A Great Space Potato: Phobos Flyby Images

In April 2008 the Mars-orbiting HiRISE camera caught new high-resolution snapshots of Phobos.

HiRISE acquired two dramatic views of the Martian moon, Phobos, on 23 March 2008. Observation PSP_007769_9010, acquired at a distance of 6,800 kilometers from Phobos, provides surface detail at 6.8 m/pixel scale and a object diameter of about 3,200 pixels. The second observation, PSP_007769_9015 providing a closer look at 5,800 km, views the surface at slightly more detail (5.8 m/pixel with an object diameter of about 4,000 pixels).

The two images were taken within 10 minutes of each other and show roughly the same features, but from a different angle so that they can be combined to yield a stereo view.

Images from the  flyby of Phobos, on 7 March 2010. The images show Mars’ rocky moon in exquisite detail, with a resolution of just 4.4 metres per pixel. They show the proposed landing sites for the Phobos-Grunt mission.

Mars Express HRSC views of Phobos 10 March 2010ESA’s Mars Express spacecraft orbits the Red Planet in a highly elliptical, polar orbit that brings it close to Phobos every five months. It is the only spacecraft currently in orbit around Mars whose orbit reaches far enough from the planet to provide a close-up view of Phobos.

Like our Moon, Phobos always shows the same side to the planet, so it is only by flying outside the orbit that it becomes possible to observe the far side. Mars Express did just this on 7, 10 and 13 March 2010. Mars Express also collected data with other instruments.

via ESA – Space Science – Phobos flyby images.

Even better images of Phobos were obtained later:

The many faces of Phobos:

The next image shows the Mars-facing side of the moon, taken from a distance of less than 200 kilometres with a resolution of about seven metres per pixel during orbit 756, on 22 August 2004 by the ESA’s Mars Express spacecraft:

On Dec. 29, 2013 the European Space Agency probe Mars Express probe made a pretty gutsy move, passing just 45 kilometers (27 miles) above the surface of Phobos, the bigger of the two moons of Mars.  Phobos is only about 22 kilometers across, and Mars Express zipped by at several kilometers per second.

The images from HiRISE are the ones I like the best so far.

You could almost imagine walking on Phobos.

This little Mars moon is only 16 by 13 by 11 miles in diameter (27/22/18km). A writer for calculated that if you can do a two foot high jump on Earth (.5m), you could jump over a half mile (1.4 km) straight up on Phobos. It would take about 26 minutes, 13 minutes up and then 13 minutes back! The gravity would be different depending on where you are standing and the forces from the planet Mars would make a differences as well, according to some. You probably could not jump off of Phobos entirely, but you might be able to achieve escape velocity if you were riding a bicycle.

Just make sure you leave before the next 50 million years. The final fate of Phobos has been calculated. In 50 million years it will either crash into the planet Mars or it will be pulverized into a ring around that planet.


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One idea is that the big impact (deepest crater) fractured Phobos and along those lines the pits are sort of eruptions from the stress of that impact.


I wonder if anyone has a theory about what those rather regular and well-aligned stripes on the “potato” are caused by…

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