<span>Geologists searching for clues to the ancestors of modern-day vertebrate land animals should look in layer 2 , of the fossil beds.
As the fossils get older, the fossils will be buried deeper within the layer of the fossil beds. Within layer 2 of the fossil beds, Geologist could found the fossils that came from ancient sera Valli an age</span>
By their activity in the soul
The planetary body that Spirit was designed to explore the wide ranges of soil and rocks for clues of the water activity on Mars. Spirit specifically landed at the Gusev Crater which was before, a possible lake in a giant crater.
An example of secondary pollutant is sulfurage
