Can the Imperium still terraform?

Question

During the DAoT, humans were able to terraform:

Percipre was once a famous garden world. Terraforming created a lush paradise, stocked with an incredible variety of plant species from around the galaxy. With the failure of the Terraforming Engines, the planet's population constructed vast glasshouses to protect the collections from the ever harsher conditions, and now only the hardiest of xeno-flora survive outside of their protection.

...

Terraforming: Percipre was extensively terraformed some time before Imperial records pertaining to the Calixis Sector began - possibly as far back as the Dark Age of Technology. Enormous machines provided a lush environment famed for its fertility. However, in a later age, the knowledge to maintain the Great Engines was lost, and the planet's inhabitants were forced to turn to more primitive means as their world's atmosphere began to leach off in to space. As a result much of Percipre's surface is covered by vast gas-tight glasshouses constructed from great panes held in ornate wrought iron frameworks. Within these gothic edifices, most large enough for a Titan to walk erect, row after row of foodstuffs grow in hydroponics beds, tended by massed ranks of faceless servitors.

From the article on Percipre on Lexicanum

It mentions that the knowledge to maintain the Terraforming machines was lost. But with how vast the Imperium is, this does not necessarly mean that the knowledge is lost in general. It may simply be that the Mechanicus considers this world not important enough to dedicate specialized adepts and magi to maintain them.

Does the Imperium still have the knowledge to create and maintain Terraforming machines or has this been utterly lost?

Answer 1

Yes, technically

So in the Rogue Trader and several other sources up until around 5th ed ( I don't have my books in front of me) Terraforming was still a thing. Mechanicus "Terraforming Battalions" would be dispatched to a given planet/moon for a few centuries to tidy things up for use. However this doesn't seem to be "Take barren rock and make it a garden world." It's more "take a hellworld and make it JUST livable enough to put a forge on." Or "Tweak this planet JUST enough that it can farm Grox."

There are also numerous worlds, like some other posters have mentioned, that have Terraforming machines which keep the atmosphere or geology of a planet stable. These tend to be described as pre-Crusade tech in the fluff, but I think that's an artifact of storytelling rather than a "usual" aspect of the universe. After all, it's WAY more interesting if a perfectly-habitable world's terraforming fails and it quickly becomes a barren desert/volcanic hellscape compared to a world where the terraforming means the place goes from "annex of hell" to "main lobby of hell"! Given what we know real-world of terraforming most of those "turned uninhabitable rock into something sorta workable" projects the 40k mechanicus can still do would also need some sort of continual maintenance.

To the best of my knowledge (I've turned almost exclusively to 30k post-great-rift/return of G-man) this fluff has not been retconned. But there's been some wild changes in the last couple years.

Answer 2

I am as yet still to find the reference(s) that can verify this, but to put it simply: yes, Terraforming is till a thing, but it is nowhere hear as effective as it once was, and even then, while it was effective, it wasn't very efficient.

From the Lexicanum:

Terraforming created a lush paradise, stocked with an incredible variety of plant species from around the galaxy. With the failure of the Terraforming Engines, the planet's population constructed vast glasshouses to protect the collections from the ever harsher conditions, and now only the hardiest of xeno-flora survive outside of their protection.

[...]

Enormous machines provided a lush environment famed for its fertility. However, in a later age, the knowledge to maintain the Great Engines was lost, and the planet's inhabitants were forced to turn to more primitive means as their world's atmosphere began to leach off in to space. As a result much of Percipre's surface is covered by vast gas-tight glasshouses constructed from great panes held in ornate wrought iron frameworks.

This implies that the Terraforming was not a permanent process, but more of a maintainable solution.

There are sloe several discussions talking about this online and while they don't reference anything specific, they all do same the same thing: Terraforming is still a thing, but is far less powerful, taking thousands of years to work.

1. Yes they do have the technology but it’s not very good and it takes them several thousand years to do it.

2. The Adeptus Mechanicus still seems to possess some knowledge of terraforming, but it has become inefficient and unreliable.

3.

Do they have the tech to take a dead world and terraform it until it can support life again? And roughly how long would this take? Months / years / decades / longer?

Yes - AdMech does that.
Longer
Not locked away in an STC - though undoubtedly locked away/lost are the secrets for highly efficient and quick way to modify environments and designing whole ecologies.

Answer 3

In the Forgebane Booklet it is mentioned how the Adeptus Mechanicus make use of air scrubbers and moisture generators to make a planet habitable before settling it to build the infrastructure.

And the Cadian Honour novel begins with the Imperium reintroducing life to a world left barren by the forces of Chaos.

So yes the Imperium still has the technology to do terraforming.