A fluid phase must be present on the planet in question, for material must cycle to the organism as food and away from the organism as waste.
These organisms may be considered as analogues to the possible biologically pigmented surfaces that may be present on other planets.
It is located at the edge of the habitable zone - the narrow strip around a star where liquid water can be present on the surface of a planet.
They also announced that three of the seven planets are thought to lie within the so-called Goldilocks zone, where temperatures are warm enough - but not too warm - for liquid water to be present on surface, making the planets potentially habitable.
De Pater's group suggested that a similar phenomenon would be present on Neptune, based upon Keck observations of that planet.
These findings will allow us to look for areas where water might have been present on the planet and where life might have been a possibility.
What we do know is that it is within the so-called "habitable zone", meaning that if water is present on the planet, it could be in liquid form.
Demand for energy by our increasing population over the past half-century has led to an accumulation of atmospheric carbon dioxide, the concentration of which – now 400 parts per million – has not been present on this planet for several million years.
Kepler-11f's low density, characteristic of the outer planets of the system, suggests that a large hydrogen helium atmosphere is present on these planets, classifying it as "gas dwarf" due to its small size and mass.
Nasa announced on Thursday that three scientific lines of enquiry have led them to conclude that water ice and organic molecules are present on Mercury, the closest planet to the sun, and the smallest planet in the solar system.
At one extreme (left panel) there is only one possible sequence of events that could result in our planet developing a biosphere, implying that life could not emerge unless very specific conditions were present on Earth throughout its history.
