For decades, scientists have been searching for signs of past life on Mars. While tantalizing hints have emerged – like evidence of ancient water lakes and organic molecules – concrete proof remains elusive. A new study, however, suggests that caves carved by flowing water beneath the Red Planet’s surface might hold crucial clues about whether life ever thrived there.
Mars is riddled with numerous depressions resembling cave entrances. Traditionally, these features were attributed to volcanic activity rather than watery erosion. On Earth, vast networks of caves known as karstic caves are formed when water dissolves soluble rock like limestone over millennia. Yet, despite ample evidence pointing to a wetter past on Mars billions of years ago, scientists have yet to pinpoint definitive examples of such water-carved caves.
Now, researchers led by Chunyu Ding at Shenzhen University in China believe they’ve identified eight potential candidates located in the Hebrus Valles region. This vast northwestern Martian area boasts hundreds of kilometers of valleys and depressions sculpted by ancient floods, suggesting a history of powerful water currents.
These cave entrances were initially mapped by missions like NASA’s Mars Global Surveyor. Ding and his team delved deeper using spectrometry data from that mission to analyze the chemical composition around the suspected caves. The results revealed a signature rich in carbonates and sulfates – minerals known to form in the presence of liquid water.
The team also unearthed evidence suggesting ancient streambeds that abruptly end near these cave entrances. This pattern closely mirrors what’s observed near karstic caves on Earth, where streams often disappear underground, diverted by subterranean cave systems.
“If you’re looking on a map, you would expect the stream to be on a surface, and then all of a sudden disappear, because the stream water is being pirated by the cave system,” explains James Baldini, an expert in Martian geology at Durham University in the UK.
While these findings paint a compelling picture, not everyone is convinced. Daniel Le Corre from the University of Kent acknowledges the mineralogical and geological evidence pointing towards potential water-carved caves but notes they visually resemble other Martian caves thought to be volcanic in origin.
If confirmed, these water caves would be prime locations for astrobiologists seeking evidence of ancient life. “In order to have life, you need water and an environment that is sheltered from the intense radioactive bombardment on the surface of Mars,” Baldini states. “Volcanic caves and lava tubes are also reasonable places to look for life, but there’s not necessarily any water involved.”
Furthermore, these Martian caves could potentially contain stalagmites – bulbous rock formations characteristic of karstic caves on Earth. Stalagmites act like geological time capsules, preserving information about past environmental conditions, including temperature changes over extended periods. However, determining the precise age of such stalagmites would be a formidable task, even with robotic exploration.
The search for life beyond Earth often hinges on finding environments where liquid water once flowed and sheltered life from harsh radiation. The possibility that these Martian caves might contain such remnants offers a tantalizing prospect for future exploration.
