In need of a major desaster

[Reynard]

Duh, misread your original premise that this is a water world so life, literally, never left the oceans! Low vulcanism also means a super volcano, even an underwater one, would be very unlikely. The low tectonics can also explain no real landmasses above sea level.

Since there's so much algae, that suggests something targeted higher lifeforms on the vulnerable ocean surface level. How about a very virulant version of a worldwide 'red tide' that destroys the food chain above the algae and maybe plankton level. Sealife far below is spared and maybe have a slightly different body chemistry because of living conditions to make them immune when the contaminated matter sinks. After whatever time frame the 'red tide' goes away leaving no trace and a mystery as to why there's only higher life forms so deep. Evolution will need a lot of time for life to adapt back to the surface.

 

[locarno24]

Thalassa

Classic. Have an official Arthur C. Clarke cookie.

Wiping out life on the surface without affecting deep sea is probably best done via something in the atmosphere. The trick is to pick a poison which can't translate into the water (or which doesn't last long if it does) - seeding the atmosphere with alpha-particle emitting dust is one option - either by a weapon or by asteroids. The latter needn't be big; you don't mind and indeed might actively want them to burn up in the atmosphere. Of course, it's all decayed by now.

Actually, scrub that. The problem is how deep is deep - the idea above wouldn't get the upper sees more than a very short way into the water. Radiation pulse, as suggested, might work, but it has to be prolonged enough to last a whole day without getting through to the depths. The problem with stellar events is that they're reasonably easy for a starfaring race to track down supporting evidence for.

 

[AndrewW]

You know, he's probably just gathering ideas for his next attack on the 3rd Imperium, he wants to disrupt as many planets as he can so that it will fall apart...

 

[rust]

Again, thank you all very much for your ideas.

I guess I will go with the satellite in the star's corona which triggered
a superflare, leaving open whether this was a failed experiment to
increase the star's luminosity as part of a terraforming plan, a weird
defense mechanism or just an accident.

The superflare wiped out almost all of the plankton (algae, etc.) at or
near the ocean's surface, the food chain of this part of Thalassa's oce-
an collapsed, and all higher life forms of the surface biosphere became
extinct.

The genetically manipulated deep sea life forms, introduced by the ali-
ens and forming their own ecosystem, mostly independent from the one
of the surface creatures, were reduced in numbers, but lost only few spe-
cies because of the event.

After about 4,000 years, when the colonists arrived, the algae etc. on the
ocean surface had recovered, but the time was too short for higher life to
develop again. Down in the deep sea, the ecosystem of the deep sea crea-
tures has stabilized, but the predators have not lost their ability to hunt
near the surface, too, and "welcome" the fish introduced by the colonists.

A chain of discoveries, spread out over several years of game time, will
lead the colonists to the information that the aliens left the planet imme-
diately after the superflare, and that the satellite responsible for the de-
saster is still in the star's corona, and possibly still active. It should be
found and if necessary deactivated, but moving around in the corona of
a star is an unpleasant task - perfect for player characters.

 

[rust]

You know, he's probably just gathering ideas for his next attack on the 3rd Imperium, he wants to disrupt as many planets as he can so that it will fall apart...

No, I think the Imperium is now safe, I have given up on it.

The Thalassa setting will use a slightly modified version of the
Babylon 5 universe as its background, one with fewer intelli-
gent species, and fewer of those of the humanoid kind.

The five years of the series provide just the kind and number
of offworld background events to keep the colonists (un)happy,
and with the semi-aquatic Abbai at one end, a dictatorship on
Earth at the other end, and lots of interstellar wars in between,
this is a nice environment for a "water world colony saga".

While the events will be from Babylon 5, the game system will
be a version of BRP, and the technology will be from GURPS.

So, really, you can tell Strephon that his Imperium is safe now.

 

[Rikki Tikki Traveller]

How about turning the disaster on it's head.

The planet was terraformed in the past. That Terraforming created the life forms the currently reside in the deep.

The Terraforming Failed.

Surface life died off as the planet reverted to its natural state, but SOME of the deep sea lifeforms survived.

Later ANOTHER race comes along and begins terraforming the planet for themselves; completely unaware of the small biosphere in the deep oceans, surviving by scavenging around a ridge of sea vents. Only a few dozen species, nothing bigger than a fingernail. The new race was much more successful at terraforming the surface and it is now stable.

Along the way, the deep sea life forms evolved and grew with the new food source from the surface.

I know you are using the B5 background as a basis for your setting, so I offer the following:

One of the previous round of Younger Races did the initial terraforming, but was destroyed before it was complete by the Shadows. A new Younger Race did the second terraforming, but was destroyed during one of the more recent Shadow Wars, maybe 100,000 years ago (ish).

So the planet has basically been on its own, surface and deep life evolving for the last 100,000 years. Now the humans arrive and find the 2 different biospheres.

 

[AndrewW]

Again, thank you all very much for your ideas.

I guess I will go with the satellite in the star's corona which triggered
a superflare, leaving open whether this was a failed experiment to
increase the star's luminosity as part of a terraforming plan, a weird
defense mechanism or just an accident.

