The Black Goo & Crowd Control?

Ridley speculated that the xeno has a very short lifespan, so if that goes for all the versions of the pathogen, once it infected and killed all the localized life, say on an isolated continent or isolated region on a continent, it may not necessarily spread across an entire planet.

Ridley also speculated that it would travel like a plague and spread everywhere so that within a year all fauna would be gone.

I suppose it all depends on which variant of the pathogen the Engineers dropped and what they were trying to accomplish with it.

@Kethol - Yes, I was hoping to find out more about the effects it had on Planet 4, like how far away were animals & plants affected?  It definitely did a bang up job on the Humanoid arena & surrounding city.

@Kethol

That makes a lot of sense about Xenos having a short lifespan, so then Engineers can them to wipe-out fauna and start again.

But, in the Covenant novel David says that the pathogen can remain dormant indefinitely, so it seemed like a kind of salt-the-earth type weapon.

Do you think maybe the Engineers have some kind of planet-wide antidote to neutralize the pathogen? 

Cerulean Blue, that is a very interesting idea but the pathogen seems like a difficult thing to use to wipe out populations of single continents, the risk of it spreading to unintended populations seems pretty high.

But, if they do have some antidote to neutralize the pathogen on other continents or to prevent it from spreading I think it might work!

No, Ridley Scott said a "few canisters" would be enough to wipe out a whole planet within a month. The chain reaction is just so powerful. 

Its a nice theory and who knows..

It depends on the idea of WHAT the Black Goo and its affects in relation to the Sacrificial Goo we are shown the Sacrificial Scene will ultimately lead to all/most life on a World Evolving from the result of this and so the effects eventually spread World Wide but this process would have taken Millions of years.

The comments by RS over the years regarding the Black Goo seems to indicate that a Large Cargo of them would wipe out a Planet.

Alien Covenant it appears to have wiped out all LIFE apart from the Plants and also had mutated/evolved some kind of Fungi/Mold to become the Spores.

But then how does David obtain any organisms for his experiments, so this is a Potential loose End where at first when the Trailers came out i wondered if the Cathedral was some kind of Noah's Ark and inside it is safe from the effects of Outside and it contained samples of Life Forms so they can repopulate after a Disaster...  At this time however i was wondering was the Disaster Scene a Ancient Events which it now is not..... and so its still open to debate as to how David got Specimens for his Tests as NOT-ALL-LIFE was killed off, but then it appears ALL-LIFE locally to the City has no Life, but does that mean the whole World does not?

"Do you think maybe the Engineers have some kind of planet-wide antidote to neutralize the pathogen?"

This is what i thought again after the Trailers, that maybe the Cathedral Dome Gold Device releases a Engineer Weapon that basically fries all Genetic Life and thus Halts the Infection of the Black Goo... which is why i wondered was the Cathedral some kind of Noah's Ark.

After seeing/hearing about the docking Juggernaught and Davids Bombardment i then wondered does the Scorpion-ship release some Engineer Weapon that prevents the spread of the Black Goo and this Weapon Release is what caused the Juggernaught to Crash.

But since the movie i have a explanation of the Black Goo being different due to it being kind of like a Nuclear Weapon where the Black Goo is like the Radioactive component and so has different effects depending on contact with the Radioactive component, well the Black Goo in this case and so the Weaponized/Activated Urns in a Bombardment has a Reaction that changes the Black Goo effects to mainly Kill off Genetic Material like how a Nuclear Weapons, Uranium/Plutonium is a Reactive Element that causes the wide spread Death/Explosion....

Compared to a different effect if you was to come into contact with the Elements inside before the Weapon is Primed and Activated.... so if you touched Uranium/Plutonium or Black Goo Canisters Contents...  compared to the effects when these Elements are activated in a explosive Bombardment.

@BigDave - Like an organic nuclear weapon? 

Very interesting.......