NASA’s Mars Rover Curiosity discovered plentiful indigenous spherical ooids at High Dune and Namib Dune in Bagnold dune field, Gale Crater, Mars. Closely resembling ooids of Earth, the Martian ooids are spherical in shape, similar in size, mostly about 0.5 mm in diameter. Colors of the Martian ooids are various, including white, yellow translucent, green, grey, and yellow. The Martian ooids should have been formed by microbes, because ooids of Earth have recently been found to be formed by microbes and microbial borings are found in ooids of Earth and Mars. The Martian ooids are unlikely to have been formed by non-biological mechanisms, because there was no highly agitated water at the discovery sites.