I liked reading the section of the book that talked about how we know that there was water on Mars. I’ve always heard this fact about Mars being livable because it has water, but didn’t think about how they figured that out. I learned that there are actually no bodies on water on Mars today because the surface conditions would not allow that. Any bodies of water would turn into ice because of Mars’ temperature or into gaseous form because of the low air pressure. However, there is evidence of water erosion which shows that Mars must have used to have a much warmer climate and higher atmospheric pressure. They believe that water has not been on Mars for about 3 billion years.
When the rovers “Spirit”, “Opportunity”, and “Curiosity” landed on Mars, they captured lots of photo evidence that proved the existence of water on Mars at one point in time. “Opportunity” found tiny spheres composed of the minerals hematite and jarosite, which both form in salty, acidic water. “Curiosity” found that the dried clay and sedimentary rocks at the lower elevations on Mars show that there was pure water there. The chemical analysis of the rocks showed that they are made up of minerals that form in pure water, like lakes on Earth. Based on the data from these rovers, scientists were able to conclude that there was a vast lake at Gale Crater and it dried out 3 billion years ago. The older layers of rock were formed when the water was quite pure, and the newer and higher layers of rock formed as the water became more acidic and began to dry up.
I enjoyed learning about this topic and it made me wonder if Mars will ever evolve back into a warmer climate with higher atmospheric pressure and be able to have flowing water again, especially in case we ever need to move to Mars.