While I don't disagree that estimates could be made, OP's image looks like that of a white shrimp, which is a life form on Earth. What about the image is "alien"? This thing evolved to live on Earth. It looks like something that evolved to live on Earth in a dark area.

There's a short series from the mid-2000s that I remember watching about an imaginative expedition to a close planet and the life on it. https://www.imdb.com/title/tt0453446/