Earth from Mars…

Ok, I should make this clear from the start that this is NOT a post about Opportunity, or even Curiosity, taking an image of Earth from the surface of Mars. It’s inspired by an image NASA released a few days ago showing the Earth and Moon as seen from Mars, but from orbit, not from the surface. The image was taken by the HiRISE camera onboard the Mars Reconaissance Orbiter. Here it is…


Here’s how the NASA website described the image:

The image combines two separate exposures taken on Nov. 20, 2016, by the High Resolution Imaging Science Experiment (HiRISE) camera on NASA’s Mars Reconnaissance Orbiter. The images were taken to calibrate HiRISE data, since the reflectance of the moon’s Earth-facing side is well known. For presentation, the exposures were processed separately to optimize detail visible on both Earth and the moon. The moon is much darker than Earth and would barely be visible if shown at the same brightness scale as Earth.

The combined view retains the correct positions and sizes of the two bodies relative to each other. The distance between Earth and the moon is about 30 times the diameter of Earth. Earth and the moon appear closer than they actually are in this image because the observation was planned for a time at which the moon was almost directly behind Earth, from Mars’ point of view, to see the Earth-facing side of the moon.

So, it’s not actually one image, its two, combined, and it has been tweaked to make the Moon brighter than it would actually appear. That’s ok, we tweak space images all the time; as long as we explain what we’re doing, and why, it’s fine.

Seeing that image – and you couldn’t avoid seeing it; it was everywhere online within hours of NASA releasing it – got me thinking about were Earth would have been in Opportunity’s sky when it was being taken by the orbiter high above it. Firing up Stellarium I found that Earth would have been a bright “Morning Star” in the east, shining to the lower left of Mars’ moon Deimos, which would have been much brighter…


Let’s put some labels on that…


I love the idea that Opportunity could have seen Earth shining in the sky as a bright blue “star” as HiRISE was taking that image. But what I love even more is the idea that one day people will stand on Mars and see Earth shining in the sky like a star, and if they have a telescope will be able to see views just like the one in the HiRISE image. It’ll be a curiosity for the first explorers, sure, but eventually there will be settlers and colonists on Mars, families, with children, native-born martians, and no doubt their science teachers will take them outside and show them Earth through a telescope, looking like this…


“Wow…!” some will gasp, “Earth… look how blue it is… it’s beautiful… !”

“Yes, that’s it,” the teacher will nod, “the Homeworld…”

“Not mine,” one child will say defiantly, staying away from the queue to look into the eyepiece. “Mars is my Homeworld…”

And it will be.


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1 Response to Earth from Mars…

  1. Eric Hahn says:

    Cool post. . .

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