Presently, astronomers only have a short period of observations to forecast the comet's path through the inner solar system and they know the probability of Mars "taking one for the celestial team" on Oct. 19, 2014, is small — in all likelihood the comet will fly by, creating a wonderful astronomical event for Earth and Mars-based observers alike.
This does NOT mean that anything ever actually lived there. But it is the first time that the ingredients for the evolution of microbial life, and the correct conditions to support it, have been directly observed beyond Earth. Mars still has water frozen at its poles, and once had quite a bit of water above and below the surface.
The tool is a motorized, wire-bristle brush designed to prepare selected rock surfaces for enhanced inspection by the rover's science instruments. It is built into the turret at the end of the rover's arm. In particular, the Alpha Particle X-ray Spectrometer and the Mars Hand Lens Imager, which share the turret with the brush and the rover's hammering drill, can gain information after dust removal that would not be accessible from a dust-blanketed rock.