Bill Clark writes:

I realize that quite a bit of water has been found on Mars integrated
into the polar ice caps and under the surface in many areas. However,
I think the idea of masssive oceans of water having existed on Mars
for millions of years - enough to have caused the continent sized
canyons and other dramatic surface features - has some flaws.

Based on "continent sized canyons", I presume you're referring to
Vallis Marineris. What makes you think that it was produced by a
massive ocean of water, as opposed to tectonic forces?

Mars is such a small planet that it cannot keep more than a super thin
atmosphere. It's so thin that winds hundreds of miles an hour feel
only like slight breeze.

Enough to produce essentially global dust stroms. Enough to produce
ever-changing sand dunes.

This tepid atmosphere is constantly lost to
space because the gravity is so small.

So, when is the current atmosphere going to be gone?

If man ever colonizes Mars an
artificial atmosphere will have to be created but it will have to be
constantly replinished to replace what is lost to space.

Does the Earth lose atmosphere to space?

If free flowing surface water ever existed on Mars then it would
quickly evaporate into the atmosphere, and soon thereafter be lost to
space.

How quick is "quickly" and how soon is "soon"?

It is simply not possible for oceans of water to have existed
there for millions of years.

Reference? How long does it take to sculpt river channels?

The problem then is to explain what
could have caused the surface features, if not water. I believe it
was a subtle aspect of gravity, and I have the complete theory on my
website at http://home.austin.rr.com/whcii/

Both the Moon and Mercury have gravity. Would not this "subtle aspect
of gravity" produce similar features on those bodies?

I know many scientists will be horrified by this theory of mine, but
I believe it is at least as plausible as theirs about oceans of water.

"Horrified" isn't the right word, and what you believe isn't really
relevant.

Until solid evidence is found of huge, massive quantities of water
having existed on Mars, then my theory must be accepted as a possible
alternative.

How massive is "massive"? We already have solid evidence of polar
caps of water (and carbon dioxide). We see "splosh" craters that
are highly suggestive of subsurface permafrost becoming liquified
by the heat of impact. We see river channels. We see teardrop
shaped islands in some of those river channels, indicative of a
liquid flowing around an obstacle (like a crater).