On 4 Jul 2020 at 17:08, Timothy Collinson - timothy.c wrote:

> We're on Yebab https://wiki.travellerrpg.com/Yebab_(world) so not a
> huge amount of detail there (or anywhere else I can see) and I wasn't
> able to find much on the web aside from about Europa and Titan.
>
> I've looked at 'Exotic Atmospheres' in JTAS [Mongoose] 2 which itself
> is based on the JTAS [GDW] 17 special supplement on Exotic Atmospheres
> and the couple of short paragraphs therein help a bit.
>
> - the wiki says Yebab is 'chilly' but for a methane atmosphere world
> with methane lakes wouldn't have to be pretty much 'frozen' - i.e.
> very low temperature - or could it be warmer than I imagine?

Others covered the temp bit.

I'll also note that to *have* a methane atmosphere, it either has to
be far out in the system or have a really small star.

That's because solar UV will "crack" molecules in the upper atmsphere
leading to methane turning into methyl radicals and free hydrogen.
They'll recombine eventually, but unless the temps are really low the
hydrogen ions will be travelling above escape velocity and thus
wander off into space. And you'd also get OH and O radicals lathcing
onto the methyl radivals to form things like alcohol and the like.

That's how earth's initial atmosphere of methane, ammonia and water
converted into CO2, water and nitrogen. And then algae evolved and
started converting CO2 into oxygen.

Anyway, Titan is an example from our own system.

> - so is lighting up the Harrier's engines a problem in such an
> atmosphere, or is it just 'antigravity' all the way?   (but see next
> question)
>
> - and on a related note we had an (Aussie inspired) tour guide out in
> the 'bush' pointing out that lighting up a bbq "outside" wouldn't be a
> good idea?  Or am I again misunderstanding the nature of the
> place?   (JTAS 2 does talk about sparks and explosions but only
> where there's free oxygen which it says is unlikely.)

Yup. Though Alan E. Nourse's book "Trouble on Titan" had an
interesting idea for a vehicle. A jet plane designed for Titan. Itr
used oxygen for fuel to burn in the methane atmosphere.

> - speaking of bush, would flora and fauna be Earth normal 'analogues'
> so I can just use animal tables as usual and have at it as I wish with
> plants etc, or would the conditions/atmosphere dictate something very
> radically different?  (I could find nothing on this in my SF writing
> books which were pretty limited for such exotica)

This is the biggest problem. It's hard to come up with sufficient
energy for *active* multicellular organisms. They'd have to use
photosythesis to produce oxygen, but that'd likely be retained by the
plants, as they'd want to get energy by combing it with methane or
CO2 to create sugars.

Being that having a methane atmosphere *requires* low solar enery,
that makes photsynthesis a really slow process. And a lot of surface
area to absorb enough light to produce much food.

This means animals would have significant problems too.

If they aren't using photosythesis as the base of the food chain,
then it'd have to be chemosynthesis or something *really* weird like
radiosynthesis (using hard radiation as an enerfgy source).

> - I'm presuming that just as Harrier crew can operate on Yebab's
> surface in vacc suits, so an Ebokin in its equivalent of a vacc suit
> could operate in the Harrier's ATV as guide?

Actually, the temperatures would rule out simple vacc suits. You'd
need something like the gear they user during winter at the south
pole over the top of the suit to keep from freeezing to death.

Likewise, the natives couldn't handle the temps inside human craft.

> - I merrily bunged onto a regional map 'mines' and a 'penal colony'
> (which was a former mine) and a ruined town.  Happy enough with a
> ruined Ebokin town from way back, and decided a prison must be
> reasonable given the Ebokin love of regulations, law and a relatively
> high law level.  But what might they have been mining?  I said
> hydrocarbons laid down in the atmosphere over years but the mines
> abandoned because it was not really commercially viable as it was
> cheaper to just extract them from the atmosphere, but a) was that a
> possibility or was the database misinformed(!) and b) is there any
> reason it couldn't have just been your usual run of minerals etc?

The minerals would be similar to those on mosty planets, with the
exception that lack of oxygen, means you wouldn't have iron deposits
because you wouldn't hasve dissolved iron in water that later got
precipitated out when oxygen became common thus forming most of the
non-meteoric iron deposits.

Big advantage for the natives is that many minerals can be smelted
just by heating them in "air". That works for oxide minerals. Rather
more difficult for sulfide minerals.

And "fire" would be moderately advance tech unless the local plants
have ridiculous amounts of oxygen in them.

> - a "tropical methane storm" is moving in which I pinched from Titan
> (or was it Europa?) but the wind speeds mentioned seemed very very low
> (i.e. so low as to not be threatening) but I've assumed that that's
> due to a lack of much of an atmosphere.

Titan. Europa lost its methane and ammonia long ago. More to cracking
caused by the high energy radiation around Jupiter.

And Titan's atmosphere is pretty thick.

> Whereas on Yebab with a size of 9 I'm imagining a much denser
> atmosphere - although technically atmosphere A doesn't give any idea
> of actual density despite it feeling as if it should be thicker than
> a '9'!  Does anyone know what kind of parameters (size, wind speed,
> other) I can reasonably have this storm at?  Or just use it as an
> analogue for a cyclone/typhoon moving in?

Well, it'll likely be fairly dense, say at least as dense as earth's.
But because it *has* to be getting less solar energy, that should
moderate the weather some.

But possibly not.

--
Leonard Erickson (aka shadow)
shadow at shadowgard dot com