Hi there

Many thanks Tim, this is really helpful.

> On 24 Nov 2014, at 12:07, Tim <xxxxxx@little-possums.net> wrote:
>
>> On Mon, Nov 24, 2014 at 10:07:04AM +0000, Timothy Collinson wrote:
>> Triton orbits in the equatorial plane of Neptune which made me think
>> that from the surface of Triton, Neptune would appear 'horizontal'
>> as usual.  Am I missing something?
>
> It would depend upon where you're viewing from.  Near one of Triton's
> poles, Neptune's equator (and weather bands) should appear horizontal:
> i.e. literally "aligned with the horizon" of that location.

Ah ok

>  From many
> places around the equator they would appear vertical.

Brilliant, so I could have either.  Marvellous.

>  From much of
> Triton's surface, Neptune would never be visible at all.

"Much"?  Is it not simply 'half'?

>
>
>> OK, so can I just double check that the only thing that would affect
>> where Neptune is in the sky is the location of your base?
>
> Yes; Triton's eccentricity is minuscule and so it doesn't even have
> the libration that our moon does.
>
Hence my half above?

>
>> Would anything of Neptune's rather paltry (I understand) rings be
>> visible from Triton?
>
> Yes, I'm pretty sure at least two of the rings/arcs should be visible.
> They all lie well inside Triton's orbit, and are very nearly in the
> plane of Neptune's rotation.  Triton isn't, so its orbit would take it
> above and below the rings during its 6-day "month".

Ok.  Between this and Richard's answer I'll have them visible.  Not that it's very crucial, just umm, well, atmosphere as it were. :-). Of course it might be fun to mention its dependence on where on its 'month' it is.  Nice.  Thank you.

>
>
>> Am I right in thinking that the gravity figure for Triton given in Orbital
>> of 0.78 is wrong and it should be 0.078 G?  (I.e. PCs from Luna would find
>> it lighter than home, but not that much).
>
> I don't have the reference, but the units may be the SI unit m/s^-2
> instead of gees.  If so, it's correct: about 0.08 gees.

Yes, that can't me for a moment but it was definitely referring to G and had the Moon (ie Luna) as 0.16 G.

>
>
>> Using something like the Palomino Heavy Lander (p.72) of the setting
>> (i.e.  no anti-grav) what are reasonable transit times from a base
>> to, say 100km away, 1000km away, somewhere on the opposite side of
>> the moon?
>
> Sorry, I'm not at all familiar with the setting or the performance
> characteristics of the Palomino Heavy Lander.  I presume it can easily
> land on Triton, and so must have at least 1 km/s delta-V at 0.1 gee
> thrust or so.
>

I don't think the book gives that kind of detail although I'll look again.  (That was the kind of thing I was looking for).

> So at most 10 minutes would be needed to travel 100 km, not including
> pre-boost preparations and landing details.  No more than 30 minutes
> for 1000 km, and something like an hour for the other side of the
> moon.

But that's really helpful, thank you.  At least it gives me a ball park figures (my guesses were too long)...

>  Reduce the times if the lander's performance greatly exceeds
> the minimum.  Increase them if they need a lot of pre-flight checks,
> very careful selection of landing site, or other complications.

... or maybe I'll put in the preflight checks!  Cheers

>
>
>> Are these three components thoroughly mixed rather than patches of
>> one and clumps of another?
>
> Lots of clumps and patches.  Images show the Triton has a rather
> interesting differentiated surface.

Yes, what images I've found are pretty interesting and attractive.

>
>
>> Would the Nitrogen geysers simply be venting the Nitrogen to space
>> or would it (or some of it) fall back to Triton as Nitrogen "snow"?
>
> Almost all of it would fall back.  Triton has a fairly thick
> atmosphere by the standards of moons; a few kilograms per square
> metre.  It has tenuous clouds, but I'm not sure if they'd be visible
> without sensitive instruments watching starlight through them edge-on.

Ah, that answers that question about the clouds I'd read about.  I didn't quite imagine that they'd be the white fluffy things of Earth!

Sounds, however, if there's enough wiggle room for a bit of fiction if desired.

>
>
>> If there was a sub-surface ocean on Triton (I'm assuming this means
>> liquid not frozen) are we talking water or something else?  (I'm
>> presuming that if it was liquid water it would be warmed from frozen
>> by the 'solid greenhouse effect' of the frozen Nitrogen (etc)
>> above.)
>
> Yes, liquid water mostly.  Almost certainly with some ammonia and
> other stuff in it.  It would most likely be kept liquid from decay of
> tiny amounts of radioactive elements present in rocks.  Triton's
> density requires that it contain significant amounts of denser
> material than ices, so it almost certainly has such elements present.
>
> Solids are very good insulators on planetary scales, so even very
> tenuous sources of heat like that can keep the interior very much
> hotter than the surface.  The surface temperatures are dominated by
> inward and outward balances of light and heat radiation, and Triton
> gets very little light indeed.  Easily enough to see with (comparable
> to indoor artificial lighting), but not enough to keep the surface
> warm against the black heatsink of space.
>
Ah, that's helpful as well. I was rather assuming there was some light available.

It does occur to me to ask as well, if I may,
- would the frozen Nitrogen layer sit on the rock or water (etc) below, or would there be any kind of gap (I'm specifically thinking human sized!)
- roughly how deep is the Nitrogen layer?
- how long would it take to drill though (I'm thinking of a hole wide enough to take a human sized capsule)?
Or are we now in the realm of make up something that sounds reasonable?!
Essentially I'm looking at PCs checking out the regular 'hot spots' beneath the ice that have been discovered.  Not quite yet decided whether they should be natural or of alien origin or what they'd actually consist of in either case.

Thank you again for the pointers.  Really helpful.
tc