Weirdly, the process of plate tectonics would itself be in a bit of trouble. One tectonic plate subducts beneath another because it’s denser, but say you’ve got two plates that are composed of the same material – what then?
Well, they’d probably make like India and Eurasia – two equally dense continental plates – and ram into each other, forcing much of themselves upwards into the sky and forming the Himalayas.
It’s thought that, in a case where two tectonic plates are roughly the same density, one only efficiently sinks beneath the other thanks to the weight of the sediment-filled ocean sitting on top of it.
Without an ocean present, one of the plates won’t be weighed down by any accumulating sediment. It won’t be pushed beneath the other and subducted. Instead, the two plates will keep running into each other.
So, if aliens sucked away all the oceans today, any oceanic plate running into another oceanic plate, or any continental plate coming up against a continental plate, would ultimately smash into each other and form a huge series of mountain ranges.
Essentially, then, if Earth did have all its non-biological water stolen, it would rapidly become a superheated desert world full of continent-sized chasms of death and, eventually, ridiculously high mountains.
Hey there little guy
Mexico's Cave of the Crystals, which contains examples of currently unidentified microbial life in states of suspended animation. Alexander Van Driessche/Wikimedia Commons; CC BY 3.0
Life, however, would find a way. Microscopic life, that is – the type that didn’t need to rely on water to survive.
It’s likely that life needed water at first to emerge – and almost all life today requires it – but as evolution ran its course, microbes known as “extremophiles” have appeared. Unbelievably hot environments, powerful acids, and a lack of sunlight or water actually appear to suit some of these absolutely minuscule lifeforms.
Some of these exist within the crust and thrive, using carbon monoxide to produce nutrients. As a NASA team recently discovered, others hide away in gigantic crystals existing in a state of suspended animation.
So yes, humanity would be doomed if all the water on Earth was stolen. Yes, the planet would be a gigantic desert wasteland with insane topography. Sneaking around in the shadows, though, will be the extremophiles, slowly taking over the world long after the hydrophilic aliens have left.
Maybe they could avenge us.