A small group of rare and unusual meteorites, consisting of three main subgroups: the shergottites, nakhlites, and chassignites (hence SNC). The SNC meteorites are igneous rocks that solidified from a cooling magma near the surface of their parent body, probably Mars. All but one are relatively young (less than 1.3 billion years old); the single ancient SNC meteorite found to date was formed about 4.5 billion years ago. The proportions and isotopic abundances of noble gases trapped in one shergottite resemble the composition of the Martian atmosphere as analysed by the Viking landers. SNC meteorites were probably ejected from Mars by impacts, and entered orbits around the Sun before falling to Earth.
Subjects: Astronomy and Astrophysics.