"Is Benner's story too kooky to believe? One thing's for sure: Benner is not a kook. He was one of the first chemists to voice skepticism about the claims for arsenic-based life, which stirred up such a fuss in 2010. ... This time, the wet-blanket role is filled by David Grinspoon, an astrobiologist from the Denver Museum of Nature and Science. Grinspoon, who's spending a year doing research at the Library of Congress, says that he's a "huge fan" of Benner's, but that his extraordinary claim isn't sufficiently supported by the evidence."
New Research Supports Theory That Life Started on Mars, Westheimer Institute for Science and Technology