Much can be learned about the planets of the Solar System using geoscience knowledge, methods and reasoning. Similarly, investigations of known geophysical phenomena in a different setting — for example, rainfall in the hydrocarbon atmosphere of Saturn's moon Titan — can bring fresh insights for Earth.

To foster such a cross-fertilization of ideas, we at Nature Geoscience have welcomed papers from the planetary sciences since the journal launch. With the ongoing and rapid expansion of information on extrasolar planets, in terms of both the number of known exoplanets and their characterization, we are pleased to extend the invitation to scientists studying planets outside the Solar System, as long as the reasoning is rooted in the geosciences.

A true exploratory buzz of excitement is accompanying the discovery of more — and stranger — planets outside the Solar System. The flurry of search activities started a few years ago in the field of astronomy, which provides the tools for the identification of exoplanets. At the January 2013 meeting of the American Astronomical Society in Long Beach, California, extrasolar planets featured on most days of the programme. But Earth and planetary scientists have been quick to take the bait. For example, a Chapman conference (American Geophysical Union) in June 2013 will be dedicated to discussing the atmosphere of the Earth, the Solar System planets and exoplanets (http://chapman.agu.org/planetaryatmospheres/).

Most exciting, from an Earth and planetary science perspective, is that astronomers are not only discovering planets that circle other stars, but are beginning to also glean sufficient information about their size, mass and orbit to allow geophysical analyses into composition, climate and circulation. A Commentary on page 81 portrays a number of candidate planets and planet–star configurations that could lend themselves to geoscientific study.

The most eagerly pursued question in exoplanet research is that of habitability. Humans will always want to know if there is life out there in the Universe (and if so, where and in what circumstances). Answering questions may take a while. In the mean time, the sheer number and variety of exoplanets will allow us to test our ideas about the laws of geophysics in unimagined ways. At Nature Geoscience, we look forward to reading about that journey of discovery.