Joel Achenbach writes about the search for life off earth and the recent measurement by the Curiosity Mars rover (see earlier post) that found no significant level of methane in the atmosphere : On Mars, no proof yet, but scientists’ search for extraterrestrial life continues – The Washington Post.

The lack of methane does not mean there cannot be subterranean life on Mars. Just that it is not the sort of bacteria that generates methane. The previous indications of methane were exciting because it would have been a fairly strong signal for life: Mars Science Laboratory | Mars rover gives negative result on Mars methane – Spaceflight Now.