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Apophis collision more likely February 16, 2006

Posted by dr. gonzo in Asteroids, Space.

The National Aeronautics and Space Administration maintains a Web site which disseminates information on Near Earth Objects. Link to it here.

What is a NEO, you ask?

“Near-Earth Objects (NEOs) are comets and asteroids that have been nudged by the gravitational attraction of nearby planets into orbits that allow them to enter the Earth’s neighborhood. Composed mostly of water ice with embedded dust particles, comets originally formed in the cold outer planetary system while most of the rocky asteroids formed in the warmer inner solar system between the orbits of Mars and Jupiter. ”

How many are there?

As of February 09, 2006, 3,933 Near-Earth objects have been discovered. 830 of these NEOs are asteroids with a diameter of approximately 1 kilometer or larger. Also, 748 of these NEOs have been classified as Potentially Hazardous Asteroids (PHAs).”

NEOs spent some time in the news, when the story about Apophis broke, last year. Asteroid 2004 MN4 (Apophis), when first discovered, was seemingly on a collision course with Earth, one much more certain than its current course. This Guardian article is great background on Apophis’ story.

I haven’t seen anything in the mainstream press about Apophis lately but between Feb. 5 and Feb. 16 Apophis’ chances of hitting Earth got a little bit better.

If you look at the NEO Web site, on Feb. 5 and Feb. 16, the impact probability has changed, not only for Apophis but for asteroid 2004 VD17 as well (on the links the two asteroids of concern are at the top, highlighted in green on the 15th and Apophis is at the top and VD17 is just below the first list on the Feb. 4 link, again they are in green). The other asteroid that has cracked level one (green) on the Torino Scale, 1997 XR2, still sits at a 1 in 10,000 chance of hitting Earth. Together, these three asteroids represent those known that are most likely to collide with our home planet.

I have included the screen grabs from each day below, as well, in case the cached link doesn’t work for some reason.

Click to enlarge.

Basically what those statistics mean is that the asteroid Apophis went from a 1 in 6,250 chance of hitting Earth to a 1 in 5,880 chance of hitting Earth. That’s not all. The year range for the potential impacts and the number of potential impacts went up as well. On Feb. 5 there were only 2 potential impacts, today there are 4. The year range changed from 2036-2037 to encompass the years 2036-2062.

The other asteroid, 2004 VD17, went from a 1 in 3,230 chance of hitting Earth to a 1 in 2,780 chance of hitting Earth. In addition its number of potential impacts went from 2 to 3. The range of years for collision with 2004 VD17 also changed. On Feb. 5 this NEO had a chance of hitting earth between 2102-2104, the year range has been updated and is now 2096-2104. Besides just the numbers changing for 2004 VD17 it moved from the list of objects “not recently observed” to the list of objects “recently observed (within the past 60 days).” This, of course, means between the fifth and the 16th that 2004 VD17 was observed.

I should note that the probability that these asteroids will miss Earth entirely is much greater than the probability that they will strike the planet. NASA updates this list constantly, so I’ll watch it occasionally for any developments.

Screen Grab 1: NEO Web site on Feb. 5, 2006, note the impact probability, number of potential impacts and year range for Apophis. Screen Grab 2: NEO Web site on Feb. 16, 2006, note the above as well as the addition of 2004 VD17, for that asteroid note the same items. Screen Grab 3: NEO Web site on Feb. 5, 2006, note the above and notice that it is listed as “not recently observed.”

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