Water Everywhere on Early Mars But Only for a Geologic Moment?

摘要

The early Mars of human imagination has swung from invitingly moist to brutally dry and back again more than once in the past half-century. Hopes for some sign of life that might have struggled into existence in that first billion years of martian history have likewise been alternately buoyed and dashed. In recent years, much of the news has been decidedly wet: a shallow, salty sea, rivers languidly flowing into crater lakes, and an exploding palette of spectral colors denoting water-altered minerals. Most of these sorts of once-wet martian features are in the running to be the lone landing site for the next U.S. Mars rover, the $1.9 billion Mars Science Laboratory (MSL). Its mission: "follow the water" to understand whether the planet has ever been able to support microbial life.