I have been thinking about how water was once on the surface of Mars. Today there is no evidence on water on the surface only 'channels' of were water once flowed.
I guess, water is still on mars but under the ground.
Could an asteroid have brought the water up to the surface, then after the asteroid has passed the water sinks back under the subsurface of mars ?
If a massive asteroid passed close by the planet mars, could the gravitational pull of the asteroid exert a pull on body of mars, that could have an effect on mars molten core centre, exerting heat and pressure upwards, that brings mars water liquid to the surface, then the water on mars sinks under the ground after the effect of the asteroids pull has passed.
I though of this after thinking about how the Earths moon gravitational pull effects the earth by moving water to create tides and the effects on the earths core. And how the gravitational pull of Jupiter has effected Europa's core, creating heat and pressures at the core to exert the water to the surface.
On Oct. 19, 2014, Comet Siding Spring will pass 138,000 km away from mars.
Do you think this close encounter with Comet Siding Spring would have a gravitational pull that would bring any water up from the subsurface of mars.