How Does Life Take Hold in Barren Environments?

Explore

AAs the search for life on other planets continues, it raises questions about how communities of living organisms arise on sterile surfaces. Mars, for example, has expanses of bare basalt rock, testimony to its active volcanic past. Scientists wonder whether ancient volcanic eruptions on Mars could have promoted periods suitable for life, warming things up, melting ice and releasing gases.

In a study in Nature Communications BiologyEcologists and planetary scientists from the University of Arizona and the University of Iceland have found clues about how life resumed around an Icelandic volcano, which could provide clues about life elsewhere in the universe. The Fagradalsfjall volcano erupted three times between 2021 and 2023, providing an opportunity to study the consequences of multiple eruptions, each covering the tundra ecosystem around the volcano in lava.

“The lava coming out of the ground is over 2,000 degrees Fahrenheit, so it’s obviously completely sterile,” explained Nathan Hadland, first author and doctoral student at the University of Arizona’s Lunar and Planetary Laboratory, adding, “It’s a blank slate that essentially provides a natural laboratory for understanding how microbes colonize it.”

Read more: “The sound so loud it circled the Earth four times”

Microbes are the first colonists of bare surfaces. Hadland and the research team sampled microbes in DNA extracted from recently solidified lava, rainwater, and aerosol particles over the three-year study period. They found that the first microbes came primarily from airborne soils and particles blown onto fresh lava, such as Sphingomonas echinoidesa bacteria widespread in the soil.

These early settlers must be extremely resilient, because fresh lava is hot, dry, and low in available nutrients. Just cooled lava, for example, hosted Udaeobacter sp., a soil bacteria capable of surviving with virtually no nutrients. However, these early settlers did not survive well; Udaeobacter sp. abandoned during the first winter, then completely disappeared after a year.

In the 100 days following a Fagradalsfjall lava flow, microbes remained so rare that it is considered one of the lowest biomass environments on Earth, along with the driest part of the Atacama Desert, the study found. But after winter, other microbes arrived, mainly species carried by rainwater.

“Seeing this huge change after winter was pretty amazing,” said co-author Solange Duhamel, “and the fact that it was so repeatable and consistent across the three different eruptions – we didn’t expect that.”

By the third year, microbe assemblages became more stable, with less exchange between communities. Most of the species that managed to stand out were known from other volcanoes in Iceland and Hawaii. The results, modeled by the study authors, suggest that the colonization of a barren lava surface follows a predictable trajectory, which may apply to other volcanic systems, even those on Mars.

Enjoy Nautilus? Subscribe for free to our newsletter.

Main image: Ahsanjayacorp / Shutterstock

• Devin Reese

  Published on December 29, 2025

  Devin Reese is the editor-in-chief of Natural history and a science writer based in Alexandria, Virginia.