A paper she read in the journal Nature finally spurred her into action. Soil organic matter, which is necessary for growing plants, is itself made of decomposing plant and animal material. That would seem to preclude Martian agriculture from ever being achieved. But researchers had demonstrated for the first time that you can actually form soil organic matter with microorganisms alone—no decaying plants needed. The microbes themselves, and their tissues and excretions, could synthesize soil.
Delgado realized that perchlorates could be the initial catalyst, the thing that microbes could thrive on and break down. Eventually the process could make the Martian regolith ready for planting.
She applied for an Emerging Frontiers in Research and Innovation grant from the National Science Foundation to explore the idea. NASA recognized her proposal’s implications and co-funded the grant; the project received $1.9 million total in 2022. It was intended as a multiyear, multi-institution effort, with Delgado as principal investigator. The plan was that ASU, the lead institution, would explore using microbes to lower the concentration of perchlorates in Mars-like dirt. The University of Arizona in Tucson would investigate the soil organic matter formed by those microbes during their breakdown of the perchlorates, and the Florida Institute of Technology in Melbourne, Florida, would figure out how to grow the plants.
Testing the dirt
One problem with studying Martian regolith is that we simply don’t have any of it here on Earth. NASA’s entire campaign of Mars exploration for 50 years has been in service of characterizing the Red Planet as a possible site for life. The agency has long sought to get a pristine sample of regolith from Mars into a clean room on Earth for analysis. But so far it has failed to develop a credible mission to do so. In April, Bill Nelson, the administrator of NASA, essentially admitted defeat, asking outside research institutions and the private sector for proposals on how an affordable Mars sample return might be achieved.
In the meantime, scientists have to make do with simulated Martian dirt to study ways to diminish levels of perchlorates, including heat, radiation, and microbial methods.
Delgado’s lab at ASU includes an incubator and a confocal microscope inside a custom-built anaerobic chamber, for analyzing microorganisms that are sensitive to oxygen. At a research station lined with sealed glassware of various sizes, plus syringes, pipettes, and other equipment, she introduces me to two of her doctoral students: Alba Medina, who is studying environmental engineering, and Briana Paiz, who studies biological design. Both are lead researchers on the project.
In sealed bottles on the table are solutions of various colors ranging from tan to black. In the more transparent solutions, a red material sits at the bottom that looks suspiciously similar in color to the dirt on Mars. “These are called microcosm bottles,” Delgado says. “To maintain the integrity of the chemicals and composition, anything that needs to be put in or taken out of the bottles has to be done by syringe and needle.”
The bottles contain nutrients, water (a requirement for life), and artificial Mars dirt. With no Martian regolith available, Delgado uses an “analogue” called MGS-1—Mars Global Simulant—with chemical and mineral composition, proportions, and physical properties engineered to match up with the specs measured by the Mars rover Curiosity. The simulant is made by a company called Space Resource Technologies and is publicly available. You can buy it online.