Stickney Crater
Credit: HiRISE, MRO, LPL (U. Arizona), NASA
Posted on 11/07/2009 6:00:56 AM PST by sig226
Explanation: Stickney Crater, the largest crater on the martian moon Phobos, is named for Chloe Angeline Stickney Hall, mathematician and wife of astronomer Asaph Hall. Asaph Hall discovered both the Red Planet's moons in 1877. Over 9 kilometers across, Stickney is nearly half the diameter of Phobos itself, so large that the impact that blasted out the crater likely came close to shattering the tiny moon. This stunning, enhanced-color image of Stickney and surroundings was recorded by the HiRISE camera onboard the Mars Reconnaissance Orbiter as it passed within some six thousand kilometers of Phobos in March of 2008. Even though the surface gravity of asteroid-like Phobos is less than 1/1000th Earth's gravity, streaks suggest loose material has slid down inside the crater walls over time. Light bluish regions near the crater's rim could indicate a relatively freshly exposed surface. The origin of the curious grooves along the surface is mysterious but may be related to the crater-forming impact.
so i would weigh a couple ounces on phobos?
If that moon ever had anything like an atmosphere, whatever created that crater eliminated it.
Michael Moore would weigh a slim trim 325 lbs on Phobos.
Phobos is far too small to have ever had an atmosphere.
Irish clergyman and social and political commentator, best known for his satirical fantasy Gulliver’s Travels, originally entitled Travels into Several Remote Nations of the World in Four Parts ... by Lemuel Gulliver (1726), in which reference is made to two (then undiscovered) moons of Mars. The astronomers on the flying island of Laputia, says Gulliver, have
... discovered two lesser stars, or satellites, which revolve around Mars, whereof the innermost is distant from the center of the primary exactly three of his diameters, and the outermost five: the former revolves in the space of ten hours, and the latter in twenty-one and a half.
When the two Martian moons, Phobos and Deimos, were eventually found, by Asaph Hall at the US Naval Observatory, their orbits proved to be quite similar to those described in Swift’s novel. Phobos is actually 6,000 km from the surface of Mars and revolves around Mars in 7.7 hours, whereas Swift gave the values 13,600 km and 10 hours, respectively. Deimos averages 20,100 km from Mars and orbits in 30.3 hours; Swift gives 27,200 km and 21.5 hours, respectively.
Probably a captured asteroid. I believe one if not both the martian moons are spiraling in.
Yes, and “Gulliver” immediately adds, “... so that the squares of their periodical times are very near in the same proportion with the cubes of their distance from the centre of Mars, which evidently shows them to be governed by the same law of gravitation that influences the other heavenly bodies.”
What’s NOT said, is that the constant of proportionality in Kepler’s Law, which he cites, depends on the mass of the central body, namely Mars. Swift’s numbers show that he had a good estimate in hand, and I’ve always thought he must have had help with this. I believe that he did belong to some sort of intellectual circle of friends, but I’ve never seen any comment from literary sources about Swift’s calculations.
...or Michael Moore.
Well that should make for an interesting show sometime down the road.
Don’t wait up for it.
Phobos, one of the three satellites in our solar system whose period (7h 39m) is less than the rotational period of the primary planet (24h 37m for Mars), is losing orbital energy to surface tides it raises on Mars. As the orbit of Phobos decays and gets closer to Mars, Phobos may eventually be torn apart when the tidal forces of Mars overcome the cohesive bond between its particles. Phobos, already inside the “Roche Limit” where internal gravity alone is too weak to hold it together, could conceivably become a ring plane about Mars within the next 50 million years. http://cmex.ihmc.us/CMEX/data/VOViews/MOONS.HTM
I’ll keep my eyes peeled. LOL
Gulliver’s travels was written in 1726 moons of Mars were not discovered until 1877 “Asaph Hall discovered both the Red Planet’s moons in 1877.” err?
Yes, but the fact is that Gulliver does give a detailed account of the discovery by the Laputians of two satellites of Mars, as described.
That Swift chose two as their number is not so amazing, and it is also reasonable that he made them to be close, because this way they are hidden from discovery by the brightness of Mars. He chose 3 and 5 Martian diameters as their orbital radii, whereas the actual values are 1.4 and 3.5, so ooh, way off! :-) But I think we have to accept that it was a lucky guess.
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