Microbes can travel vast distances by hitching a ride on dust particles propelled by strong winds. This intriguing finding, shared by Armando Azua-Bustos et al. in Scientific Reports last week, aligns perfectly with my interests. Naturally, I reached out to Armando for a discussion about this discovery.

Dr. Armando Azua-Bustos is an astrobiologist at Spain’s Center of Astrobiology in Madrid. His research focuses on the evolution of life on Earth, particularly how microbes adapt to extreme environments. He applies these insights to formulate evidence-based theories regarding the potential evolution of life on other planets, including Mars, and to develop methods for detecting signs of life beyond Earth.

The Atacama Desert in Chile serves as a terrestrial analog for Mars. Some regions within the Atacama boast a humidity level of 0%, making it the driest place on Earth, even drier than Mars itself. Despite this harshness, life persists; for example, bacteria flourish in the soil of María Elena South, the driest area in the desert.

Azua-Bustos’s background is captivating. He hails from a small mining town in the Atacama Desert, where his family was attracted by the benefits offered to miners, such as housing and healthcare. When these incentives were withdrawn due to financial issues, many miners left, prompting his family to relocate closer to the Andes for his father's job at a copper mine.

Although he moved from the most arid core, Azua-Bustos spent countless weekends as a teenager exploring the desert with his telescope, searching for fossils, Inca paths, insects, and flora. This formative experience greatly benefited his later research, as he developed an intimate understanding of the desert's geography. In a TED talk, he describes how he was able to identify the driest part of the Atacama Desert even better than NASA.

When I asked if his scientific curiosity was common among his peers in high school, he replied negatively. “I was the only one passionate about science during my teenage years. I can’t recall anyone else who shared that interest, except for a friend whose father enjoyed science. That was about it.”

This challenges my assumption that the breathtaking Atacama Desert would naturally encourage scientific inquiry. I had projected my fascination onto the local populace, imagining the wonder of growing up under a sky filled with stars. To me, this is a captivating novelty. However, I realize that the expansive, clear view of the cosmos might become ordinary to those living in such an environment. Azua-Bustos seems to be one of the rare individuals who maintain a sense of wonder in his own backyard.

“I recall walking in the Atacama on a moonless night and seeing my shadow cast by the starlight—a 'star shadow.' It's remarkable, and I doubt many places in the world offer such a sight,” said Azua-Bustos in an interview with Nerina Finetto for Traces.Dreams.

Edit to original, September 6th, 2019: After visiting San Pedro de Atacama, I believe my theory holds more truth. If I had to describe the people I encountered there in one word, it would be "curious." While they may not conduct experiments, they possess a strong desire to explore and comprehend their surroundings.

In 2015, Azua-Bustos identified María Elena South as the driest location in the Atacama Desert, discovering various bacterial species thriving in its soil (published in Environmental Microbiology Reports). The desert generally receives less than an inch of rain annually, with some areas, like María Elena South, receiving none at all. How does life persist in such conditions? And how did it arrive? The first question remains under investigation, but the wind might hold the answer to the second.

Wind-driven processes, known as Aeolian processes, significantly shape desert landscapes. In the Atacama Desert, located between the Chilean Coastal Range and the Andes, these mountains capture most incoming moisture, leaving the region in a rain shadow.

In their 2019 study, Azua-Bustos et al. utilized earth.nullschool.net and their own measurements to analyze wind patterns in the desert. Each afternoon, a strong wind blows eastward from the Pacific Ocean into the desert. Could this dust, laden with microbes, travel inland? To explore this, Azua-Bustos selected six sampling sites along two transects for collection plates. The northern transect extends 63 km from Iquique, while the southern transect reaches 50 km from Tocopilla.

They employed 50 petri dishes at each site, with 40 containing agar and growth medium, and 10 left empty. The lids were removed for just one hour, and while I inquired if they positioned the plates toward the wind, Azua-Bustos clarified they laid them flat to capture only settling dust. Afterward, the plates were sealed for analysis two weeks later.

Azua-Bustos initially expected no microbial growth on the plates; it was merely a test of a speculative idea. To his surprise, he isolated multiple bacterial and fungal species from every site. In the Iquique transect, he identified five bacterial and four fungal species, while the Tocopilla transect yielded 18 bacterial and four fungal species. The bacteria typically originated from nearby areas, with coastal plates collecting oceanic bacteria, and inland plates capturing those likely found in mountainous regions. Some of the microbes utilize spores for dispersion, suggesting that airborne spores may be carried inland by the wind, while others likely traveled on dust particles.

To confirm this, dust collected on sterile plates underwent DNA extraction and 16S ribosomal RNA sequencing, revealing an even greater diversity of bacterial species. Azua-Bustos is currently employing scanning electron microscopy to visualize microbes attached to dust, which I eagerly anticipate seeing.

“The analysis of dust particles collected across the hyperarid core of the Atacama shows that microbial life can efficiently traverse the driest and most UV-exposed desert on Earth unharmed. The primary factor driving the transport of microbial life in this desert is the speed and presence of winds.” — From Aeolian transport of viable microbial life across the Atacama Desert, Chile: Implications for Mars (Scientific Reports, 2019).

The pressing question now is: what happens to these microbes once they arrive in the hyper-arid desert? Can some adapt and thrive in this arid environment? The bacteria discovered by Azua-Bustos in 2015 must have originated somewhere. Aeolian transport may provide an explanation.

I suspect that most microbes that reach the desert perish. Occasionally, they might land in a micro-habitat shielded from environmental stressors, allowing the most resilient to survive and reproduce. However, this is merely conjecture and remains an active area of research for Azua-Bustos and his team.

The realization that wind can transport microbes has profound implications for the potential for life on Mars, where dust storms can envelop the entire planet. It raises the possibility that wind may have similarly facilitated the dispersal of early microbial life on Mars, allowing them to spread widely before settling into diverse ecological niches.

“As previously suggested, the absence of consistently hospitable conditions on Mars may have hindered continuous biological evolution. Our findings provide a framework to address this issue, as the lack of connectivity between dispersed habitable environments due to ancient water flow or tectonics might have been offset by wind dispersal of microorganisms over extended periods. Consequently, the aeolian distribution of life could have enabled some degree of evolution among Martian microbial life forms.” — From Aeolian transport of viable microbial life across the Atacama Desert, Chile: Implications for Mars (Scientific Reports, 2019).

Our discussion then shifted toward speculation. Could our space missions and human explorations be unintentionally introducing Earth microbes to other planets? How do humans adapt to life in the desert? Might bacteria and humans form symbiotic relationships to survive in arid climates? I’ll keep these questions in mind for future science fiction writing, but they certainly warrant scientific investigation.

In closing, I informed Armando about my upcoming trip to the Atacama Desert and asked for any advice. I was hoping for insider tips on places to visit or people to meet, but his response was straightforward: drink plenty of water and apply sunscreen liberally. Sound advice, considering I’m akin to a coastal microbe blown in by the wind.