Free Astronomy Magazine March-April 2021

MARS ROVERS volcanic hot spring. Cu- riosity allows scientists to more accurately de- termine the composition of the Martian atmos- phere, for example by measuring the stable iso- topes of elements such as carbon. Most ele- ments of biological in- terest have two or more stable isotopes. Organisms often selec- tively use particular isotopes based on their availability and mass, with L eft, the dark, stick-shaped features clustered on this Martian rock are about the size of grains of rice. This is a focus-merged view from the Mars Hand Lens Imager (MAHLI) camera on NASA’s Cu- riosity Mars rover. It covers an area about 2 inches (5 centimeters) across. Above, an exposure of finely laminated bedrock that includes tiny crystal- shaped bumps, plus mineral veins with both bright and dark material. [NASA/JPL-Caltech/MSSS] of it is likely trapped beneath the surface, frozen as ice or perhaps in liquid form if close enough to a heat source on the planet, such as a