Astronomy Picture of the Day 4-06-03

NASA ^ | 4-06-03 | Robert Nemiroff and Jerry Bonnell

[petuniasevan]

Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2003 April 6

Phobos: Doomed Moon of Mars
Credit: Viking Project, JPL, NASA; Image mosaic by Edwin V. Bell II (NSSDC/Raytheon ITSS)

Explanation: This moon is doomed. Mars, the red planet named for the Roman god of war, has two tiny moons, Phobos and Deimos may well be captured asteroids originating in the main asteroid belt between Mars and Jupiter or perhaps from even more distant reaches of the Solar System. In this 1978 Viking 1 orbiter image, the largest moon, Phobos, is indeed seen to be a heavily cratered asteroid-like object. About 17 miles across, Phobos really zips through the Martian sky. Actually rising above Mars' western horizon and setting in the east, it completes an orbit in less than 8 hours. But Phobos orbits so close to Mars, (about 5,800 kilometers above the surface compared to 400,000 kilometers for our Moon) that gravitational tidal forces are dragging it down. In 100 million years or so it will likely crash into the surface or be shattered by stress caused by the relentless tidal forces, the debris forming a ring around Mars.

[petuniasevan]

Phobos is also the subject of the 3-29-03 APOD.
Phobos' statistics are listed on that thread.

What would you weigh on Phobos? Very little indeed. Using the acceleration due to gravity as a guide, it can be demonstrated that Phobos' gravity is 1485 times weaker than Earth's! Unbelievable as it may seem, a person weighing 150 lbs. on Earth would weigh only 1.6 OUNCES on Phobos!

Could you jump OFF Phobos? Not likely. Its escape velocity is 11.5 meters/second: about 26 MPH. Your attempt would leave you hanging in a decaying orbit for an extended period of time, though. Better bring that Snickers bar Mars bar!

Other side of Phobos (Viking photo)

[petuniasevan]

[boris]

Possessives of planetary bodies:

Pertaining to or of Mercury: Mercurian?
Pertaining to or of Venus: Venusian (not venereal!)
Pertaining to or of Earth: Terran
Pertaining to or of Earth's Moon: Lunar, perhaps "Cynthian"
Pertaining to or of Mars: Martian
Pertaining to or of Jupiter: Jovian
Pertaining to or of Saturn: Saturnian (not Saturnine!)
Pertaining to or of Uranus: Uranian
Pertaining to or of Neptune: Neptunian
Pertaining to or of Pluto: Plutonian

Pertaining to or of Phobos:
Phobone?
Phobosian?
Phobonian?
Phoboan?
Any or all of the above?

--Boris

P.S. There is a town or city in the United States named after every planet, except one. Yup. Uranus. Firstly, nobody wants to live in Uranus, and secondly nobody wants to ask directions: "Hey buddy, how do I get to Uranus?"

[petuniasevan]

Pertaining to or of Venus: Venusian (not venereal!)

Venereal - that's another area of human endeavor :-P

I'm guessing that the possessive of Phobos is Phobian.

[petuniasevan]

But there IS a Uranus, Antarctica!

Their weather is not too Uranian.

http://www.wunderground.com/global/stations/89264.html

[firewalk]

Thanks for the ping (-:

[sistergoldenhair]

Thanks!

[mikrofon]

If you're afraid of this moon are you phobophobic?

I guess it can also be said that the Sun is possessive of planetary bodies...

Great job as always with APOD!

[RightWhale]

Phobos would be a great place for the first manned Mars base.

[boris]

Phobian, eh?

Sounds a little psychiatric to me.

My favorite word (invented) is: aibohphobia, the morbid fear of palindromes--and the only word which causes the disorder it seeks to describe.

Also arachibutyrophobia, the fear of having peanut butter stick to the roof of your mouth.

--Boris