Stardate 20010613.1454 (On Screen): The Earth has a tendency to change things. A bone or piece of wood which is buried in the proper environment for a million years can be profoundly changed chemically, with its carbon or calcium and phosphorous being replaced by silicon. This kind of change happens slowly, atom by atom, and the structure of the bone or wood is retained even on a microscopic level. But it's not possible to chemically evaluate such a fossil to determine anything at all. Liquid water does that kind of thing, and it happens to be the case that there is a great deal of liquid water on the surface of the Earth everywhere, and always has been.
I understand that researchers are almost desperate to learn things about Mars, and that the presence of rocks on the Earth which came from Mars represents a unique opportunity to learn things about that planet, at least until such time as some mission actually retrieves real ones for us. But the prospects for that are dim for the forseeable future. Still, it is important to keep scientific perspective. These researchers can't reasonably assume that the distribution of Protium and Deuterium in this particular rock hasn't changed in the tens of millions of years that it has been exposed to weather on the Earth. "We detected a very low deuterium/hydrogen ratio, close to a reading for the Earth." Small wonder, considering how long it's been sitting on this planet. (discuss)
