Don't talk to aliens

I'm spending a few months at Cambridge. I couldn't miss it therefore but be informed of the latest announcement of Professor Stephen Hawking, namely:

“To my mathematical brain, the numbers alone make thinking about aliens perfectly rational. The real challenge is to work out what aliens might actually be like.”

“We only have to look at ourselves to see how intelligent life might develop into something we wouldn’t want to meet. I imagine they might exist in massive ships, having used up all the resources from their home planet. Such advanced aliens would perhaps become nomads, looking to conquer and colonise whatever planets they can reach.”

“If aliens ever visit us, I think the outcome would be much as when Christopher Columbus first landed in America, which didn’t turn out very well for the Native Americans.”

However, today, another fact became known to me which, surely, and beyond any doubt, provides the definitive explanation about aliens:

The Gwizls, an alien species far more advanced than humans, missed their invasion of planet Earth and all disappeared in the depths of sea by lack of knowledge of the basic properties of water (H₂O)

The announcement was made by Professor Pierre Brémaud (visiting fellow of the Newton Institute for Mathematical Sciences). Proof below: