<p>As of 2023, there were <a href="https://space.stackexchange.com/q/88/2847">about 16,000,000 kg of objects in Earth orbit</a>.  <a href="https://en.wikipedia.org/wiki/99942_Apophis" rel="nofollow noreferrer">99942 Apophis</a> is estimated to weigh roughly 61,000,000,000 kg.  Even if it were to somehow hit <em>all</em> of them, it out-weighs them by about 4000:1, and those satellites aren't moving 4000 times faster than the asteroid.  It would simply sweep them up and carry them with it on its way out of the system.</p>
<p>It's unlikely that Apophis will hit anything: the point of closest approach is well above the semi-synchronous orbit used by GPS satellites, and <a href="https://cneos.jpl.nasa.gov/doc/apophis/" rel="nofollow noreferrer">the trajectory stays away from the equatorial belt used by geostationary satellites</a>.</p>

CC BY-SA 4.0
2024-03-29T03:01:35.870Z
What if a lot of them hit the asteroid in the opposite direction?That would still mean stuff from the asteroid can fall onto Earth in large quantities and if the material is all in the form of big rocks that are many millions of tons then the chunks falling is still a problem right? Is it possible that Apophis could send lots of space junk to Earth?
MiltonTheMeme
CC BY-SA 4.0
2024-03-29T06:59:17.717Z
"...and the trajectory stays away from the equatorial belt used by geostationary satellites..." can this be supported with a source, at least for the [2029 approach](https://en.wikipedia.org/wiki/99942_Apophis#2029_close_approach)? *Thanks!*
uhoh
CC BY-SA 4.0
2024-03-29T20:21:49.203Z
@uhoh, https://cneos.jpl.nasa.gov/doc/apophis/, section "Future", and in particular, the line "and passing outside the equatorial geosynchronous zone when crossing the equatorial plane, it does not threaten the satellites in that heavily populated region".
Mark
CC BY-SA 4.0
2024-03-29T20:30:10.003Z
@MiltonTheMeme, basic conservation of momentum says that even if the satellites hit going exactly the opposite direction, they're not going fast enough to slow it down for a drop.  At a rough estimate, Apophis at closest approach will be going twice as fast as a satellite in an impacting orbit.  That means a satellite can, at best, bring down a chunk weighing half as much as it does: a two-ton satellite can bring down no more than a ton of rock.  Rocks that size burn up in the atmosphere several times a year.
Mark
CC BY-SA 4.0
2024-03-29T21:47:45.493Z
More mass than the satellite can still escape from the asteroid from the collision given that all the fragments go slower right?
MiltonTheMeme
CC BY-SA 4.0
2024-03-29T22:06:39.100Z
@MiltonTheMeme, "slower" isn't enough.  In order to hit the Earth, you need the fragments to slow down to a near-stop; anything less, and they'll either end up in Earth orbit or continue back into interplanetary space with the rest of the asteroid.
Mark
CC BY-SA 4.0
2024-03-30T02:23:17.947Z
@Mark [+1] and  *Thanks!* Ideally that could be moved to the answer post itself where future readers will be sure to see it. May readers (and "scrapers") ignore comments, and in Stack Exchange comments are by definition considered temporary and might disappear at any time (though that doesn't normally happen in practice).
uhoh
CC BY-SA 4.0
2024-03-29T02:25:43.547Z
2024-03-30T05:20:52.387Z
2024-03-30T05:20:52.387Z
Mark
<p>Would the Apophis asteroid fall to Earth in 2029 due to space junk from broken rockets falling into the asteroid and impacting it, effectively exerting a sort of frictional force in a sense to the asteroid kind of like air resistance does?</p>
<p>Would satellites be affected by its gravity in a significant enough manner? Because it is possible that its trajectory can change by something hitting it at ~34000 mph from a space junk 1000 kg satellite hitting it from the opposite side and from asteroid's perspective it is as if it has double the velocity.</p>
<p>Considering the Dart mission was able to change trajectory, is it possible that Apophis changes trajectory and enters closer to Earth and falls in or breaks apart through the Roche limit?</p>

CC BY-SA 4.0
2024-03-12T20:21:33.703Z
This is an interesting question! [Apophis is only thought to be about 6E+10 kg](https://en.wikipedia.org/wiki/99942_Apophis) and only a small perturbation is necessary to make a significant change in the probability of hitting Earth in the future. The chances of that being space junk are pretty small, there's very very little space junk beyond of GEO but the 2029 closest approach is predicted to be only 38,017.0±3.4 km, *within GEO!* Hmm...
uhoh
CC BY-SA 4.0
2024-03-12T20:51:19.697Z
Only 6E+10 kg? What's the mass of the typical space junk in comparison? Probably small and will not change the momentum of Apophis on this visible, but as @uhoh mentions, future visits could be different.
JohnHoltz
CC BY-SA 4.0
2024-03-13T02:15:56.690Z
Take the heaviest satellite. Compute the maximum momentum transfer from a head-on collision. See what happens.
Jon Custer
CC BY-SA 4.0
2024-03-13T03:39:52.720Z
Even the ISS is only ~420 tonnes. That's not going to have much impact on a 60 million tonne asteroid.
PM 2Ring
CC BY-SA 4.0
2024-03-13T03:49:37.520Z
@PM2Ring yep, it just depends on how keyholeish and chaotic this specific n-body scenario is over the next several centuries. [Do all dangerous asteroids first pass through keyholes?](https://space.stackexchange.com/q/41550/12102)
uhoh
CC BY-SA 4.0
2024-03-13T21:06:27.733Z
Spacejunk hitting the asteroid could also cause the asteroid to break up into pieces, which is still probably not good for anyone on Earth, so that could still be a problem. Even a 1000 kg broken off rock from the asteroid is still really problematic and considering that the asteroid broken off part probably will still have its tangential velocity, so its total kinetic energy at impact will still be substantial.
MiltonTheMeme
<artificial-satellite>
If Apophis hits spacejunk in 2029 near the Earth is it possible that it could in theory make the asteroid fall into Earth?
MiltonTheMeme
# If Apophis hits spacejunk in 2029 near the Earth is it possible that it could in theory make the asteroid fall into Earth?

