The Mars-like deserts of the American Southwest are some of Earth’s most iconic stargazing grounds. Far from pestering city lights and free from regular cloud cover, they provide a starry-skied sanctuary for lovers of the night.
So, it would stand to reason that the deserts of Mars itself would be even more idyllic. After all, there’s no light pollution and cloud cover is hard to come by.
And to some degree, that’s true. It doesn’t get much darker than nighttime on the Red Planet. And Mars’ atmosphere is so weak — just one percent of Earth’s — that the stars don’t twinkle.
Dust Trouble
But the Red Planet provides
another complication: dust. Even straight overhead at zenith — the region where atmospheric interference is the least — the dust decreases a star’s brightness by one whole magnitude. That gets drastically worse toward the horizon, where dust can dim stars by as much as 4 magnitudes.
Astronomers know this from watching the night sky with the Mars rovers, which have cameras about as sensitive as the unaided human eye. When the sky is perfectly clear, NASA’s Opportunity rover can just make out magnitude 6 stars — generally considered the limit for human viewing.
A Rover's Eye View
Astronomers have turned those rover eyes toward the heavens to watch lunar eclipses and comet flybys. In 2014, NASA’s Curiosity rover
caught Comet Siding Spring (C/2013 A1) as it buzzed Mars at a distance of just 87,000 miles. That’s 10 times closer than the famous Comet Hyakutake (C/1996 B2) that squeaked passed Earth back in 1996. It even
messed with Mars’ magnetic field.
NASA’s Maven orbiter shows that the more dramatic result was a meteor shower that peaked at thousands per hour, or maybe even tens of thousands. That’s more dramatic than anything in recorded history on Earth. But the dust would have obscured many of those.