@misc{indiciae6687a9be8d60,
  title = {Characteristics, distribution, origin, and significance of opaline silica observed by the Spirit rover in Gusev crater, Mars},
  author = {S. W. Ruff and J.D. Farmer and W. M. Calvin and Kenneth E. Herkenhoff and J. R. Johnson and R.V. Morris and M.S. Rice and R. E. Arvidson and J.F. Bell and P. R. Christensen and S. W. Squyres},
  year = {2011},
  doi = {10.1029/2010je003767},
  url = {https://pubs.usgs.gov/publication/70033934},
  note = {Source identifier: 70033934}
}