A few million years after the solar system was born, a young Jupiter may have journeyed inward, with an early Saturn following (chart shows masses and distances of outer planets from the sun over time). This trip could explain Mars’ small size (top right, in comparison with Earth); as Jupiter moved, it swept away much of the material that would have otherwise come together to form Mars.
Source: (graph): K.J. Walsh et al/Nature 2011 Credit: (Earth and Mars): Walter Myers/Photo Researchers, Inc.
Eruption early in human prehistory may have been more whimper than bang
Greed may breed financial fitness, but evolution allows unselfishness to survive
Fine-tuning of technique used in other animals could enable personalized medicine
Simulation suggests long-term effect on sea level not as dire as some predictions
Coverage of the 2013 American Association for the Advancement of Science meeting
The Year in Science 2012
Three-part series on the scientific struggle to explain the conscious self
Tables of contents, columns and FAQs on SN Prime for iPad