In “Life’s secrets lie in stars and Petri dishes” (New Scientist, 25 January 2012), Marcus Chown tells us about astrophysicist Dimitar Sasselov’s new “inspirational” book, The Life of Super-Earths: How the Hunt for Alien Worlds and Artificial Cells Will Revolutionize Life on Our Planet :
Of crucial importance to the life question, which explains Sasselov’s title, is a certain type of extrasolar planet, a super-Earth. These are solid planets of rock and ice between 1 and 10 times the mass of the Earth. We never suspected they existed because, in our own solar system, with its rocky terrestrial planets and bloated gas giants, such bodies are conspicuous by their absence.
It is these super-Earths that are key, argues Sasselov. They are even more attractive as life-bearing worlds than our home planet. They have a relatively small surface area to volume ratio, for instance, so they are better at holding on to their internal heat than Earth. That makes them likely to have the plate tectonics necessary to prevent carbon dioxide from volcanoes building up to dangerous, Venusian levels. If born with sufficient ice, super-Earths may even have giant oceans spanning the surface, 10 times deeper than any ocean on Earth. Think of those as habitats.
Sasselov argues that their temperatures might favour the survival of large molecules and the maintenance of temperatures needed for the origin of life.
Overall, we are given to understand here that Earth limits our imaginations, regarding life. Perhaps, but limits give shape to thoughts. When people get to the point of thinking, for example, that cancer cells are new species, it is time to put the lid on. We may encounter similar judgment calls re enthusiasm about finds on super Earths.