The idea that arid western landscapes resemble distant planets is not new. Hollywood recognized this years ago and frequently used public lands to film science fiction movies set on distant planets. In addition, the Mars Society located the Mars Desert Research Station in Hanksville, Utah, because of the area’s similarity to Mars in both climate and geography.
Chan notes that while geologists cannot study the sedimentary environment on Mars in person, they can look to the wind and water patterns in similar environments on Earth to help explain some of the patterns satellite or rover images reveal of the distant planet. One of the places on Earth most suitable for this study is the Colorado Plateau. “Its lack of vegetative cover reveals spectacular exposures which are surprisingly accessible for study,” says Chan. “Satellite images of these areas can then be compared to images of Mars. For example,” she explains, “sand dune patterns seen in satellite images of the surface of Mars point to the processes of wind shaping the landscape.” This is what Chan calls terrestrial analogs - using earth examples to interpret imagery from Mars.
One of the driving forces behind the study of Mars is the search for evidence of life. On Earth, life is associated with water, and so scientists look for evidence of water on Mars. Chan asserts that the desert of southern Utah is a good place to study that as well.
She points to the Jurassic Navajo Sandstone of southern Utah, one of the famous red rock formations. The different hues of red and white colors reflect the history of iron cycling and fluid flow; it is porous material. Of all the major layers on the Colorado Plateau, the Navajo Sandstone is the one that is most like a sponge, that has the greatest porosity.
It is also the place where one is most likely to find numerous round concentrations of mineral masses -- called hematite concretions, or sometimes called marbles. Geologists believe these formed underground perhaps some 25 million years ago, when flowing groundwater leached iron that cemented some of the sandstone into these hard, erosion-resistant balls. Because the surrounding sandstone eroded away over millions of years, many of these hematite concretions are exposed in certain areas of the Colorado Plateau, including Grand Staircase-Escalante National Monument.
Chan’s work focuses on these concretions. “They have certain characteristics that tell us they are formed by flowing groundwater, seeping through rocks the way water soaks through a sponge – precipitating minerals. Hematite formation is associated with water. And based on our study of hematite and other iron oxides in southern Utah, we suspected there might be similar hematite concretions on Mars.”
This was confirmed in 2004 when the NASA Mars Rover Opportunity sent back images of similar-looking “blueberry” spheres; their shapes and the way they were positioned in the rock led Chan to suggest that, based on terrestrial analogs from the Grand Staircase environment, they may have been formed in a similar way, leading to evidence of groundwater flow on Mars.
“Some marbles are round, some are stretched out,” she says. “These clues tell us how fluid moves through the rock. When we study these shapes on Earth, we can determine how they got that way. When we see them on Mars, we suspect there is a similar process at work. So even though the exact geochemistry and mineralogy may differ, the Navajo examples in southern Utah are extremely useful in interpreting the evidence of geologic processes that we see in the satellite imagery and rover reports of Mars.”
Chan believes this is only the beginning. “There are many more scientific explorations, comparisons, and sites for study of terrestrial analogs in BLM’s spectacular National Landscape Conservation System.”
“The study of sedimentary rocks on the public lands of the Colorado Plateau offers a valuable training ground for planetary scientists.” Dr. Marjorie Chan, Professor of geology and geophysics, University of Utah.