[X] My Assistant

[djellison]

Expect a quiet few sols - http://www.lpl.arizona.edu/~lemmon/mars-tau-b.html
SOL TAU
5097 0.65
5098 0.64
5099 0.67
5100 0.64
5101 0.60
5102 0.60
5103 0.61
5104 1.55
5105 ****
5106 2.12

[Deimos]

Exactly! The Sun itself was fainter than a full moon on Earth on Sunday. But in each photon-dust interaction the extinction (which tau measures) is <10% absorption and >90% scattering to sky light. The scattering is ~85% downward, 15% upward. There would be 10-11 extinction events (more like 14-15 at the time Opportunity was awake, with the Sun not vertical). Modeling literally the round numbers I just used, I get 98% loss of light at the surface (i.e., sky light >10,000 times direct sun light); you got 97% (and I believe the panels more than made up numbers).

What did it look like? Other than the decidedly ruddy to brownish tint, it looked like a somewhat overcast day. The sort of mid-afternoon when you can just barely see (or not quite see) the Sun through clouds that stretch from horizon to horizon. When the world would be black through eclipse glasses, but easily visible without. Normal human vision would adapt well--it's not night, moonless or moonlit, or even sunset. Solar panels, however, are not known for being so dark-adaptable. So the drama is real, even if people seem to want to describe it in terms that would be as dramatic for people as the actual situation is dramatic for the rover.

This weekend, I expect tau of several hundred. Not on Mars, but at home, where we expect thunderstorms.

PS, scattered light is not 'neglected'. In photometrically measuring opacity it is hunted and eliminated with extreme prejudice.

[mcaplinger]

Solar panels, however, are not known for being so dark-adaptable.

As a data point, I have solar panels on my house. On a typical day in March they generate about 30 kW-h. During the cloudiest, lowest-production day this March, I got about 3 kW-h, about 10x worse.

700/22 is 32x less production, so this would be a really cloudy day, at least by SoCal standards. (Solar distance is already scaled out so don't complain about that.)