The operative word: "SPECULATES"
Speculation by "19 physicists, astronomers, and climatologists" who are expressing opinions about their fields of expertise is worthy of consideration. But if you feel otherwise, that's up to you.
Both the words speculate and possible are being misused. If we are to reason in the Platonic way we need to retreat to a prescientific stage. Plato was not familiar with the scientific method and did not have access to measurements showing the presence of water on these celestial bodies and would not have demonstrated any possibility at all of life on these celestial bodies. Now we have measurement of water on these celestial bodies and water has the possibility of life.
People also speculated that the Earth was Round..