Pues en Nature no lo tienen nada claro. Según ellos: Martian ‘pebbles’ don’t prove watery past. Es más:
The best way to resolve the issue is to bring samples back from Mars, he says. Water-eroded rocks would probably be solid, while rocks from volcanoes or meteorite strikes would be filled with bubbles. «If the gas bubbles are sulphurous, [the rocks] are likely to be volcanic. But if they contain atmospheric gases, that’s good evidence that the glass was formed when a meteorite hit the surface,» says Mustard. NASA’s first Mars return mission is planned for 2011.