A volcanic planet
The outer layer of Mars is a thick crust of volcanic rock. In the heavily cratered southern highlands and northern basaltic lowlands, volcanic activity stopped over three billion years ago. But two areas near the Martian equator, the Tharsis and Elyssium regions, were active until much more recently. In Tharsis, huge volcanoes, bigger than any on Earth, spewed out lava that piled up into a layer of basaltic rock about 120 kilometers (75 miles) deep.
Most Martian meteorites probably come from this highly volcanic region of Mars. Shergotty is a piece of lava that flowed onto the Martian surface as recently as 180 million years ago. The Governador Valadares meteorite is lava that was trapped underground and slowly crystallized about 1.3 billion years ago. This lava never reached the Martian surface—until it was excavated by the impact of a comet or asteroid.
Fell August 25, 1865
Gaya, Bihar, India
Keywords: Astrophysics, Basalt, Mars (Planet)--Geology, Mars (Planet)--Surface, Meteorites, Volcanoes, Volcanology