On Sunday, August 5th, NASA successfully landed a one-ton, $2.5 billion-dollar exploratory rover called Curiosity within Gale Crater, on the planet Mars. It was a picture-perfect landing and a remarkable achievement given the huge size of the payload, the extreme distance, and the unprecedented technical challenges involved. It is a success rightly celebrated by NASA scientists and engineers, as well as space buffs the world over.
Like many, I followed the news eagerly, but what caught my attention was the mission of the Mars Science Laboratory, as Curiosity is officially designated. One of it primary targets during the next two years of discovery is…carbon. Curiosity’s overall mission is not a new one: to discover if life ever existed on the Red Planet. This has been the subject of intense scientific and popular speculation for centuries, of course. It was the goal of previous explorations of Mars, including the famous Viking landings in the 1970s. But those inquiries “followed the water,” as one observer put it this week. The mission of Curiosity is different, it intends to “follow the carbon.”
According to NASA, this “mission of the decade” is looking for the building blocks of life as well as investigating how and why Mars turned from a wet and warm planet millions of years ago into the dry and cold place it is now. NASA chose Gale Crater specifically because it contains exposed layers of water-borne sediments, particularly on the slopes of three-mile high Mt. Sharp (named for an astronomer). Mars is similar to Earth in key ways and researchers want to know if it once hosted the elements necessary for microbial life. In other words, did it have a carbon cycle at one point, even a rudimentary one?
To find out, Curiosity brought along SAM – the ‘Sample Analysis Mars.’ SAM’s specialty is the detection of organic molecules, without which life is not possible. Organic molecules are made of carbon and hydrogen atoms, often called ‘hydrocarbons’ even though they can also include other elements, including oxygen, nitrogen, sulfur, phosphorus, calcium, and iron. These atoms can join together in a huge variety of ways, usually in long chains, which means millions of organic molecules potentially exist. SAM will investigate whether any are present in Gale Crater or on Mt. Sharp.
Here’s an image of SAM (courtesy of NASA):
SAM will be looking for isotopes in particular. Isotopes are versions of an element, carbon in this case, that are a little bit heavier because their nucleus contains more neutrons. For example, carbon-13 is an atom of carbon with an extra neutron, which makes it a heavier version of the more common carbon-12. Occasionally, a carbon-13 will take the place of a carbon-12 in an organic molecule. This is important since life tends to favor the lighter isotopes because their chemical reactions with them require less energy. So, if a Martian soil sample has more light carbon relative to heavy carbon than would be found randomly, this might suggest that life existed there at one time.
Here’s why all of this is important (from NASA’s web site):
“Mars today is a desolate world of cold and windswept deserts, apparently without life of any kind, at least on the surface. But there is evidence of a wetter (and possibly warmer) past – features resembling dry riverbeds and minerals that form in the presence of water indicate that water once flowed through Martian sands. Since liquid water is required for all known forms of life, scientists wonder if life could have risen on Mars; and if it did, what became of it as the Martian environment became more hostile, drying up and losing its magnetic shield, the atmosphere growing thinner, and the climate changing and growing colder. Hopefully, SAM will provide the some answers.”
It’s unlikely that there will be any potential lessons to learn from these experiments for us Earthlings, even as we face the spectre of a changing climate, since Mars’ climate appears to have changed as a result of intense volcanic activity long ago. But it will still be very interesting to follow Curiosity’s explorations and share in its discoveries as it follows the carbon. I’ll revisit this topic in future postings as developments warrant.
In the meantime, here’s a picture of Mars courtesy of Curiosity (kinda looks like New Mexico this summer!):