Hmmm, you've given up on the Third Imperium yet you are importing the Darrians...

 

[rust]

How about turning the disaster on it's head.

Thank you for this idea, I will think about it.

It would be an interesting way to give the setting a longer (pre-)
history, but I have to see how well it connects with my other ideas
for the setting's distant past, and this is still very much a work in
progress.

 

[rust]

Hmmm, you've given up on the Third Imperium yet you are importing the Darrians...

Actually, no. My idea of a satellite in a star's corona which in-
creases the star's output and causes a desaster is much more
influenced by the Perry Rhodan series, where a species named
Cappins deployed such a satellite around the time of the Nean-
derthals. The satellite became active again several thousand
years later, and the only way to get rid of it was a time travel
mission to the distant past (but no time travel for me).

Here is a nice picture of that satellite:
http://www.pr-materiequelle.de/begriffe/riss/risszei/r500.htm

This thread has just reminded me of this, and also of the option
to "borrow" some of the details from the Perry Rhodan series, to
avoid to have to invent the wheel once more.

 

[zozotroll]

I know coming in late.

I like comets. so here is an idea I have held for some time, but never had the right moment to use it.

First off as a water world small chunks are not going to make any craters at all. So a large comet gets the Shoemaker-Ley treatment and comes in as a stream of debris. Perhaps ever got broken twice, once made it big peices, the second time it passed a second big body and the peices got busted up.

I majored in History, not science so I have no idea if you can break something up without sucking it into the big body itself, but if i s crumbly enough it should work.

What you wind up with is a cluster bomb that comes in over a period of sme days. no big impacts, just lots of little ones.Plenty of stream ad stuff keeps getting back into the air to really block off sunlight to the surface. I dont know if that is enough to do in a full eco system by itself, but it just cant be good for it.

Owen

 

[Rick]

I majored in History, not science so I have no idea if you can break something up without sucking it into the big body itself, but if i s crumbly enough it should work.

If it hits the outer atmosphere at a shallow enough angle, it can 'bounce' back into space (it's a bit like skipping stones across a pond); if it bounces hard enough it could break up.

What you wind up with is a cluster bomb that comes in over a period of sme days. no big impacts, just lots of little ones.Plenty of stream ad stuff keeps getting back into the air to really block off sunlight to the surface. I dont know if that is enough to do in a full eco system by itself, but it just cant be good for it.

The steam wouldn't block out enough of the sunlight to cause a single ecological disaster by itself - it would be like having a succession of cloudy days. However, with that much more water vapour in the atmosphere, it would definately increase the cloud cover for a long period, which would cause an increase in temperature, for however long it took for the water vapour to return to the surface.

Ok. Cloudy days with lots of rain, then.

I suppose if the comet was mainly sulphurous, you could get dilute sulphuric acid falling as rain all over the planet, that wouldn't be healthy!

 

[Jak Nazryth]

I just thought of something reading several posts.
What if the planet was pummeled by a massive amount of comets, and is why it became a water world. Maybe there are ancient civilizations deep under water that used to be high and dry. Maybe the ocean level rose an average of 200-300 meters or so because of not one gargantuan comet, but a cluster of smaller comets, (that at one time was a huge comet which broke up into smaller sizes upon entering the gravitational pull of the star)?
You mine the ocean floors for rare metals? Who says these metals aren't resulting from a previous advance civilization? Maybe you can discover ruins during the mining/ dredging?
Just thinking out loud.

 

[rust]

Thank you for your ideas.

They are on my list, and I will see where and how I can use them.

 

[Reynard]

Here's another one that explains a few things.

Your system has a large quantity of icy bodies in one or more asteroid belts. Like the Sol system icy bodies are what gave Earth its water as it cooled enough to hold water. Earth's tectonic activity makes for highs and lows as the crust twists and turns, bucks and crumbles. Water filled the places inbetween. Your world has very little activity so there's much less topography. Let's say though that early asteroid bombardments left impact craters that would not wear down as fast even under water.

Originally there was some land masses and some life would develope there. The asteroid belt has an unusual gravitational influence with a high eliiptic gas giant so every some many eons ateroids are 'scooped' loose and may make contact with the world delivering small packages of new material mostly water. There is enough new water to raise the levels significantly each time. The impacts plus new fresh water with other possible contaminates tend to clean the top strata of higher life. The cooling effect of new icy water plus the fact there's little vertical current flow renews temperature extreme stratification. This slows older deep lifeform from recolonizing the surface. This would also create an excellent energy source using the extreme temperatures plus possible salinity differences.

The latest bombardment may have been hundreds to hundreds of thousands of years ago, The last land masses have finally sunk beneath the new waters and surface life has gone again leaving simple plant and animal life. The hotter closer sun encourages activity of algaes on the surface and deep animal life will take many eons to adapt again.

With exploration there will be evidence of land animals where there is no land. There will be fossilized strata of massive extinctions of surface ocean life well out of proportion to deepsea life. It takes a chilling turn as to how frequent it occurs.