New calculations suggest that Mars's frozen subsurface could contain networks of narrow liquid water channels large enough to support microbial life. These veins, formed in permafrost, might exist in regions with high salt content that prevents freezing. Researchers argue this could be a promising site for searching extraterrestrial life.
A study published in Icarus reveals that the Martian permafrost may harbor tiny veins of liquid water, potentially creating habitable environments for microscopic organisms. Hanna Sizemore at the Planetary Science Institute in Arizona led the research, initially aiming to disprove the possibility but ultimately finding evidence to the contrary.
"For Mars we always live on the edge of maybe habitable, maybe not, so I set out to do this research thinking maybe I can close this loop and say that it’s very unlikely to have enough water and have it be arranged so that it’s habitable for microbes," Sizemore said. "I proved myself wrong."
Using soil composition data from NASA's Phoenix spacecraft, which landed on Mars in 2008, the team calculated the potential for liquid water in icy soils. Mars's surface temperatures can drop to -150°C (-240°F), but abundant salts lower water's freezing point below 0°C, allowing liquid to persist in narrow channels. The researchers determined it is "surprisingly easy" to form soil with more than 5 percent liquid water flowing through channels at least 5 microns in diameter—sufficient for habitability.
"The largest veins we’re talking about are 10 times narrower than very fine human hair," Sizemore explained. "But it’s a large enough environment to submerge a microbe, and [they are] connected enough to move food and waste through the environment."
These networks could be abundant at latitudes higher than 50 degrees. If life exists on Mars, Sizemore suggests these veins are the easiest target: "This is an environment where we can land and dig down like 30 centimetres and sample this."
However, the cold temperatures pose challenges, as they exceed limits for most Earth-based life. Bruce Jakosky at the University of Colorado Boulder cautioned, "We have to be careful, though, about using the limits in which terrestrial life can grow and metabolise, as they do not necessarily represent the limits in which any life, anywhere, could function." He added, "The bottom line is that... it’s not impossible that life could exist in the Martian near surface."