Hubble's Universe Unfiltered

  • September 12, 2013

    A Most Curious Solar Eclipse

    by Frank Summers

    It is not unusual for enthusiasts to make grand travel plans in order to observe solar eclipses. Friends of mine have journeyed to China, climbed one of the highest mountains in Mexico, and set sail to the middle of the ocean in order to witness these rare celestial events. Eclipse chasers say they are drawn to the incredible views of the solar corona as well as that indescribable feeling from the natural world as day slips into night and back again over a brief period.

    But no one travels farther to observe solar eclipses than NASA. One of the most famous solar eclipse shots was captured by Apollo 12 on the return flight back from the Moon. Passing through Earth's shadow, the crew captured a stunning image of a solar eclipse and were perhaps the first to use Earth as the occulting object. A similar and even more amazing image was taken by the Cassini Mission at Saturn. With the Sun in eclipse, the rings of Saturn were illuminated from behind and showcased as never before.

    NASA's latest solar eclipse tour de force comes from the Mars Science Laboratory, which everyone calls the Curiosity rover. The Curiosity team was able to position the rover to observe a solar eclipse by the larger of Mars' two moons, Phobos (the smaller moon is called Deimos). Given that Curiosity is a rover on the surface of Mars, and not a spacecraft that can fly into a shadow, that was some incredible feat of planning. Further, Phobos is a tiny moon (probably a captured asteroid) about 15 miles across -- much, much smaller, and with a correspondingly much, much smaller shadow, than the Moon, Earth, or Saturn.


    The above video shows the full timelapse sequence of 89 images captured by Curiosity, and is shown in realtime. It took just 32 seconds for Phobos to pass across the face of the Sun. The geometry of this eclipse makes it about as close to a total solar eclipse as is possible on Mars, with Phobos' silhouette as large as ever. The irregular shape of this tiny moon is brought out in sharp relief, allowing for more precise measurements of its size and orbit.

    While the visual image is not as spectacular as the Sun's corona or Saturn's backlit rings, the philosophical impact is just as deep. NASA is not just exploring the geography, geology, hydrology, etc., of Mars; we can also do astronomy observations from its surface. For those of us somewhat jaded by picture after picture of Mars' surface rocks, this image of a rock in Mars' sky is a great booster shot of awe and wonder.

    And, if you think this observation is something, just wait until they observe Comet ISON from Mars in the coming months. Doesn't that pique your curiosity?