Free Astronomy Magazine July-August 2018

26 JULY-AUGUST 2018 ASTROBIOLOGY article published on June 8 th in the prestigious Science magazine (first author Jen Eigen- brode, of NASA’s Goddard Space Flight Center of Greenbelt, Maryland) confirms the presence of organic molecules on the surface of Mars. The discovery was made by NASA rover Cu- riosity, which identified those compounds in the powder produced by drilling holes in the clay sedimentary rocks of four different areas of Gale Crater. This large surface formation (154 km in diameter) originated over 3.5 bil- lion years ago from the impact of a small as- teroid; the depression created by the event was filled with water, turning it into a lake − this impact event produced the backdrop against which the sediments Curiosity has drilled into began to accumulate. NASA chose Gale Crater as an operating area for Curiosity precisely because it was hoping to discover at least some complex organic molecules − the building blocks of life. The drilling of the rover reached a depth of 5 cm, pulverizing rock layers that settled at least 3 billion years ago. A special device trans- ported the powder produced by the perfora- tions into a small oven, where it was heated to temperatures between 500°C and 820°C (930 – 1500°F). The gases produced by the heating of the powder were then analyzed by the SAM (Sam- ple Analysis at Mars instrument suite) mass spectrometer, which revealed the presence of small organic molecules, present in the spec- trometer as fragments of more complex or- ganic molecules that were not completely vaporized upon heating. Researchers found that some of those fragments contained sulfur, an element which under certain conditions can protect organic material from solar radiation and from aggressive substances such as per- chlorates, chemicals which are quite common on the martian surface. The results of the dust analysis also provided interesting information about the concentrations of organic molecules in the samples, which are on the order of 10 parts per million or more. This value coincides with the one obtained from the analysis of martian meteorites fallen on our planet and is about 100 times higher than the values pro- vided by previous measurements. The discovery of organic compounds on Mars, dating back to the times when the planet T his artist’s concept depicts NASA’s Mars 2020 rover exploring Mars. This mission is targeted for launch in July/August 2020 aboard an Atlas V-541 rocket from Space Launch Complex 41 at Cape Canaveral Air Force Station in Florida. [NASA/JPL-Caltech]