This is just really cool – a time-lapse animation from the Hubble telescope showing a tiny moon zinging around Mars

By Tom Yulsman | July 21, 2017 5:06 pm

The tiny Martian moon Phobos orbits the Red Planet in this animation of images from the Hubble Space Telescope. Please click the animation to enlarge it. (Source: NASA, ESA, and Z. Levay (STScI)

On May 12, 2016, when Mars was 50 million miles from Earth, the Hubble Space Telescope turned its incredibly sharp eye toward the Red Planet. The time-lapse animation above reveals what it saw.

That little white speck zinging around Mars is Phobos, a football-shaped moon just 16.5 miles by 13.5 miles by 11 miles. You’re seeing it in an animation consisting of 13 separate exposures by Hubble.

Phobos looks like it is speeding along at an unbelievably rapid clip. In reality, Hubble acquired the 13 frames over the course of 22 minutes. So things are really sped up in the time-lapse.

Even so, Phobos is something of a sprinter. As NASA puts it:

The little moon completes an orbit in just 7 hours and 39 minutes, which is faster than Mars rotates. Rising in the Martian west, it runs three laps around the Red Planet in the course of one Martian day, which is about 24 hours and 40 minutes. It is the only natural satellite in the solar system that circles its planet in a time shorter than the parent planet’s day.

And this is pretty cool too:

Orbiting 3,700 miles above the Martian surface, Phobos is closer to its parent planet than any other moon in the solar system. Despite its proximity, observers on Mars would see Phobos at just one-third the width of the full moon as seen from Earth. Conversely, someone standing on Phobos would see Mars dominating the horizon, enveloping a quarter of the sky.

For more on Phobos photobombing Hubble’s observations of Mars, as well as information about the moon, missions that have observed it, and much more, check out the video above from NASA.

  • Mike Richardson

    The orbit of Phobos is also decaying, which is why it’s so rapid, and getting faster — just think of the coin donation funnels at a shopping mall, which speed coins down a ramp to spiral inwards until they eventually drop into the bucket. Likewise, Phobos will continue to tighten its orbit, and in 30-50 million years (estimates vary, but it is inevitable), the small moon will either be torn apart when it’s proximity to the Martian surface falls within the Roche limit, or it will impact Mars at a shallow angle. Either way, it will go out in a blaze of glory.

  • OWilson

    Another interesting fact about the Martian Moons is that In a “thought experiment” worthy of Einstein, or Slipher who predicted Pluto, Jonathan Swift, in one of his books, described two moons of Mars that were very similar in size, orbit, and period, some 150 years before they were actually discovered.

    They named a crater on Demos after him. :)

  • jonathanpulliam

    The god of war was Mars.

    Interminable, non-cost-justifiable, poor value-for-the-money war and conflict, designed to succor the insatiable U.S. Military Industrial Complex with its pronounced “phobia” against winning, renders it a virtual inevitability that Mars, in due time, will strip NASA fraudsters of their budget and hence their very existence.

    • OWilson

      They are already strapped!

      Obama had to “collude” with Putin to get a ride for our astronauts to the Space Station!

      He told his NASA Director that the top priority was “Muslim Outreach” :)



ImaGeo is a visual blog focusing on the intersection of imagery, imagination and Earth. It focuses on spectacular visuals related to the science of our planet, with an emphasis (although not an exclusive one) on the unfolding Anthropocene Epoch.

About Tom Yulsman

Tom Yulsman is Director of the Center for Environmental Journalism and a Professor of Journalism at the University of Colorado, Boulder. He also continues to work as a science and environmental journalist with more than 30 years of experience producing content for major publications. His work has appeared in the New York Times, Washington Post, Audubon, Climate Central, Columbia Journalism Review, Discover, Nieman Reports, and many other publications. He has held a variety of editorial positions over the years, including a stint as editor-in-chief of Earth magazine. Yulsman has written one book: Origins: the Quest for Our Cosmic Roots, published by the Institute of Physics in 2003.


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