In the Footsteps of Mars: Exploring Mars-like Environments in Spain

What do southern Spain and Mars have in common? More than you might think. I'm Manuel Gruber, a master's student at the Institute for Astrophysics. In February 2025, as part of a research expedition organized by the University of Vienna and led by Professor David Carlos Fernández Remolar, we traveled to Córdoba and Rio Tinto to investigate extreme habitats on Earth. We were supported by Dr. Angélica Anglés and her husband, Hamilton Muirhead, from ESA Madrid. The goal was to explore possible analogies to Mars and to better understand the conditions under which life could exist beyond Earth.

At the beginning, we studied geological material and the formation of the mountains in this region. The main goal of the excursion was to find a specific mineral that has already been discovered on Mars and to compare it with Mars-like meteorite material found on Earth. 

Our exploration began in Córdoba. We spent a few days there, and Professor Remolar first gave us an overview of the historical background and fundamental knowledge about geological material. During our stay in Córdoba, we learned primarily how the mountain landscapes were formed and that these regions were underwater millions of years ago. This was also the reason why we found small, sponge-like fossils high in the mountains and not near the city. These fossils are approximately 500 million years old, making them even older than the dinosaurs! After these exciting initial discoveries, the excursion became increasingly interesting. 

Afterwards, we traveled to Rio Tinto, where we stayed in accommodations that had been used by NASA a few years earlier. We generally visited research areas where NASA had conducted studies. In the following days, we drove to various locations around Rio Tinto in search of a mineral called "jarosite." But what makes jarosite so interesting, and why look for it in that particular place? 

Jarosite is a common secondary iron-potassium sulfate mineral. It is known for its pale yellow to brownish color and typically forms through the weathering of pyrite in acidic environments. Because its formation is linked to water and acidic conditions, jarosite—especially after its discovery on Mars—plays an important role in astrobiology. Rio Tinto was chosen for this study because it has a particularly extreme environment. The approximately 100-km-long river in Andalusia is known for its striking red color and high acidity (pH ~2). These conditions resulted from millennia of copper and pyrite mining in the Sierra Morena. Due to its exceptional properties, Rio Tinto is often referred to as "Mars on Earth." As mentioned earlier, NASA and ESA use this region to search for evidence of possible extraterrestrial life—just as we did during our excursion.

The most fascinating aspect for me as a student wasn't just participating in this extraordinary field trip, but also the opportunity to work in the same locations and conduct similar investigations to those NASA had done a few years earlier. We were able to observe impressive things, including a blood-red river and even red-colored bodies of water, and we also found interesting geological materials. Dr. Angélica Anglés took numerous samples of the red water and the collected material for later analysis in the laboratory. The goal was to determine whether it was indeed jarosite. The mineral wasn't easy to find, but it could be of great importance to her ongoing research at ESA Madrid on the topic of life on other planets. 

Overall, it was a very exciting and impressive research excursion, during which I learned a great deal about geological materials, astrobiology, and current research on the origin and possible existence of life on other planets. I would recommend that every student take advantage of such an opportunity if it arises. It's an unforgettable experience.

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