- Mars reached half its present size in just 1.8 million years or less, a new study shows.
- Unlike Earth, Mars didn't feed off other planetoids, which kept it small and relatively intact.
Astronomers don't know how it happened, but Mars appears to have sat out the game of planetary billiards that marked the solar system's early days, surviving as a quickly formed, diminutive and relatively unaltered embryo planet, a new study shows.
The finding offers an explanation to the long-standing mystery of why Mars, the fourth planet from the sun, is so small, lead researcher Nicolas Dauphas, with the University of Chicago, tells Discovery News.
"There was this problem of explaining the small size of Mars," Dauphas said. "There were ideas floating around in the scientific community, but the question was what do you measure to tell whether these ideas are a fairy tale or whether it corresponds to what happened."
Dauphas and colleagues decided to attack the problem by figuring out how fast it took Mars to form, a study that entailed painstaking analysis of radioactive materials in 20 Mars meteorites and comparative studies of 30 chondrite meteorites, which are believed to be leftover remains from the solar system's earliest days.