Falling space debris should make craters on rocky surfaces. (newscientist.com)
A sample of dozens of exoEarths opens up the opportunity to identify truly Earth - like worlds with rocky surfaces and oceans, amidst a complex zoo of other varieties of terrestrial planets. (hdstvision.org)
Few reliable clues exist as to the early history of Earth's atmosphere and rocky surface because geologic activity has erased detailed evidence over time. (scientificamerican.com)