The Planetary Society Blog
By Emily Lakdawalla
SECOND Biggest impact threat ever
Mar. 2, 2006 | 09:47 PST | 17:47 UTC
Note: One of my bosses, Bruce Betts, has just pointed out to me that Apophis (2004 MN4) actually reached a Torino scale number of 4 (with a 1 in 37 chance of impacting Earth) before further observations "beat it back" to its currently assigned value of 1, which makes 2004 VD17 the second biggest impact threat ever, not the biggest as I originally stated!
Yes, there's another hazardous asteroid out there, and it has been assigned the highest Torino scale number I've ever seen -- but it's still not particularly threatening. The body is called 2004 VD17, and it's roughly 500 meters in diameter. Its Torino scale number is listed at "2" (out of 10), which means: "Meriting attention by astronomers," or, more specifically, "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." Based on current state of information about the object, astronomers estimate a 1 in 1,560 chance that it'll hit Earth in the future. We have the full Torino scale on our website - go read it if you'd like to see how a "2" differs from a "1" (which is the current classification of Apophis (formerly known as 2004 MN4). VD17 has been a "2" for several months but it's coming into the news a bit more now which is why I decided to say something about it here.
Future observations of VD17 will most likely eliminate the impact possibility entirely, but there's a tiny possibility that refinement of the orbit will prove VD17's cone of possible paths to be one that intersects Earth's future path, in which case the impact probablility would increase. There's a really nice animation from the Spaceguard Foundation in Italy that shows how new observations refine our understanding of the position of an asteroid, and it's understanding the orbital position that's really important in figuring out future impact risk.
Here's several other useful resources for you to learn more about 2004 VD17:
2004 VD17 Orbit diagram from JPL (requires Java) - this is a really nifty interactive orbit applet; you can zoom in or zoom out or change the date and time and see if you can make VD17 hit Earth :)
2004 VD17 Earth Impact Risk Summary from the Near Earth Object Program at JPL - describes the characteristics of the potential impact...once you read that, you should definitely go to
Earth Impact Effects Program at the University of Arizona and see what it would be like to be close to or far away from such an impact
Ephemerides etc. for 2004 VD17 from NeoDys
So, anyway, it's probably not going to hit us. What it's going to do instead is to pass very close by us at some point, which will make it an easy target for astronomers -- something to celebrate, not fear. However, its close approaches will be happening in 2102 and 2104 -- not for a very long time. For that reason, Apophis (2004 MN4) is the one to watch, because its first close approach is coming up much sooner, in 30 years (2036) -- which is I think a comfortable amount of lead time to actually develop some nifty program combining a long baseline of Earth observations with some little mission. For example, you could impact Apophis with a transponder, and track it really accurately.
Comments
This comment form is powered by GentleSource Comment Script. It can be included in PHP or HTML files and allows visitors to leave comments on the website.
| 
