Celestia Forums

I know that marcury has a very big core, and a thin surface.
Does anybody know why?
I have herad that maybe in the past the planet was much bigger, and that a big asterodi crash on it, and most of teh surface went out. but if that is what happened, where are all those rocks??? maybe they went to the sun.
I dno't know. what do you think??

I've never heard that before, i better start watching more of the Science Channel

-Shadow

today at night i will see again the program called SPACE. in the bbc world channel. I am at +3, and the program is at 2:00 am.

How old is that program?
I saw something similar on BBC world about Antimatter when i was in Finland. It was very interesting though I don't remember what it was called
it may have been SPACE.

the program is conducted by Sam Neil, the one that acted in jurasic park

I haven't seen that movie so I don't know who he is,
What time zone is argentina in? GMT - 6 or -7?? Is it a daily program or a Weekly program? I might have BBC somewhere on satalite

1) he also was in other movies.
2)Argentina is in GMT -3
3)I'm from argentina, but I'm not living there.
4)I dont know if its weekly or daily. I saw it an Friday night, and today at night I'll see it again.

Oh then where are you right now?
I wanted to know what time it would be on for GMT-5

I prefer not to say where I am. Lady Hawk knows, so ask her if you want to know.
But im can tell you that here whe are in GMT+3.

btw, i think that we are only talking about the tv program, and not about my question

o That means it's on a 6 PM for thank's Maybe they'll replay the spiosde sometime andI'll have something to say.

I also vaguely remember seeing something about an impact that ripped most of its mantle off. It would have been very early in its life. Maybe around the same time Orpheus hit the Earth.
So let’s add this up. Possibly Mercury was struck by something big enough to rip most of its mantle off, Venus was hit hard enough to flip it over on its north pole, Earth was hit by Orpheus and the moon resulted, Mars was hit by something very big that created the Hellas basin and pushed up the Tharsis rise and also created Vales Marineris. And all these things can be narrowed down to close to the same time period. What the hack was going on in our solar system to cause all these massive collisions 4 billion years ago. I mean these were big events. Not your average collisions by a long shot.

Don.

Don. Edwards wrote:What the hack was going on in our solar system to cause all these massive collisions 4 billion years ago. I mean these were big events. Not your average collisions by a long shot.

Don.

For the time, they were the average collisions... Don't forget, you didn't originally have four planet-sized orbiting the sun, you had maybe a dozen or so objects between moon-sized and Earth-sized, because all the small planetesimals that made the planets had been mopped up by then. The four planets we know today are the survivors of this epoch - the rest got either ejected from the system (there's an interesting paper on this at http://www.gps.caltech.edu/faculty/stev ... lanets.pdf ) or smashed into the ones that survived til today and were absorbed by them.

I knew that, I guess I should have stated it differently. What I was trying to get across was that these events were quite literally Earth shattering events. I mean sure we all know that things were very crowed in the beginning but the evidence is starting to show that things calmed down enough for the planets to form crusts and to really start evolving. Then wham, all of a sudden all four terrestrial planets get slammed. I don’t think it happened all at once but it definitely looks like it happened just a few million years apart. I guess we have to say that the early solar system was also a very unstable place to be. The planet ejection theory is interesting and I have heard of it before as well. Might it be possible that some planet sized objects might not have been totally ejected? I mean how hard would it be to find lets say a Mars sized planetoid roaming the out Kuiper Belt or the Ort Cloud. Maybe some of these objects are now on orbits like comets but now they take hundreds of thousands of years to make an orbit. I am not trying to start one of those lame doomsday theories but what are the chances that some of our smaller sister worlds are still around just waiting for us to find them? Just think of the things they could teach us of the early solar system.
I also forgot to add Uranus to that list. As it looks like something the size of the Earth hit it as well and turned it on its side. I mean stop and think of that. An Earth sized planetoid found its way out to Uranus and hit it. Now that would be something to see as well. A saw another documentary a while back were they animated that. It was quite interesting to see how the moons orbits all shifted and they showed several of them colliding in the process of orbital reorientation. I guess they got that idea because so many of Uranus’ moons look like they were broken and then put back together. Darn I wish I could remember the names of all these programs. I have seen so many of them over the years.

Don.

I'm not sure exactly how they get ejected - presumably by getting jostled into orbits that send them close to Jupiter or the sun, which flings them out? So I'm not sure if you can have an 'almost ejected' object, it may be a case of 'either it's ejected or it isn't' (in which case it crashes into something).

As for Uranus, I thought the 'broken up satellites reforming' idea was what they came up with to explain Miranda's patchwork terrain just after the Voyager 2 flyby in 1986, but it's since been discarded. I may be wrong though. I definitely remember seeing 5the animation you're thinking of, but I'm sure it was quite a while ago. Current theories about Uranus' (and Neptune's) formation are that they took longer to form than the rest of the solar system because their orbits are so large, so it's not hard to imagine an earth-sized planetesimal forming out there and smacking into Uranus late in its formation.