June 24, 2018

Mars Cube One: Exploring Pale Blue Dot Redux

A ‘pretty pair…’ credit: NASA/JPL-Caltech.

What’s in a picture? A brand new robotic scout recently looked homeward, snapping a portrait of our place in space. The view was courtesy of the Mars Cube One mission, which launched with the Mars InSight lander recently from Vandenberg Air Force Base in California on May 5th, 2018. We’ve written on the technical aspects of the mission, and its list of groundbreaking firsts: the first interplanetary launch from Vandenberg, the first dedicated geology mission to Mars, and the first cubesats to venture beyond low Earth orbit. What we’d like to do is look at the astronomy of this simple image:

The annotated view from MarCO-B on May 9th, about 1 million kilometers out.

Credit: NASA/JPL-Caltech.

Sure, we’ve seen our homeworld from near and far before. Voyager 1 snapped the now iconic Pale Blue Dot image of the Earth caught in a sunbeam from 40.5 astronomical units (AU) or 3.7 billion miles out, which Carl Sagan waxed poetic about. Cassini has spied Earth from its perch around Saturn, Apollo astronauts have witnessed Earthrise from lunar orbit, and we’ve seen our fair world from planetary flybys too numerous to mention.

Maybe the Mars Cube One image is a bit underwhelming, sure. Meant as a pair of test-bed relays to chronicle the Mars Insight landing as they fly past Mars, MarCO-A and MarCO-B aren’t crucial to mission success, but will instead, show that carrying a such a small relay package to another world is possible.

The fish-eye lens image is akin to what your mobile phone camera would capture if you flung it over 600,000 miles out, over twice the Earth-Moon distance. Ever held your smartphone camera up and tried to catch an image of the Full Moon? You’ll get a similar result as the MarCO-B image above: a blurred bright dot a few pixels across. Smartphones are amazing, but you just can’t get around the tiny optical aperture and limiting resolution. That’s why large-lensed, DSLR cameras costing 5,000$ still persist.

But we still hold our phone up to the sky, wanting to share and document our little unique corner of time and space. And that is as you should: that view at that moment and place is yours and yours alone, and what MarCO-B captured teases humanity with its simple but enviable view.

There’s the blue marble of the Earth, shining at magnitude -14, way brighter than Venus at dusk. At 44′ across, Earth in this view is still actually larger than a Full Moon you’ll see next week on May 29th. The fainter but still respectable -10 magnitude, 15′ diameter Moon about 10 degrees off to the left shows a stark contrast due to is grayish albedo, about the reflectivity of worn asphalt. Two worlds hanging in space, that couldn’t be more different.

Even the Sun-shadow angle on the High Gain Antenna Feed off to the right gives us clues to the scene, as the squashed pixels of the Earth just show a tiny hint of a gibbous phase. It’s also worth remembering that no person has thus far ventured out farther than this Earth-Moon stage, the backdrop for the drama of all of humanity… at least, not yet.

MarCO-A and MarCO-B will also give us brief glimpses of Mars on flyby day later this year on November 28th 2018, as they pass just 2,175 miles from the Red Planet, an enviable view that humans may one day witness for themselves… sure, a postcard is great, but there’s something to be said for being there, in person.

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