Why is NIRTON SYSTEM a Red Zone in "District 268"?

[GJD]

IIRC, radioactives tend to be concentrated in the core, and then in the crust, but not so much in the mantle. So it'd be a bit odd if it's a Mercury-like world that's lost its upper layers but still hasn't exposed its core, because you should be seeing mantle material exposed on the surface (or at least very close to it). If we're seeing the core, then it's a ridiculously huge core given it's size 6.

Radioactives are generally concentrated in the crust, since they appear as part of a homogenous melt in the mantle. It's not until they reach the surface that they will crystalise out and be concentrated.

That said, stripping off the crust of a planet will result in a new crust forming as the top layers of the mantle cool and dissasociate. The chemistry would be different, but you'd still get crustal processes forming.

G.

 

[Rikki Tikki Traveller]

But wouldn't the newly formed crust have a higher concentration of radioactives than the old crust had?

 

[GJD]

Hot necessarily. The abundance of fissionables in the mantle is no higher than in the crust, they are just more concentrated in the crust, so you get more in one place. Depends on the rapidity of the crustal stripping and the abundance in the melt. It's mostly the pressure of the crust and mantle that keeps the underlying strata fluid through geostatic pressure, rather than radiothermal heating (so it is thought) so a higher concentration of fissionables would possibly result in a higher internal temperature, meaning the mantle would remain fluid once the crust is stripped away. You could end up with seas of frozen magma, pretty much undifferentiated, with giant lumps of native mantle floating (pegmatite, sepentine etc) about in them. Volcanic eruptions might be common as the mantle hydrostatically re-adjusts itself. Think Mustafar from Star Wars or Io on a really bad day.

G.

 

[EDG]

Radioactives are generally concentrated in the crust, since they appear as part of a homogenous melt in the mantle. It's not until they reach the surface that they will crystalise out and be concentrated.

Oh yeah, you're right, I was getting my lithophile and siderophile elements muddled up. Th and U are lithophiles (at least according to this table: http://www.earth.uwaterloo.ca/services/whaton/waton/5a.html ), as are Rubidium and Potassium. Looking at that chart, I didn't realise that most of the left side of the periodic table was lithophile, the middle was mostly siderophile, and the right side mostly was chalcophile (and atmophile).

That said, stripping off the crust of a planet will result in a new crust forming as the top layers of the mantle cool and dissasociate. The chemistry would be different, but you'd still get crustal processes forming.

That's why I said "(or at least very close to [the surface])" .

 

[MJD]

True but boring answer:

Neil Frier did that bit of BtC. I have no idea what he had in mind (if anything) as a reason.

I personally find Neil's take on Traveller a bit too Star Trek for my taste (to put that differently, I wouldn't have done Nirton like that unless I was going to do kind of Ancients thing, which he might well have had in mind for all I know).

Some time ago, for a different project, Marc Miller told me to go with BtC if I felt like it, or to over-write it if I came up with something better.

For Spinward Marches I mostly ignored BtC but used the same source material. If something is in BtC but not mentioned in Spinward Marches then it's the same, or it's different, whatever you please.

So... Nirton is red zoned. The Marches book says so, so we know that's true. Everything else should be treated as a rumour overheard in a spacers' bar...

 

[Rikki Tikki Traveller]

Yeah, but my buddy Englii swears that he saw the scout report on Nirton that said it was crustal reformation after some ancient catastrophy. Englii is an honest guy, except when he plays cards, so I believe him.