From Earth to Mars There are two schools of thought as it concerns the early Martian surface. The first is that, about 3.5 billion of years ago, Mars used to be a cold and icy planet. The second contends that Mars had a more temperate climate, and rivers and lakes flowed over the land. So, which theory is correct? The answer lies in an unlikely place: The bottom of a California lake. That is where UWM graduate student Gayantha R. L. Kodikara (“Kodi”), who is working toward his PhD in geosciences, is examining lake sediments in hopes of better understanding a class of minerals called zeolites. In turn, those zeolites on Earth might give researchers a better understanding of Mars. Answers in zeolite Zeolites are a class of minerals that form within a wide variety of rock types, both in marine and nonmarine environments – especially in areas where volcanic ash reacts with different sources of water. Scientists mainly find them in saline-alkaline lakes, in deep sea sediments, hydrothermal environments, and in certain soils and land surfaces on Earth. The general rule is that zeolites need some form of water in order to form their structure from precursor materials. Therefore, Kodikara said, if scientists can infer that zeolites form on Earth in certain circumstances – a closed basin lake where volcaniclastic materials are present, for example – then it’s reasonable to deduce that zeolites will form, or did form, under the same circumstances on Mars. “When we look at Mars, we have a lot of signatures of volcanoes. There are key minerals that indicate a hydrothermal process,” Kodikara pointed out. “Then we
6 • IN FOCUS • May, 2021
Geosciences PhD student Gayantha Kodikara sits in on the shore of Lake Tecopa in California in 2019, gathering samples of zeolites. Photo courtesy of Gayantha Kodikara.
have rivers, that carved canyons on Mars. Then we have lakes, closed basin lakes with inlets and open basin lakes with inlets and outlets, and seas.” In other words, there are plenty of places on the Martian surface where it’s likely that zeolites may have formed. So, where are they? “We have data mainly from four rovers on Mars: Spirit, Opportunity, Curiosity, and Perseverance. These rovers studied several locations on Mars, but none of them have found these zeolite minerals yet,” Kodikara said. “We have a lot of images from Mars covered by satellites, but from these satellite images only one (zeolite) mineral called analcime have been identified as a possible detection.”
