I couldn't not blog about this

[mmcirvin]

So, New Scientist, your source for amazing revolutionary discoveries in science whether they are true or not, ran a story about the discovery of liquid puddles on Mars that immediately rang alarm bells in my head.

The person making the claim was Ron Levin, son of Gilbert Levin, a scientist with the 1970s Viking lander project who's long claimed that his experiment detected life on Mars. Who knows—maybe it did. But both of the Levins have also claimed for a long time that the color balance of every picture from the surface of Mars is way off, and the planet actually has a blue sky and green vegetation-like patches on the rocks—a claim that had a germ of truth to it, in that the Viking pictures often did have bad color balance (Mars does not have a Pepto-Bismol-colored sky), but this can't reasonably be said of the Pathfinder or rover photos. So I'd been inclined to wait for independent corroboration for this latest claim.

Anyway, now it turns out that the "puddles" are on the slope of a crater wall.

Comments

[acw.livejournal.com]

Another possibility is to take the average color and warp it to 50% gray, then amplify deviations from the average. I suppose somebody must have done that.

[mmcirvin.livejournal.com]

It's an interesting question whether, under color constancy/retinex theory/what have you, your visual system would actually do that, though. Maybe it would if you could see absolutely nothing but sky and rocks, but you could presumably also see your own body in whatever sort of Martian survival getup you are wearing; and we also know from the calibration targets on the probes that overall ambient lighting isn't affected enough to color foreign objects consistently with the yellow-tan color of everything else. I'm guessing that if you were actually there, your surroundings would still look Sedona-red-rock colored with a more or less tan sky, but it's a difficult question.

[acw.livejournal.com]

Yeah, that sounds plausible. Rats. I'd still like to try that process ... amplify the deviations from average. But you're right that it's probably not a good clue to what you'd actually see.

[mmcirvin.livejournal.com]

"Stretched color" images actually are used pretty often by the JPL teams to look more closely at color variations; you can see a fair number of them on the rover website--they're the ones with a gray or purple sky, and the little concretions in the Opportunity Meridiani Planum pictures are sky-blue--but there isn't any attempt to keep the average hue constant, I think.