The thermodynamics of ancient clays on Mars seems inconsistent with the idea that a thick atmosphere of carbon dioxide caused a warm, wet era in the planet's early history. What did cause it remains an enigma.

The inability to efficiently deliver small interfering RNAs to target organs hinders their therapeutic application. So a demonstration of siRNA delivery to a notoriously difficult organ — the brain — is very exciting indeed.

T cells of the immune system recognize lipids, as well as peptides, extending our ideas about such target antigens. A crystal structure of a T-cell receptor docked to antigen shows how a sugar controls lipid recognition.