a nuclear bomb into space. The force of its detonation will explode the asteroid, but our planet will be covered by a plume of nuclear explosion products. So the use of nuclear weapons to destroy asteroids is a highly controversial decision.
The second option is to send a "kinetic striker" to the asteroid - a spacecraft, rocket, or other projectile, which - if directed in the right direction and with sufficient speed - should, upon colliding with the asteroid, deviate from its course.
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“This physical principle is like playing billiards,” Peck explains.
However, for the success of a kinetic striker, one must know very accurately the trajectory of the asteroid's flight, its mass, momentum, and surface composition. Since none of these parameters are known for certain, scientists have to account for uncertainty. Peck and his colleagues developed simulation code to determine the likelihood of success in deflecting an asteroid, given a set of uncertainties in its properties.
As an option, the researchers propose to first send a reconnaissance ship to the asteroid, which will be able to clarify the parameters of this celestial body, or two ships, one of which measures the asteroid, and the second, sent a little later, may slightly deflect the asteroid even before the main drummer is sent.
The main final parameters of the modeling were: the proximity of the asteroid to the gravity well and the time remaining until the asteroid passed through it.
“The well is like a door - as soon as it opens, the asteroid will soon touch the Earth with a high probability,” says the scientist.
Scientists estimate that if Apophis passes through a gravity well in five or more years, there is time to send two reconnaissance ships. If the passage through the well occurs within two to five years, there is enough time to send only one reconnaissance ship - to measure the asteroid and adjust the parameters of the large striker. If less than one Earth year remains before the passage of the asteroid through the borehole, it will be too late to do anything.
“Even the main drummer may not be able to reach the asteroid within that time frame,” Peck concludes.
According to scientists, the collection of information and the manufacture of projectiles, strikers will take from two to five years.