Yellowknife Bay is a rocky plain, a sepia-colored dustbowl surrounded by the brown silhouettes of low mountains. But three billion years ago it was covered in freshwater streams and lakes – and there was snow on the mountains. This is the newest discovery from NASA’s Rover Curiosity, and it is the most hopeful sign yet that life might once have existed, and flourished, on Mars.
Analysing a sample of rock with a laser and an x-ray beam, the Curiosity detected clay minerals and other elements that form exclusively in fresh water. This is a breakthrough discovery because previous samples, which were taken in other locations on Mars, were less than encouraging. A 2008 sample by the Opportunity rover held signs of liquid water, but it appeared to be a salty brine high in sulfuric acid – unsuitable for life. The water in Yellowknife Bay, in contrast, would even have been drinkable. It also contained carbon, oxygen, and sulfur molecules, which are the building blocks and energy sources of primitive life.
On the NASA website, lead scientist Michael Meyer said that “A fundamental question for this mission is whether Mars could have supported a habitable environment. From what we know now, the answer is yes.”
The Curiosity will be hidden behind the Sun until May, when scientists will continue drilling. The rover will leave Yellowknife Bay and travel to the center of the Gail Crater, taking samples as it goes. Its next mission: determining how amenable Mars could be to human life. NASA plans to send astronauts to the planet in 2020.
Scientists have known for decades that Mars contains large quantities of water, mainly locked into thick polar ice sheets. Because of the low atmospheric pressure, liquid water exposed to the Martian air would most likely boil away, even in the freezing temperatures. But in the past Mars had a protective magnetic field and tectonic activity. Water in underground wells would have risen to the surface in scalding volcanic eruptions.
Some optimists even hope that water has remained liquid underneath the surface, in which case a Jules Verne-esque scenario is possible, in which life long dead aboveground may have survived below it. John Parnell, a professor at the University of Aberdeen, co-authored a paper published in January suggesting that Mars may in fact resemble Earth in a zone up to 5 kilometers deep. Life here would not be little green men – it would resemble the primitive micro-organisms found in Earth’s own deep-sea caverns. But it would probably come in peace.
Photo: Flickr Commons