Support WBURSigns Of Life On Mars? Not ExactlyPlay02:59Download AudioJoe PalcaDecember 02, 2012 ShareNASA's Mars rover Curiosity cut a wheel scuff mark into a wind-formed ripple at the "Rocknest" site to give researchers a better opportunity to examine the particle-size distribution of the material forming the ripple. (NASA/JPL-Caltech)