Thanks a lot for this interesting post. I had read about the rocket story hitting the Moon in local newspapers, but I didn’t spend any time to investigate what it was precisely. From your blog, this is still something unknown. Do you confirm?
On the other hand, do yo know why the purple curve in the plot of the debris exhibits ups and downs? Is it because the associated debris re-enter Earth’s atmosphere and got burned? Thanks in advance for enlightening me :)
Cheers!
PS: I hope we will be able to clean the space at some point… Truly... Otherwise, this may soon be a real problem.
Thanks for passing by! Current evidence shows that the impactor is the last stage of the rocket that launched the Chang'e 5 T1, a sample return test mission of China that went to the moon (without landing) and returned to Earth landing on Mongolia in 2014. The spacecraft itself is a test for a real robotic sample return mission that could have the possibility of bringing back samples from our natural satellite. It is thought that the rocket booster that reentered originaly on Earth and was mistaken with this is from Chang'e 5, a mission that in 2020 successfully returned samples from the Moon.
So far it is a relatively common issue leaving last stages of the rocket on Space. If you think about it, you brought that last part of the rocket to orbit in orbital speed, so it is quite complicated to completely bringint it back. For interplanetary missions this is even more critical, we use this booster to put our spacecraft on a escape speed from Earth orbit, so the most common (and probalby only) strategy is abandoning this booster, just trying to avoid it inteferes with the current desired orbit.
Source: NASA ODPO with additional data from Wikipedia
Regarding the fragments, you are completely right, the number of fragments grows and decays when he objects reentry into atmosphere and burn. Objects in very low orbits decay relatively fast, while orbits above the 600 km (that is not crazy high) will remain in orbit for very long periods. I have added some "milestones" to the graph to explain a bit some of those big increases. They come from breakups on orbit, but also from spacecraft collision on orbit (with death satellites) and even some Anti Satellite weapon (ASAT) tests. The Chinese test on 2007 happend at around 800 km and the debris will remain on orbit for a while. Other US and India ASATs were around 350 km and the very last and renowed by Russia on Nov 21 was about 550 km high. A collision (voluntary or not) expells fragments to many orbital apogees, higher and lower, some of them will reenter faster than others
Source: Space Academy
I think i will try to put a little bit of orther in these thoughts and maybe it can be the main body for another blog post!
Thanks a lot for all these extra bits of information, especially for what concerns the second part in which I am super interested (I really enjoyed the annotated plot). I therefore definitely support the idea of having a dedicated blog on this matter!
Cheers!