April is an important month for those concerned or perhaps obsessed with the asteroid Apophis, the “Serpent that dwells in darkness.” In 2002, following the discovery of the fate-laden space traveler, it was thought that an impact of the asteroid with Earth was probable; scientists were recalling the end days of the giant dinosaurs that once walked the Earth. In the years since then the potential for impact has been studied and is now considerably lower; basically the figure is about 2% to 3%; even lower probabilities have been seen in reliable media.
Friday, April 13, 2029, will be the next occasion of the asteroid’s by-pass of our earth. Scientists agree that the pass will be close, within the orbits of our satellites. Then, on Easter Sunday, April 13, 2036, the asteroid Apophis will pass our planet, even closer, with a diameter of 885 feet, a length of 460 feet, and moving at 13,129 mph. The basic premise is that impact is highly unlikely. Scientists allow that in the event of a collision in 2029 with a communication, or “geosynchronous” satellite, all previous computations become obsolete; both for 2029, and more so for 2036.
There are, we hasten to mention, factors contributing to general uncertainty. Basics, such as mass, and spin, have not been calculable. An indication of the asteroid’s direction of spin will be available in the year 2013. A retrograde rotation would result in a much higher impact probability. We consider, though, that because Apophis will pass through our orbiting satellites in a plane inclined at 40 degrees to the Earth’s equator, and passing outside the equatorial geosynchronous zone when crossing the equatorial plane, Apophis does not pose much threat to the satellites in the heavily populated equatorial region.
In a paper by JD Giorgini in 2008, which won an Edward Stone Award for an Outstanding Research Publication, Giorgini compares the impossibility of computation to the situation of having 6 apples. He makes the comparison thusly: The situation is similar to having 6 apples (the measured Apophis parameters) and 6 boxes whose contents are unknown (the unmeasured Apophis parameters). Boxes in hand, we then try to compute the probability that one has a total of 12 apples (impact probability). The result reflects back what is assumed about the unknown contents of the boxes, but fails to reveal new information. The contents of the boxes must be observed and measured to learn something new! Giorgini adds the variability brought about by solar energy, the heat of the sun, and concedes that the wide range of variables makes it impossible to predict if Apophis will have even a close encounter with Earth in 2036 when the orbital paths intersect.
In view of the complexities and uncertainties, all agree deflection is necessary. Explosion isn’t an option since that would produce many smaller objects hurling in all directions. NASA Scientists, as was discussed in my earlier article here at Blogcritics, have proposed a plan to alter the temperature of Apophis, on one side or the other, by spreading over the asteroidal surface a reflective or absorptive mesh which will affectively alter the asteroid’s temperature, therefore it’s course, and avoid a potential calamitous impact. Since the proposed mesh solution comes from the paper by JD Giorgini, and from NASA, we can only assume they are speaking in all seriousness.
With all the discussion today of the American economy, the public should have some awareness of this threat from the heavens, so that policy-makers will find it easier to devote money to this important research.