Rocks can tell us a lot about the environments in which they were formed. All of the following rocks have been discovered on Mars.

Sedimentary

Sedimentary rocks are formed by erosion and deposition. Most of the fossils on Earth are preserved in sedimentary rocks.  

Sandstone is made of grains of sand weathered and eroded from igneous rocks and deposited by water or wind. Sandstone is formed in beach or desert environments. 

Mudstone forms in deep still water such as at the bottom of oceans or lakes. 

Limestone is a carbonate; a type of mineral and rock that forms in the presence of water and most commonly forms in deep oceans or caves. 

Conglomerate rocks are formed in rivers and streams. The minerals, crystals and smaller stones inside them are rounded and polished by running water, which are cemented together by a matrix of sand and clay. 

Breccia is formed where rockslides occur, and the rocks and crystals within them are sharply angled and broken. 

Tuff is formed from volcanic ash released during an eruption. Photo of a Turkish landscape where tuff was deposited in the form of ash by nearby volcanos between 11 and 3 million years ago, which has since been eroded into fantastic shapes. The colour differences are due to variations in temperature and mineral composition of the lava from which the ash was derived during its eruption.

Basalt rocks are formed from lava that erupts on the surface and cools quickly. 

Granite forms from magma deep underground, where it cools and crystallises slowly over a very long time. 

TASK: Describe the environment in which the following rocks were formed, eg. beach, ocean, underground.  Give reasons for your answer. Which rocks are most likely to contain fossils?