The Mars of today is a barren and inhospitable place for living things, but scientists think it may have been very different in the past. One of NASA’s aims with the Curiosity Rover is to search for signs of ancient life on the red planet. The rover has returned a lot of fascinating science, but its latest discovery offers the best evidence yet for life on Mars. Curiosity has detected large organic molecules inside ancient Martian rocks, as well as methane cycles currently active on the planet.
NASA has been searching for confirmation of organic molecules on Mars since the 1970s when it sent the Viking landers to the planet. Now Curiosity shows that these carbon-based compounds do indeed exist. The rover spotted the chemical signature in samples take from sedimentary rocks the formed some 3 billion years ago.
Organic molecules are considered one of the basic building blocks of life. The compounds discovered on Mars could have been produced by living things, or they could have been food for those living things. This doesn’t constitute proof that life existed on Mars, though. Other processes that have nothing to do with living organisms can create organic compounds as well. Still, this discovery is very encouraging in the context of what we know about Mars in the distant past.
NASA has good evidence that Gale Crater where Curiosity is rolling around used to be a lake. The planet had a thicker atmosphere at the time, and the presence of organic molecules suggests life could have had the necessary pieces to get going. We might find even more evidence in future missions, too. Curiosity can only drill a few centimeters into Martian rocks, and it lacks the advanced tools necessary to search for more complex markers of life.
In addition to the continued search for ancient life, NASA will have to take a closer look at the current Martian atmosphere. Curiosity reports that methane levels on Mars go up and down in a predictable cycle. Methane levels reach 0.6 parts per billion during the summer, but that number is only one-third as high during the winter season. No one knows what’s making this methane, but scientists speculate that it’s released from underground pockets.
NASA will use both these discoveries to inform the design of its upcoming Mars 2020 rover. The 2020 rover will include an advanced spectrometer to scan for organic molecules. The ESA’s ExoMars rover, which is targeting the same time frame, will assist with the search for ancient life.
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