Wow for some reason 18,300 miles doesn’t seem quite as far anymore.
(Video Credit – Wired Science)

Meet Apophis. Discovered in 2004, it will likely set a record for harmless near earth pass in 2029.

Earlier data pointed to the asteroid potentially passing through a troublesome gravitational keyhole which increased the threat to Earth in 2036, however new data from previously unreleased images from a University of Hawaii telescope near the summit of Mauna Kea have allowed NASA scientists to improve their models. New models show a reduced risk of collision in 2036 from 1 in 45,000 to 1 in 250,000.

From the NASA press release:

“The refined orbital determination further reinforces that Apophis is an asteroid we can look to as an opportunity for exciting science and not something that should be feared,” said Don Yeomans, manager of the Near-Earth Object Program Office at JPL.

Modeling asteroids and allowing humanity a chance to risk assess is only one example of the power of computer modeling. However, this example also illustrates one important caveat about modeling. One’s model is only as good as the data utilized in generating and analyzing it. Let’s hope that future data on Apophis continues to produce good news.

(Image Credit)

In December 2004, astronomers discovered an asteroid designated 2004 MN4. Now, I’m fairly certain that, under normal circumstances, this would have just been recorded and noted, and the world would have happily moved on, never thinking twice about 2004 MN4.

Of course, the fact that I’m talking about it now, almost 5 years later, suggests that there was nothing normal about these circumstances. The basic story is that computer modeling of the trajectory of 2004 MN4, later called 99942 Apophis (after the Egyptian serpent god known as “The Uncreator”) revealed that this near-earth asteroid had a score of 2 on the Torino scale, a number which calculates how much we should worry about a particular asteroid/comet, the highest score of any near-earth object ever (as far as I know). And what does a 2 mean? According to the Torino scale, a 2 is “merely”:

A discovery, which may become routine with expanded searches, of an object making a somewhat close but not highly unusual pass near the Earth. While meriting attention by astronomers, there is no cause for public attention or public concern as an actual collision is very unlikely. New telescopic observations very likely will lead to re-assignment to Level 0 [no risk]

What the computer modeling showed was that there was a range of trajectories that the asteroid could take (the range stemming from a number of uncertainties), and a few of them could hit Earth (at a probability of about 3%) in 2029.

The result of the impact? As Apophis is roughly the size of the Rose Bowl, it has been estimated that upon impacting the Pacific Ocean (where its currently estimated to be if it does hit), Apophis would cause a hole in the ocean roughly 3 miles deep and 3 miles wide, which would then follow with a series of tidal waves so destructive that it would eradicate any cities and regions unfortunate enough to be on the Pacific.

Thankfully, subsequent modeling involving more data and more calculations showed that the probability of hitting the Earth dwindled to near 0% (1 in ~45000 to be more precise) in 2029, although interestingly enough, when the asteroid passes by the Earth in 2029, it has been predicted to pass close enough that it actually dips below the altitude at which many satellites orbit (causing a bizarre NASA-German student debate over the probability of impact increasing because of a collision with a satellite).

However, we are not out of the woods yet. Just because 2029 is relatively safe, doesn’t mean that 2036 is. It turns out that Apophis has a troublesome gravitational keyhole. If a near-earth asteroid happens to pass through this gravitational keyhole, a very narrow region of space which in the case of Apophis is an area roughly 2000 feet in diameter, then the Earth’s gravitational field will actually deflect the asteroid’s orbit almost guaranteeing that Apophis will hit the earth in April, 2036.

So, the two big questions for humanity (and a third about science):

1. Will Apophis pass through its gravitational keyhole when it swings by the Earth in 2029?
2. If yes, what hope does humanity have of deflecting said asteroid?

The answer to both will require extensive computer modeling. The challenge of the first question is particularly intensive as the gravitational keyhole (which we have a good sense of) is so small, and yet the number of potential influences on Apophis’s trajectory is so large. Not only does one need to deal with the gravitational pull of the Earth, Moon, and Sun, one has to factor in things like the spin of the asteroid, the asteroid’s ability to absorb and reflect sunlight, and even the gravitational pull of other near-earth asteroids!

The challenge of the second question is not only technological (do we use nuclear weapons? rockets? lasers? can we coat the asteroid with a reflective material to change its absorption of sunlight?), but also one of modeling. This one is especially challenging, as even assuming that mankind is able to deflect the asteroid (and not just shatter it, leaving many many little asteroids to hit the Earth), various space agencies will likely have to continue tracking Apophis to make sure that the deflection did not cause the asteroid to change course to potentially hit the Earth again.

Do we have the computer technology and the mathematical wisdom to solve these questions? I sure hope so. 2029’s not all that far off…

(Image credit)