Mercury's surface dominated by volcanism and iron-deficiency

Scientists led by Brown planetary geologist Jim Head zeroed in on this kidney-shaped volcanic vent (at right and center), surrounded by a halo-like ring and a fainter outer ring, to help confirm that Mercury's surface had been formed by volcanic activity early in the planet's history. The image was taken by the MESSENGER spacecraft as it flew past Mercury in January 2008. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington