unambiguous evidence that mars once had water
The Mars rover Opportunity discovered a vein of gypsum (calcium sulfate dihydrate), a soft mineral that can only be deposited by water. The discovery was made a few months ago, but the announcement was made on December 7th. There is a substantial body of evidence that supports water on ancient Mars — land formations that are congruent with shorelines, lake beds, other mineral deposits, and waterways. The presence of gypsum is the most conclusive so far, and the kicker is that gypsum is deposited by water with an acidity level that is more favorable for life than previously discovered minerals. (h/t Wired)
This is interesting news, but I’m personally waiting to see proof of water on modern Mars. It barely got a blip on the radar because of the summer government debt showdown nonsense, but back in August, researchers at NASA’s Jet Propulsion Laboratory in Pasadena presented images from the Mars Reconnaissance Orbiter revealing the seasonal appearance of what look to be water rivulets running down-slope at key points on the planet’s surface (GIF below). A study was concurrently published in Science.
While that evidence isn’t conclusive, it’s certainly supported by the fact that the water appears during the Martian summer (when surface temperatures swing from -10 degrees Fahrenheit to 80 degrees Fahrenheit. The locations of the streaks, near the equator, rather than the frozen poles, also adds plausibility.
Kim Stanley Robinson is probably loving this.