I need some help with a couple of the planet building theories I’m playing around with. I’ve looked up most of this stuff and can follow the physics if given the time (and instructional tutuorial help book) so if possible can you provide a laymans answer for a quick read and the links to the physics so I can work out the numbers later?
As far as possible, the planet is earth sized if maybe slightly smaller, similar gravity, distance from the sun, atmosphere, it has two Moon's outside the Roche limit (one large, one small) etc. It is in the goldilocks zone, supporting complex life, thankfully. Unfortunately it is prone to periodic meteor showers and not always the pretty kind. It has the scars to prove it. Oh, and just to be cliché, it has planetary rings (with a few tiny shepherd moons)!
The main idea I need to keep for my story is periodic bombardment from the same source. The rings are optional, if it really isn’t feasible. However, I would really very much like to keep them as currently they are the source of my story.
Most of the settlements I want to affect by the bombardment are around the equator and low-mid latitudes. I’m working on the premise that it’s normally just a pretty sight in the sky but occasionally one or two larger events occur. And every few centuries several make it through causing chaos in the lands below. I’m very destructive! FYI not extinction level events. I’m not that destructive! Merely a few shattered cities, accidently crashing into (probably be safer to crash near rather than into) a volcano setting off a small localised lava flow, breaching natural sea walls, tsunamis and the like!
Reading up on my physics and your previous posts about planets with planetary rings, earth sized planets don’t have the gravity to maintain a ring system for any extended period of time (geologically speaking). Any small dust particles/rocks/ice that make up the thin (10-100m thick) ring within the Roche limit will ultimately end up either falling to the earth type planet or flying off into space.
So if I want the rings to exist for at least 2-3 thousand years preferably longer (e.g. 10-20 thousand years...) with some sort of periodic bombardment?
I have two possible theories:
(1) The planet’s orbit takes it near/through the very outer reaches of an asteroid belt region producing spectacular annual or decadal displays (think Anne McCaffery’s Dragons of Pern series of Thread or Stargate’s Hundred days episode – not the best but you get the idea). Could a periodic immersion in the outer dusty reaches of an asteroid belt, resupply the ring system or would that just wipe out the whole thing altogether?
(2) If an asteroid belt doesn’t work, could it be the trail of a comet tail with a large but regular orbit (more frequent than haley’s comet and much closer) that gets caught up to form the ring system?
The way I see it both these theories allow for periodic bombardment by meteor showers/comet tail fragments of the size of Tunguska 1908 event and slightly bigger to occur.
Which is more likely?
One image I have in my head: Could they dive through the rings and still hit home?; Leaving a huge tear in the ring for years to come until rotational effects and resupply by asteroid belt/comet tail fill in the gap. I wouldn’t expect every event to hit the rings, just every couple of centuries or so.
Thanks for any help!