Habitable Worlds Quotes

Stars, of course, are too hot to support life, so wherever life might exist in the universe, it has to be on planets or moons that are warmed, but not incinerated, by the stars they travel around.

For many centuries, humans have speculated that there might be planetary systems around other stars and that there could be extraterrestrial life there and even intelligent being. However, those were simply speculations, and now we have evidence for the first part of these ideas.

NASA, and all the other spacefaring nations of the world, have agreed to a set of 'planetary-protection' principles, aimed at preventing the accidental contamination of another habitable world with organisms from Earth.

The story seems to be that almost every star has a planetary system... and, also, the definition of 'habitable zone' has expanded. In our system, it used to be that only Mars and Earth were potentially habitable. Now we've got an ocean on Europa... Titan.

Ultimately, what we're looking for in the long run is to find other Earth-like planets.

Prebiotic chemistry on other worlds is going to be common. Plenty of small rocky planets will have similar chemistry. It's almost a given.

Estimates are that at least 70 per cent of all stars are accompanied by planets, and since the latter can occur in systems rather than as individuals (think of our own solar system), the number of planets in the Milky Way galaxy is of order one trillion.

I am not sufficiently conceited to think that my sun is the only one with a family of planets and, therefore, that our little earth is unique. Once we admit that the other stars probably also have planets, at any rate a goodly proportion of them, it is more than likely that a large fraction of these will be the right size to keep on their surface water and, possibly, an atmosphere of some sort; and, furthermore, at the proper distance from their parent sun, to maintain a suitable temperature.

Naturally, we think that finding another Earth-like planet is identifying a site that's at least friendly here for the evolution of life. The primary goal of the Kepler mission is to statistically assess the occurrence of these small terrestrial worlds.

Planets that don't currently sport plate tectonics, such as Venus and Mars, are scarcely habitable. Tectonics might be a requirement of any world that aspires to a rich diversity of life.

Because of Hubble and other telescopes, we've now discovered that there are probably planets around every star, or virtually every star. There are solar systems around most stars. And the fact that we're here on a planet, Earth, means that it's likely there's lots of other Earths out there.

The number of habitable worlds in our galaxy is certainly in the tens of billions, minimum, and we haven't even talked about the moons. And the number of galaxies we can see, other than our own, is about 100 billion.