Salt-loving microbe grew and reproduced for 160 days under Mars-like conditions

A team led by Adam Robinson grew and reproduced cultures of the salt-loving archaeon Haloferax volcanii for 160 days under simulated Martian subsurface conditions, according to a study published Nov. 5, 2026 in Applied and Environmental Microbiology. The chamber held brine seven times saltier than seawater, an oxygen-free carbon dioxide atmosphere, pressure of about 24 millibars, and a temperature of 21 degrees Celsius, or about 70 degrees Fahrenheit.

Researchers supplied nitrate or perchlorate, chemicals found on Mars that can support respiration without oxygen. Cultures denied both chemicals stayed alive but showed no measurable growth, while every low-pressure treatment with one of the chemicals grew. Optical density, a measure of how densely the cells are growing, rose in each of those low-pressure cultures, though growth proceeded more slowly than in matching cultures at normal Earth pressure.

Nitrate fell by roughly 15 percent to 29 percent and perchlorate by roughly 16 percent to 29 percent in Mars-pressure cultures, while cell-free controls showed no declines. The team took measurements only at the beginning and end of the run because opening the chamber would have let oxygen in.

The pressure used in the experiment might exist within sealed fluid pockets in salt minerals roughly 20 centimeters beneath the Martian surface, the study authors said. That depth corresponds to about 24 millibars, or roughly 2 percent of Earth’s sea-level pressure.

Dense biofilm-like structures formed in actively growing low-pressure cultures but not in controls, and liquid loss across all treatments stayed below 4 percent over 160 days. The biofilms might have helped keep water in the salty solution, though the concentrated salt itself also reduced evaporation, leaving the biofilms’ precise contribution uncertain.

Earlier work tested Earth microbes under individual Martian stresses such as high salt or low pressure, or combined stresses for only hours or days, Robinson said. Far fewer studies combined these conditions and showed that microorganisms can actively grow, he added. “Far fewer have been able to combine these conditions together and show that microorganisms can actively grow”

The setup omitted Mars’s freeze-thaw cycles, radiation, and full chemistry, and the nutrient-rich growth medium did not represent the organics believed to exist on Mars. The researchers kept cultures at 21 degrees Celsius, far warmer than most of the Martian subsurface.

Robinson said the mimicked environment has not been observed on Mars but is theorized to exist. The findings may assist future missions in separating signs of ancient life from indicators of organisms that remain metabolically active and in evaluating the danger of Earth microbes contaminating Mars, according to the researchers. The authors stressed the result does not establish that life exists on Mars today.

Scott Perl said microbes that evolved within the Martian environment scientists consider hostile may find it hospitable. “They’ve evolved within the Martian environment that we consider hostile. So what is hostile to us isn’t necessarily going to be hostile to those microbes” Adam Robinson said the work adds to evidence suggesting researchers should consider the possibility of life on Mars today. “We are adding to the growing body of evidence suggesting that we should consider the possibility of life on Mars today”

No organisms from Mars have ever been found, so Scott Perl’s comments about microbes adapted to the Red Planet are hypothetical, according to the source. Perl said any life that arose on the planet would have had billions of years to adjust to changing conditions.

Haloferax volcanii is an archaeon, a group whose members resemble bacteria but form a separate branch of life and often thrive in scalding hot springs or salty lakes. The researchers chose it because salts on Mars could keep water underground liquid below its normal freezing point, and perchlorates detected on Mars can lower water’s freezing point. For decades, scientists have focused much of the search for Martian life on the distant past because ancient riverbeds and lake deposits suggest Mars was warmer and wetter billions of years ago.

Robinson and colleagues say the present-day Martian surface is generally inhospitable due to low atmospheric pressure, intense radiation, global desiccation, and oxidizing chemistry increased since the Late Noachian. Shallow subsurface regions with mineral evidence of groundwater movement might hold localized hypersaline settings able to keep liquid water and support microbial metabolism. Carotenoid pigment signatures, detectable by Raman spectroscopy and proposed as possible biosignatures (signs of life), remained detectable but weaker than in oxygen-fed controls.

The paper carries the DOI 10.1128/aem.01749-26 and appears in a journal published by the American Society for Microbiology. Adam Robinson led the study, co-led by Scott Perl of the Los Angeles Natural History Museum and the Blue Marble Space Institute of Science.