Rings Around Earth From Ancient Meteorites

HorsePunchKid writes "According to an article on CNN (SNL version), ancient meteorites may have glanced off of the surface and shattered, causing rings around the Earth. These rings, which may have persisted for hundreds of thousands of years, could have had a profound effect on the climate in tropical regions, where the rings would block out light from the Sun. Still rather speculative, but the theory may help explain some patterns observed in the geological record. The idea has been around for a while, and some scientists are skeptical."

Comments

I still favour the fire theories...

[purduephotog]

Given a large impact that engulfs some 20% of the land mass in flame...

Said impact ejecta would be thrown up and into the stratosphere, circle, and land somewhere opposite (say 3/4) around the globe. More impacts, more fire. Lots of soot to block out light.

I can see a 'ring' of debris specifically targetting the tropics region, but i just have trouble dealing with the numbers of objects required to decrease the light that significantly resulting in a sphere of Earths size being cooled that significantly.

Suffice to say, the ring is there, but I'd still throw my support behind half the planet burning up as a more tangible reason.

Repost from Tuesday

[tbmaddux]

Look here.

about skepticism

[benploni]

> and some scientists are skeptical.

ALL scientists are skeptical. It's a basic requirement of the scientific method, and a reason it works wso damn well.

Can I be skeptical, too?

[shimmin]

I'm not a planetary scientist, but I'm still skeptical. So a rock gets blasted off the surface of the earth with some ballistic trajectory. Unless something acts on it near apogee to circularize its orbit, that orbit will return to the point it began (which lies inside the atmosphere).

So most of the rocks from such a collision will either be on an escape trajectory to become interplanteary debris, or secondary meterites that will fall over the next few days.

Where's the circularizing force in these models to put debris into long-term stable orbits?

Re:Can I be skeptical, too?

[mysticgoat]

Unless something acts on it near apogee to circularize its orbit, that orbit will return to the point it began (which lies inside the atmosphere)

No. The model of orbital mechanics that you are using does not contain enough objects. Here is a more realistic way of visualizing the process:

Instead of looking at one chunk of rock in a billiard-like model, think in terms of the spray of material that would be generated by a glancing strike (which is also the most likely kind). Most of the particles in this spray will not have orbital velocity and will rain back down, with the larger and faster ones making a string of secondary impact craters. A much smaller portion will reach escape velocity and become interplanetary objects.

But what is significant is the group of particles whose velocities exceed orbital velocity but do not reach escape velocity. That is a pretty wide range of speeds. At first these objects will also have a wide range of apogees and perigees, but they will mostly be in the same plane. Their own gravitational interactions and collisions will redistribute the kinetic energy of the group as a whole into a ring. In essence, the circularizing agent that you are looking for is the aggregate effect of the group on each individual member, a sort of gravitational peer pressure. Ring formation is probably a positive feedback process, where the proto ring's growth increases its influence on the remaining wild particles.

There are three ring shepherds that will cause any debris ring (any satellite for that matter) to seek an equatorial orbit over time: the Sun, the Moon, and the Earth's equatorial bulge. I imagine the Moon's presence would also assure that any Earth ring would be relatively short lived.

I would also think that any Earth ring formed in this way would be quite bright, at least for a while. I would think the ejecta stream would suck along a lot of air and water vapor through entrainment, and that many of the ring particles would be frosted as they cooled.

I'm not saying I'm convinced that this happened. But it is an intriguing scenario and might go far to explain ice ages and such. One of the more intriguing things about it is that it appears to be testable in several different ways.