Free Astronomy Magazine January-February 2023

T his image of the parachute that helped deliver NASA’s Persever- ance Mars rover to the Martian sur- face was taken by the rover’s Mastcam-Z instrument on April 6, 2022. [NASA/JPL-Caltech/ASU/MSSS] T he expanse of Jezero Crater’s river delta is shown in this panorama of 64 stitched-together images taken by the Mastcam-Z sys- tem on NASA’s Perseverance Mars rover on April 11, 2022, the 406 th Martian day, or sol, of the mission. [NASA/JPL-Caltech/ASU/MSSS] that might be embedded in a ring on your finger. Carbon is neither abundant nor scarce, making up just under 0.5% of all atoms in the entire universe. In a universe that is 75% hydrogen and 23% helium, being 25% of “everything else” certainly consti- tutes a nontrivial amount. The per- centages vary when we restrict the analysis to certain objects. Mete- orites, largely composed of iron and nickel left over from the formation of the solar system, are 1.5% carbon on average, with carbonaceous chondrites achieving higher per- centages due to the presence of or- ganic molecules and carbon-rich minerals. The Earth’s crust, domi- nated by oxygen and silicon, con- tains only 0.02% carbon. Turning to the carbon content of living organ- isms, we find humans are 18% car- bon by mass, exceeded only by the 65% oxygen mass that includes the water we carry within us – making this high carbon percentage a dra- matic localization of one element compared to the natural abun-