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Hans
2009-Jan-10, 06:13 PM
A question was asked on another board which is well beyond my humble knowledge to answer.

It is:

"One [asteriod] in particular appears to be a near miss for earth but a bit too close to call for Venus in the very near future. Perhaps someone here has knowledge of this near miss and can direct me to the info"

If anyone has that information I'll link that person to this thread.

mugaliens
2009-Jan-10, 08:16 PM
Haven't heard. If it's true, it'd be a neat opportunity for a detailed doppler radar (3D!!!) view of the impact. Might even be worthwhile to send three of them up, in order to provide backup and to get it from at least two different angles.

stu
2009-Jan-10, 10:49 PM
If true, if the asteroid is small enough it's unlikely to make it through the Venusian atmosphere. The smallest craters on that planet are 3 km in diameter, and the surface pressure is equivalent to being under 1 km of water on Earth.

mugaliens
2009-Jan-11, 11:18 PM
If true, if the asteroid is small enough it's unlikely to make it through the Venusian atmosphere.

Well, that's it, then. I'm scrubbing the mission.

Hans
2009-Jan-12, 04:39 AM
Thank you gentlemen

I'll take this as "nobody has heard of it".

Ilya
2009-Jan-12, 02:08 PM
If true, if the asteroid is small enough it's unlikely to make it through the Venusian atmosphere. The smallest craters on that planet are 3 km in diameter, and the surface pressure is equivalent to being under 1 km of water on Earth.

It does not have to be THAT big. A 3 km crater corresponds to a 150-200 m impactor. Also, what counts for the purposes of stopping incoming projectiles is not pressure but density -- and air density at Venus' surface is still about 1/10 of water. There is no way a 150 m asteroid could punch through 1 km of water.

Arcane
2009-Jan-12, 05:37 PM
This one? http://www.spacedaily.com/news/asteroid-05d.html

1 in 300 chance of hitting Earth in 2029.

01101001
2009-Jan-12, 06:49 PM
This one? http://www.spacedaily.com/news/asteroid-05d.html

1 in 300 chance of hitting Earth in 2029.

I doubt it's the conjectured one that might hit Venus near future -- unless "near" means "not that near".

NEODyS: (99942) Apophis (http://newton.dm.unipi.it/cgi-bin/neodys/neoibo?objects:Apophis;main) gives no Venus approaches to 2100 (while listing 14 approaches of Earth in the same timeframe).

agingjb
2009-Jan-12, 10:22 PM
http://en.wikipedia.org/wiki/Venus-crosser_asteroid

has a couple of links to tables of approaches of asteroids to Venus (and other planets).

Swift
2009-Jan-12, 10:38 PM
http://en.wikipedia.org/wiki/Venus-crosser_asteroid

has a couple of links to tables of approaches of asteroids to Venus (and other planets).
Nice find. From there I found this table (http://members.shaw.ca/andrewlowe/ALL-PHAS.HTM#Venus). It lists the next close object to Venus as 1992 FE, on 7 April, 2015

stu
2009-Jan-15, 01:19 AM
It does not have to be THAT big. A 3 km crater corresponds to a 150-200 m impactor. Also, what counts for the purposes of stopping incoming projectiles is not pressure but density -- and air density at Venus' surface is still about 1/10 of water. There is no way a 150 m asteroid could punch through 1 km of water.

I wasn't trying to imply that the pressure was a factor, rather giving it as a conceptual idea of what the rock would be pushing through.

Also, I ran through the calculations and you'd need a ~400-m diameter impactor (assuming a density of 3 gm/cm^3 and velocity of 15 km/sec and a target of 5.243 with a surface gravity of 8.802 gm/sec^2). If your impactor velocity is 30 km/sec, then you can get away with a ~275-m projectile. So we're talking not small here, relatively speaking.

In addition, that calculation is assuming the projectile doesn't breakup at all nor does it lose material. Order-of-magnitude, it will lose as much material as it passes through ... but I don't know the column density of Venus' atmosphere off-hand. This all means it would need to be significantly larger as well as have a pretty good internal stability in order to survive break-up.