Earth and Moon, from Mars

Earth and Moon, from Mars

Earth and Moon, from Mars

Bad Astronomy
The entire universe in blog form
March 3 2008 6:13 PM

Earth and Moon, from Mars

The instant I saw the avalanche image from the HiRISE camera on-board MRO orbiting Mars, I knew I would have a contender for my Top Ten Astronomy Pictures of 2008.

Phil Plait Phil Plait

Phil Plait writes Slate’s Bad Astronomy blog and is an astronomer, public speaker, science evangelizer, and author of Death From the Skies!  

But then they released this one at the same time:

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Yeah, that's us. That's home. We were 192 million kilometers (115 million miles) from Mars when HiRISE turned around and took this picture. Right away I could tell that was South America's west coastline... which is incredible. I also was just starting to wonder about the Moon in the image when I read that it had been brightened artificially to make it easier to see; in general the Earth is 3-4 times more reflective than the Moon, so it's a lot brighter.

The Mars-Earth-Sun angle was just about 90 degrees when this was taken, which is why the Earth and Moon are half-full. Note that in reality, the Moon is about 30 Earth-diameters away from the Earth, so we're seeing some perspective here. The Moon was a day before third quarter when this was taken, so it was actually a bit closer to Mars than the Earth was when HiRISE snapped this picture.

Beautiful.