期刊介绍：

The vertebrate multiaminoacyl tRNA synthetase complex (MARS) is an assemblage of nine aminoacyl tRNA synthetases (ARSs) and three scaffold proteins. The evolutionary origin of MARS is unclear; in this issue, Fox and Eswarappa propose that there is an evolutionary and metabolic link between the coincident emergence of MARS and the citric acid cycle. On the cover, we show an artist’s rendering of what the planet Mars may have looked like at some point during its origin. Photo courtesy of iStockphoto/dvarg.