in which NASA finds water on Mars

NASA has discovered water on Mars! There’s actual signs that liquid water is currently flowing on the planet, in tiny channels, before it evaporates.

If this past week’s news has given you a case of deja vu, there’s good reason for it. Over the past few years, NASA has made a string of announcements that all amount to “Water on Mars!” in popular press. Judging by the political cartoons and reactions on Twitter, etc, the general public has started catching onto the fact that NASA keeps making the same announcement over and over.

That’s a shame, though, because every time they’ve actually announced something different – an incremental improvement, but science rarely moves in leaps and bounds – all pointing to a gradually changing picture of Mars.

If you want to get down to it, it’s been known for years that Mars’s polar ice caps have both dry ice and water ice, so the fact that there’s ANY water on Mars hasn’t been a surprise for decades. But water locked up in an ice cap doesn’t say much for the rest of the planet.
1971: Mariner 9 enters orbit of Mars, and over the course of its orbits, it charts seasons and storms and spots things that look exactly like riverbeds on the Earth.
1998: Water on Mars! The Mars Pathfinder Rover’s first-person view of surface rocks suggests that they’ve been sculpted by water. It’s still possible there’s another reason (such as sculpture by air) but we already know Mars was once wetter.
2000: Water on the surface of Mars! The Mars Global Surveyor spots signs that water might be bubbling to the surface of Mars even today, in gullies near the base of Valles Marineris and deep craters, where the atmosphere is thickest and warmest. This is actually directly linked to this week’s discovery, which has been walked back and forth often.
2002: Water UNDER the surface of Mars. The Mars Odyssey space probe discovered permafrost under the surface. So, it might not be liquid, but there’s a lot of water just under the red soil even today.
2004: Liquid water once flowed on Mars. The Mars rovers Spirit and Opportunity (which landed in 2003) proved, through mineral analysis, that the rocks in the streambed-like shapes Mariner 9 saw were formed in the presence of water.
2005: This indisputable photograph from NASA’s Astronomy Picture of the Day.
2006: Water flowing down the sides of craters. Now seen in two high resolution pictures from the same spacecraft, and a lot harder to ignore than it was in 2000.
2008: That’s NOT water on Mars basically casting doubt on the 2006 and 2000 discoveries. The cascades down the sides of craters might just be “avalanches of dust”.
2008: The Mars Polar Lander confirms that it’s water ice near the poles.
2009: The legs of the Mars Polar Lander may have briefly been covered by liquid water before they froze. Or it might have just been frost.
2010: A study of river flow patterns shows where underground reservoirs used to be, and might STILL be, with liquid water.
2011: Further evidence of water flows down the sides of canyons on Mars, pushing back at the 2008 discoveries (and further arguments), this time using a computer model of salty water.
2012: The Opportunity Rover find proof that the rocks not only formed in the presence of water, they sat in MOVING water, and the rivers Mariner 9 saw really were rivers.
2013: The Curiosity rover discovers that there was a LOT of water in Galle Crater, and the entire thing was a deep freshwater lake.
2014: More work on the enigmatic seasonal finger-like formations further suggesting they are water flows, this time with spectroscopy showing iron features. This is from the same Georgia Tech team that announced something this year.
And now, in 2015, there’s confirmation that the spectroscopy of the little avalanches is consistent with leftovers from a salty brine once the water evaporates.

Are these all earthshattering and worthy of massive press releases? Perhaps not. But they are all different, and evidence of the incremental ways science proceeds with conjecture, tests, and proof. The most redundant things get amongst these observations is the crater-avalanches picture.
* first suggested in 2000 as being “recent avalanches”
* confirmed as such in 2006 when the same spacecraft saw changes in the crater walls
* refuted in 2008 when computer modeling suggested the streaks could just be dust avalanches,
* re-strengthened in 2011 when a better model suggested it was more likely to be salty brine,
* confirmed in 2014 and particularly 2015 when spectroscopy showed the composition of the streaks were what would be left over after salty water evaporated.

Ultimately, all of it adds up to this one thing: Mars is not a dead planet. Maybe not as alive as the romantic dying Marses of H.G. Well’s “War of the Worlds”, or Edgar Rice Burrough’s Barsoom, or Ray Bradbury’s “The Martian Chronicles”, but significantly more alive than we thought it was back when I was in school.

And NASA really needs a new headline.

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