I don’t care about the math and statistics. I went looking for visual comparisons, where image exposure is adjusted to show how a sunny day on both planets really compares, but I didn’t find anything.
During the last partial solar eclipse in SoCal, I thought, “I wonder how close this really is to how Mars feels.” It was eerie (as always) with a clear sky, and sun near noon, but feeling colder than I should (obviously Mars is FAR colder), and with dimmer light.
Our eyes have an enormous dynamic range. That is not exactly intuitive to most people. Still, I was hoping to find some way or reference that captures the experience of the sun on Mars, and really the emotional impact of what it means to stand on Mars at solar noon with human eyes.
Our pictures of Mars are all adjusted for optimal exposure, but that makes it intuitively seem very Earth like when in reality it is like a next level Neo Exo-Antarctic, even under the warmest of days under direct sunlight. What is that really like?
Excellent question. From first principles: mars is about 1.5 AU from the sun. Using the intensity equation (inverse square law), Mars should receive about 1/(1.5x1.5) the amount of solar radiation, or about 44% on average.
Earth gets about 1400 W/m² hitting the top of the atmosphere, but most places on earth only see about 1000 W/m² after the column of air absorbs a bunch of it. Martian air absorbs almost nothing (being very thin), so you’d expect to see about 44% of 1400W/m² – or about 600W/m².
A quick Google search for “mars solar intensity” shows a result of 590 W/m², so that is pretty close to accurate, from first principles.
So 60% as bright, if talking pure intensity. As you say, the human eye has a pretty responsive dynamic range, and this is quite an acceptable number.
For point of comparison, this is the difference between the sun at high noon versus the sun at 4pm for most of the world. On Mars, high noon would have a solar intensity more like 4pm on earth. No where close to your darkness experience with the eclipse.
Excellent answer! Sciency enough and a very tangible comparison.
Since you answered it, I figured I’d add that on the dark sides, Earth and Mars likely have similar light levels(ignoring the moon and light that’s bent through the atmosphere)
With regards to the eclipse it would depend on how much of the sun is covered though. I’d assume it’d about the same as you’d get during a partial eclipse when the sun is 40% covered?
Effectively, yes