Questions tagged [phobos]

Questions about Phobos, the larger of Mars's two moons.

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Which is closer to the Earth, Phobos, Deimos or Mars? [closed]

Which one is closer to the Earth, Phobos, Deimos or Mars? None of the answers that I find actually answer my question.
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-1 votes
1 answer
158 views

Phobos and Deimos tidal locked?

Are Phobos and Deimos tidally locked to Mars?
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3 votes
1 answer
198 views

How long before Phobos reaches the Roche limit of Mars?

Phobos orbits really close to Mars, so close that one Phobos period is shorter than one sol. Due to tidal friction, it is also getting closer and closer to Mars. How much time will it take before ...
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2 votes
1 answer
64 views

How did the orbits of Phobos and Deimos circularize?

The satellites of Mars might be captured asteroids. But Phobos has an eccentricity of $0.015$, and Deimos of $3\times10^{-4}$. If they were captured, they likely were captured with rather eccentric ...
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4 votes
0 answers
42 views

Has the inclination of the orbital plane of Phobos and Deimos followed that of Mars' axial tilt?

Phobos and Deimos are very close to Mars' equatorial plane (the inclination of their orbits is roughly 1°). The axial tilt of Mars has changed a lot over time, and might have had a inclination of over ...
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11 votes
2 answers
2k views

How many satellites orbit their planet faster than the planet rotates?

Phobos is so close to Mars that it orbits Mars much faster than Mars rotates. This means that it rises in the west and sets in the east, even though its orbit is prograde. Are there any other known ...
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5 votes
1 answer
127 views

Eclipses on Mars

This amazing video shows an annular eclipse of the Sun by Phobos as seen from Curiousity. This one shows an eclipse by Deimos. My question is do these things ever both happen at once? Do you ever get ...
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5 votes
1 answer
550 views

Mars night sky -- Phobos and Deimos?

I'm having a debate about how bright Martian nights would be, in terms of both the sky itself and ground illumination. This answer seems to indicate that the stars would be only dimly visible, and ...
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3 votes
1 answer
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How do we know that a natural satellite cannot be a hollow object?

In their 1966 book, Intelligent Life in the Universe, Carl Sagan and Iosif Shklovsky state that "a natural satellite cannot be a hollow object." How do we know this is absolutely true?
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1 vote
1 answer
274 views

When Phobos collides with mars (or breaks up), will it have any noticeable effects on Earth?

When Phobos meets its predicted doom in a few 10s of millions of years, whether it breaks up or collides with the surface of Mars, will this change have any noticeable effects (permanent or temporary) ...
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5 votes
1 answer
465 views

Formation and capture of Mars' moons, Phobos and Deimos

Mars's moons have the appearance of captured asteroids. How could this capture have taken place. An asteroid in solar orbit would need to loose some momentum to be captured. The gas Giants can ...
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8 votes
2 answers
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How does gradual crossing over of the Roche limit transform a planet or moon?

Some cartoon simulations (an example) of an object (assume here a large moon with Earth-like density) which crosses the Roche limit of a much more massive giant planet, illustrate a circle suddenly ...
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