Free Astronomy Magazine March-April 2021

12 MARS ROVERS T his view of the rock “Chimp” was acquired by the Sojourner rover's right front camera on Sol 74. Below, the “Twin Peaks”, modest-size hills to the southwest of the Mars Pathfinder landing site. [NASA/JPL] rock’s mass – indicating very little water content. The APXS worked by irradiating rocks and soil samples with alpha particles (helium nuclei, i.e. two protons and two neutrons bound together). The results indi-