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.  From many
places around the equator they would appear vertical.  From much of
Triton's surface, Neptune would never be visible at all.

> 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.

> 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".

> 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.

> 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.

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.  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.

> 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.

> 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.

> 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.

- Tim