Take a look at that rock face. It measures about 8 inches (20 cm) across and was probably deposited as sediment in a Martian stream millions of years ago. Look more closely and you’ll spot veins filled with a white material. Scientists think the rock was later fractured. Mineral-laden waters flowed through the cracks, depositing their burden and filling the cracks.
Last month the Curiosity rover extended its robotic arm and drilled into a fine-grained, sedimentary rock layer called Sheepbed in Mars’ Gale Crater. A sample of the powder was delivered to the rover’s onboard chem lab, analyzed and found to contain very familiar-sounding elements - a soup of carbon, sulfur, phosphorus, hydrogen, oxygen and nitrogen. Living forms love and need them all to thrive. Why are these elements so important? I’m glad you asked:
* Sulfur – certain kinds of bacteria thrive by breaking down sulfur compounds to produce their “food”. Sulfur is also found in amino acids which are the building blocks of proteins. You, me and everything alive are built from proteins.
* Phosphorus – an important component of our DNA and RNA and also an essential element in a chemical compound called ATP. ATP (adenosine triphosphate) is used to transfer energy inside the cell and metabolize nutrients to create energy.
* Nitrogen – another essential ingredient of amino acids. Bacteria living in the roots of plants take atmospheric nitrogen and convert it into a form plants can use so they can thrive. Animals and humans get their nitrogen in turn from plants or from other animals that eat plants.
* Carbon – is the basis for all organic life as we know it. It’s an essential part of our DNA and RNA. Carbon has the unique ability among atoms to bond to almost any molecule. We get the carbon we need through plants (or other plant-eating animals) which take carbon dioxide in the air and convert it into the carbon molecule called “glucose” (food).
* Hydrogen – hydrogen happily latches on to oxygen to form water (H2O) which is another life essential.
* Oxygen – a must-have for respiration. It “oxidizes” or “burns” foods to create energy. Most life forms on Earth require it to live.
The rock also contained clays and sulfates, evidence that the materials that it was originally deposited by running water, perhaps a stream, and later solidified into rock. Better yet, the water was neither acidic nor alkaline but “neutral” much like freshwater on Earth. Indeed you could have slaked your thirst with it had you been around then.
Taken together, these signs point to a wetter, warmer Mars in the distant past, and a planet that could have supported life. Today it’s a cold, dry desert with air less than 1% as thick as Earth’s and toasted by toxic ultraviolet light from the sun.
While no complex organic molecules like amino acids, fats and sugars have been found so far by the roving robot, all the basic ingredients are there in Gale Crater to create them.