A thing a lot of people don't seem to be aware of is that the proportion of astronomers who believe there is alien life of some sort in the universe is almost 100%. It's just the proportion who think they've *dropped by* that's almost 0.

I had a radio interview recently where the host started out all challenging saying "It's UNTHINKABLE there isn't other life out there in the cosmos!" and I was like, "yeah, pretty much" and I think he was not really prepared for that

What we know is that we find life in just about every environment we look for it on Earth, wherever there's some amount of liquid water -- sometimes even just ice. And we know there is water on other worlds. And there are a LOT of other worlds. So: life seems likely to be common!

The reason Mars is so exciting to astrobiologists is that we have VERY good evidence that Mars a few billion years ago had conditions EXTREMELY similar to Earth. Liquid water on the surface, substantial atmosphere. If life arises everywhere it can, we should see signs of it there