The case for ancient seas on Mars just got a little tighter. Already there is evidence of hydrated iron sulfate minerals on the Martian surface, as well as clays and limestone. According to new data from the NASA Mars Reconnaissance Orbiter, there is also opal.
Opal is a hydrated form of silica… it contains water dissolved among the silica molecules making up the rock, which is also non-crystalline at the molecular level, very much like glass. Opal can only form in the presence of water, and the new spectroscopic data show that large regions of the Martian surface are littered with the stuff. On top of the known presence of other hydrated minerals, this new discovery lends even more weight to the idea that Mars once had seas.
More significantly, where the opal deposits were found on Mars suggests they are fairly young, perhaps as little as 2 billion years old. That’s fairly late in the story for surface water on Mars, according to most models of how the planet has evolved over time to become barren, frigid and dry. The new information from MRO may force a revision of those models to allow a thicker atmosphere and a warmer surface to have persisted a lot longer. With Mars wetter for longer, the odds of life getting started there go up significantly, as do the odds of life getting impact-transported from Earth to Mars on meteorites.
Also, we now have a much better idea where Dejah Thoris might have gotten some of her jewelry…