Planetary scientists have long wondered why Mars is only about half the size and one-tenth the mass of Earth. As next-door neighbors in the inner solar system, probably formed about the same time, why isn't Mars more like Earth and Venus in size and mass? A paper published in the journal Nature this week provides the first cohesive explanation and, by doing so, reveals an unexpected twist in the early lives of Jupiter and Saturn as well. Dr. Kevin Walsh, a research scientist at Southwest Research Institute® (SwRI®), led an international team performing simulations of the early solar system, demonstrating...