March 18, 2019

Astro-Vid Of the Week: The Transit of Deimos

Phobos & Deimos as seen from MSL

Credit: NASA/JPL.

(Click here for full size view).

This past week saw the celebration of the one year anniversary of the landing of the Mars Curiosity rover at Gale crater. In just one year, the SUV-sized rover has revolutionized our understanding of the Red Planet.

And although it’s equipped to be a geologist, the Mars Science laboratory (MSL) has been a surreptitious astronomer on occasion as well. We routinely comb through the MSL camera archive and were recently surprised to find an image of the Martian Moons of Phobos and Deimos in one frame!

To our knowledge, this is a first. Sure, the MER rovers of Spirit and Opportunity have caught Phobos and Deimos in the Martian sky before, but this is the first documented conjunction of the pair. And heck, you can even see a tiny “half-moon” phase on both!

But there’s more. Fellow Universe Today contributor Ken Kremer and Marco Di Lorenzo of NASA/JPL-Cornell recently shared with us a short video of Deimos transiting the Sun as seen by Opportunity on Sol 3346, in what is probably our shortest yet video pick of the week:

The tiny potato-shaped moons orbit Mars in such tight orbits that transits from points somewhere along the surface of the Red Planet would be commonplace. But unlike our Moon, Phobos and Deimos are visually too tiny to eclipse the Sun!

There’s more astronomy in store over the next year for our Mars-bound ambassadors, as comet C/2012 S1 ISON passes the Red Planet in early October of this year. And next year, the rovers and spacecraft in orbit around Mars will get an even more breathtaking view, when comet C/2013 A1 Siding Spring passes only 73,000 miles above the surface of Mars on October 19th 2014.

This will be a first, a view of a comet from the surface of another world.

And the ultimate event? Stick around until November 10th, 2084 and well positioned Martian astronomers can witness a transit of Earth, the Moon and Phobos at the same time! Mark your calendars!


  1. [...] will pass 10.8 million kilometres from the planet Mars on October 1st, and may become the first comet observed from the surface of another world if NASA’s Mars Science Laboratory Curiosity can catch [...]

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