Rock analysis provides clues about Mars’s geologic history

Ars Technica : Satellite imagery of Mars suggests that the surface is mostly covered in basalt-like rock, but satellites can’t provide direct chemical analysis. That is why Curiosity, on the surface of Mars, has been using a laser to spectroscopically sample rocks it encounters. Violaine Sautter of the National Museum of Natural History in Paris and her colleagues have analyzed the data from 22 lighter-colored rocks the rover found, half of which were sampled with the laser. Several of the rocks were granite-like, with large crystals, and were similar to Earth’s earliest continental rocks. That finding suggests that at some point in its history, Mars too began forming continental plates. Instead of undergoing global-scale cooling, the planet possibly had regional variances in its rate of cooling. A higher presence of granite-like rocks could explain the difference in density that has been measured between Mars’s northern and southern hemispheres.