Earlier this month, NASA's Mars rover Curiosity came across an odd rock unlike any others found so far on the red planet. The rock was roughly egg-sized and shaped and appeared to have a dark gunmetal grey color. After Curiosity took a chemical sample using its autonomous “ChemCam” laser, it was determined that like Curiosity, the rock was not of Martian origin. NASA scientists concluded that the rock was likely a meteorite due to its composition of iron, nickel, phosphorous, and other metals. This meteorite and many like it are beginning to help astronomers piece together the story of water on Mars, and unfortunately for potential Mars colonists, the story is not an encouraging one.
According to a new study published in Nature Communications, data gathered from Martian meteorites indicate that the red planet has likely been devoid of liquid water for millions of years. This conclusion was drawn from the amounts of oxidation, or rust, found on iron-rich meteorites scattered across the Martian surface.
According to the researchers behind this study, it could take up to 10,000 times longer on Mars for oxidation to form than it does on Earth. This lack of rust on Mars likely means a corresponding lack of biological life, due to the fact that oxidation requires many of the same ingredients that life does:
[Martian] chemical weathering rates are ∼1 to 4 orders of magnitude slower than the slowest rates on Earth. Such extreme aridity leads to a drop in the abundance of microbial life to below detection levels even on Earth, as documented for example in the Atacama desert in Chile.
Lead researcher Christian Schröder with Stirling University in England hasn’t let this news deter his hopes that life might still be found on Mars deep under the surface:
[...] this latest research reaffirms just how dry the environment is today. For life to exist in the areas we investigated, it would need to find pockets far beneath the surface, located away from the dryness and radiation present on the ground.
Several recent discoveries are likewise indicating that the search for Martian life might be better reoriented to look underground where microbes are able to adapt to the harsh, nutrient-less environment by feeding on radiation. It might not be green-skinned humanoids with ray guns, but it’s a start.