So….why do we look for them if we don’t have anything in place to remove the threat again? I must’ve missed that memo…..

So, without data on how many of these things are out there and how close by us they pass, how would we ever get funding for projects to work out how to deal with one that’s going to hit?

@Ray, ANYTHING coming in toward Earth is either an asteroid (even dust grains can be considered as such) or comet. THAT is dependent on orbital characteristics.
25 meters sounds like a good sized rock, until it comes toward you around mach 25!

As for risk to Earth from something this size, we’ve monitored 15-20 meter meteors exploding fairly often with our nuclear weapons monitoring systems. They typically detonate many miles above the surface of the Earth. At worst case, it’d likely explode at low altitude (3-6 miles AGL), causing very similar effects to the Tunguska event. Most likely and common, it’ll begin to break up, larger parts stay together until around 20 miles AGL, then it explodes harmlessly.
Now, if we have an accurate path for entry, we can gather small chunks (ala “Meteor men”) for study, learning more about density and detonation of meteors.
As this is going to be a clean miss, it’s a moot point.

Hey, Phil. You’ve been monitoring its trajectory. How much is the Earth perturbing that pebble’s orbit? That close should have a rather moderate effect on its orbit, though I doubt it’ll be “evicted”.

Absolutely a collision between a satellite and an asteroid would be possible. For all we know, it’s already happened: there are a lot more small rocks Out There than large ones. A rock the size of your fist would still destroy a satellite, but would be essentially undetectable Down Here. So I’d suggest it’s possible (although spectacularly unlikely) that any satellite which suddenly exploded could have been the victim of such a hit as you asked about.

Having said that, the thing to keep in mind that geosynchronous satellites orbit directly above the Earth’s equator. That narrows down the target area a lot. Rocks orbiting the Sun could conceivably come at us from any direction, so just because a rock comes closer to the Earth than geosynchronous satellites doesn’t mean it crossed the actual orbit that those satellites occupy (in the same way that two planes can occupy the exact same latitude and longitude, but won’t collide because they’re at different altitudes).

Mostly for scientific reasons. “Planetary defence” is just a nice bonus.

However, even knowing a few days or even hours in advance of an actual impact could be valuable. For a small object like this it would be of scientific interest to observe the impact and to go look for fragments.

For something a bit larger warning people could make a big difference to casualties: evacuation of a direct impact zone might be possible and there’d a large area around the impact where simply taking cover, boarding up windows and that sort of thing would help a lot. An ocean impact causing a tsunami would be easy to mitigate by evacuations of low areas around the basin in question, shutting down nuclear reactors, and so on.

Also, a relatively small impact in an area of the globe where tensions are already high could lead indirectly to catastrophic consequences which could be averted by prior information. E..g., suppose there had been unexpected new crater in Israel or Iran a while ago – would there not have been a severe risk of “retaliation”?

The cost of the surveys is, in the grand scheme of things, tiny and the combination of scientific information and the potential for warning makes them well worthwhile.

Development of technology to deflect or destroy the asteroid would be more double edged because of the risk of abuse. Also, it’d be a lot more expensive.