Planetary Society logo
  • “Exploration is in our nature.” - Carl Sagan

Opal halos around cracks in Gale Crater on Mars

Opal halos around cracks in Gale Crater on Mars
Opal halos around cracks in Gale Crater on Mars This image taken by NASA’s Curiosity Mars Rover in 2015 shows “halos,” pale material around fractures in the bedrock in Gale Crater. The halos are comprised of silica and opal, a water-rich silica-based gem. The presence of opal on Mars suggests long-standing wet conditions in the crater’s past. NASA/JPL-Caltech