(Asked by: username_0 on 2024-03-12)

Would the Apophis asteroid fall to Earth in 2029 due to space junk from broken rockets falling into the asteroid and impacting it, effectively exerting a sort of frictional force in a sense to the asteroid kind of like air resistance does?

Would satellites be affected by its gravity in a significant enough manner? Because it is possible that its trajectory can change by something hitting it at ~34000 mph from a space junk 1000 kg satellite hitting it from the opposite side and from asteroid's perspective it is as if it has double the velocity.

Considering the Dart mission was able to change trajectory, is it possible that Apophis changes trajectory and enters closer to Earth and falls in or breaks apart through the Roche limit?

**Tags:** artificial-satellite
> **Comments:**
> **username_1**: This is an interesting question! [Apophis is only thought to be about 6E+10 kg](https://en.wikipedia.org/wiki/99942_Apophis) and only a small perturbation is necessary to make a significant change in the probability of hitting Earth in the future. The chances of that being space junk are pretty small, there's very very little space junk beyond of GEO but the 2029 closest approach is predicted to be only 38,017.0±3.4 km, *within GEO!* Hmm...  
> **username_2**: Only 6E+10 kg? What's the mass of the typical space junk in comparison? Probably small and will not change the momentum of Apophis on this visible, but as @uhoh mentions, future visits could be different.  
> **username_3**: Take the heaviest satellite. Compute the maximum momentum transfer from a head-on collision. See what happens.  
> **username_4**: Even the ISS is only ~420 tonnes. That's not going to have much impact on a 60 million tonne asteroid.  
> **username_1**: @PM2Ring yep, it just depends on how keyholeish and chaotic this specific n-body scenario is over the next several centuries. [Do all dangerous asteroids first pass through keyholes?](https://space.stackexchange.com/q/41550/12102)  
> **username_0**: Spacejunk hitting the asteroid could also cause the asteroid to break up into pieces, which is still probably not good for anyone on Earth, so that could still be a problem. Even a 1000 kg broken off rock from the asteroid is still really problematic and considering that the asteroid broken off part probably will still have its tangential velocity, so its total kinetic energy at impact will still be substantial.  

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## 1 answers

### Answer by username_5 on 2024-03-29. Score: 2

As of 2023, there were [about 16,000,000 kg of objects in Earth orbit](https://space.stackexchange.com/q/88/2847). [99942 Apophis](https://en.wikipedia.org/wiki/99942_Apophis) is estimated to weigh roughly 61,000,000,000 kg. Even if it were to somehow hit *all* of them, it out-weighs them by about 4000:1, and those satellites aren't moving 4000 times faster than the asteroid. It would simply sweep them up and carry them with it on its way out of the system.

It's unlikely that Apophis will hit anything: the point of closest approach is well above the semi-synchronous orbit used by GPS satellites, and [the trajectory stays away from the equatorial belt used by geostationary satellites](https://cneos.jpl.nasa.gov/doc/apophis/).

> **Comments:**
> **username_0**: What if a lot of them hit the asteroid in the opposite direction?That would still mean stuff from the asteroid can fall onto Earth in large quantities and if the material is all in the form of big rocks that are many millions of tons then the chunks falling is still a problem right? Is it possible that Apophis could send lots of space junk to Earth?  
> **username_1**: "...and the trajectory stays away from the equatorial belt used by geostationary satellites..." can this be supported with a source, at least for the [2029 approach](https://en.wikipedia.org/wiki/99942_Apophis#2029_close_approach)? *Thanks!*  
> **username_5**: @uhoh, https://cneos.jpl.nasa.gov/doc/apophis/, section "Future", and in particular, the line "and passing outside the equatorial geosynchronous zone when crossing the equatorial plane, it does not threaten the satellites in that heavily populated region".  
> **username_5**: @MiltonTheMeme, basic conservation of momentum says that even if the satellites hit going exactly the opposite direction, they're not going fast enough to slow it down for a drop.  At a rough estimate, Apophis at closest approach will be going twice as fast as a satellite in an impacting orbit.  That means a satellite can, at best, bring down a chunk weighing half as much as it does: a two-ton satellite can bring down no more than a ton of rock.  Rocks that size burn up in the atmosphere several times a year.  
> **username_0**: More mass than the satellite can still escape from the asteroid from the collision given that all the fragments go slower right?  
> **username_5**: @MiltonTheMeme, "slower" isn't enough.  In order to hit the Earth, you need the fragments to slow down to a near-stop; anything less, and they'll either end up in Earth orbit or continue back into interplanetary space with the rest of the asteroid.  
> **username_1**: @Mark [+1] and  *Thanks!* Ideally that could be moved to the answer post itself where future readers will be sure to see it. May readers (and "scrapers") ignore comments, and in Stack Exchange comments are by definition considered temporary and might disappear at any time (though that doesn't normally happen in practice).  

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