The second era
emerged after a dramatic shift in the Martian climate. Now sulphate
minerals dominated and this era has been labelled the 'Theiikian
Era', named after the Greek for sulphate. The
reserchers believe the change in mineral composition was caused
by volcanic activity around four billion years ago. With volcanic
eruption comes enormous releases of gas, amongst which there is
a lot of sulphur. The interaction between the sulphur and water
created sulphates. The
rovers 'Spirit' and 'Opportunity' both landed in sulphate-rich regions |