Tidal forces are dragging Phobos down? (APOD 3 Dec 2006)

[moontrail]

"Gravitational tidal forces are dragging it down. In 100 million years or so it will likely crash into the surface."

It seems to me that maybe the real cause could be the interaction with mars tiny atmosphere.

It´s not true that the future of our moon is just the opposite? Going away from earth.

Thank you.

[Pete]

Phobos orbits about 6000 km above Mars's surface, which is about one Mars diameter; the planet's already tenuous atmosphere probably wouldn't present much resistance. However, Phobos orbits Mars faster than Mars itself rotates (and, importantly, in the direction of Mars's rotation). Consequently, the tidal bulge on Mars lags behind Phobos because of the planet's relatively slow spin. the gravitational force of the bulge pulls "backward" on Phobos, decelerating the moon and draining it of orbital energy, causing its orbit to decay over time.

In a system where the planet spins faster than the satellite (Earth-Moon is a fine example), the tidal bulge raised on the planet by the moon is shifted in the direction of the planet's rotation; it pulls "forward" on the moon, increasing its orbital energy and expanding its mean orbital radius.

[kovil]

Great explanation Pete, it makes total sense to me !

Could the Mars tidal bulge from Phobos have any influence on the suspected geyser vents linked on another posting?

Do any Mars probes have seismic sensors for Marsquakes ?

Is there much seismic activity on Mars?

[Orca]

Great explanation Pete, it makes total sense to me !

Do any Mars probes have seismic sensors for Marsquakes ?

Is there much seismic activity on Mars?

If I remember correctly kovil, I don't believe there is much seismic activity on Mars. The core of the planet is thought to have cooled enough for volcanic activity to cease.

[moontrail]

Thanks Pete, Great explanation.