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| Image by © NASA Goddard Space Flight Center - Creative Commons Attribution - via flickr |
For nearly half a century it was believed that the solar system was home to only thirty two moons they ranged in size from Jupiter's moon Ganymede larger than the planet Mercury just small asteroids, like the Martian moons Phobos and Deimos that number has exploded in 2007 alone, scientists announced the discovery of twenty new moons around Jupiter, one around Saturn and three around Neptune.
What happened is astronomical telescopes had available to them what are called CCD cameras so these are digital cameras that almost everybody has novadays, it's difficult to hold astronomers to an exact number of moves in the solar system.
As cameras become more sensitive and telescopes more powerful, more moons revealed themselves.
Moons are classified in two distinct ways, those like our moons travel in nearly circular orbits, above their planet's equators and her cold regular moons, while our moon formed from any impact all other regular moons coalesced from the gaseous surrounding their parent planets a process known as accretion.
The classic example of regular moons who'd be the galley moons of Jupiter IOU roebuck, Ganymede and Callisto, the material that is going to form Jupiter too but extended a little bit, that material accumulates into the moons.
Moons that follow elongated orbits, highly tilted to their planet equators are called irregular moons, most of these moving retrograde clockwise if their planet rotates counterclockwise.
Phoebe the newly discovered moon orbiting Saturn is a perfect example, she began her life as an independent traveler orbiting the sun before being captured by the Saturn.
Either regular or hearing moons must fall withing the gravitational reach of their parent planets, this is known as the hemisphere, this phenomenon is named after George William Hill an American astronomer from the mid 1800's.
The moons of Mars, Deimos and Phobos operate very differently within the hemisphere, if the planet is rotating faster than the moon orbits like Deimos the title forces between the two actually show Deimos stop further and further, Phobos in the other hand is rotating faster than Mars rotates, these small moons were discovered by American astronomer Asaph Hall in 1877, he named Phobos after the Greek god of fear and Deimos for the god of terror.
Tom Duxbury was part of the Mariner 9 mission that first photographed the two potato shape moons in November of 1971.
Phobos is in a death spiral, it orbits just 3,700 miles from the martian surface closer to its host planet than any moon in our solar system, if our own moon is close to the Earth as Phobos is to Mars it would look twenty times larger.
Phobos predicament is caused by a process known as secular acceleration, as Phobos races faster than Mars rotates a title bump is raised on the Martian surface, in the process Mars yanks Phobos closer to its surface with each orbit, the struggle between Mars and Phobos is similar to the dynamics of a simple game of tetherball, imagine the ball as the moon, the pole as the planet and the rope between the pole and the ball as the planet's gravitational pull, what we see is that the gravity will pull the moon in such a way that it speeds up it goes faster and faster and it works its way until it eventually hits the pole, that's exactly what's happening to Phobos, Phobos is going around Mars faster than Mars rotates, that tidal interaction is pulling Phobos closer and closer in speeding it up in a sort of,
in about fifty million years we expect Phobos to be pulled in so closely it will impact Mars disappear as a moon of Mars, on the other hand Deimos the further out moon is going slower than Mars rotates and so its unwinding the string and the opposite way and what we see is Deimos is going further and further away from Mars and eventually Deimos will be pulled away from Mars by the gravity of the Sun, so over time Mars will become worthless.
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