Phil's earlier comment is important:

>I no longer think the warm wet early Mars is a valid paradigm.
>Always had trouble with the fact that the early Sun was
>about 65% today's luminosity back when Mars was supposedly
>warm and wet. Mars shoulda been REALLY cold.

Because the Sun is a main sequence star, we know it was less luminous
when it was younger. The Sun's luminosity has grown as it grew
older. If Venus, Earth and Mars had no atmospheres then their surface temperatures would have been less with the early Sun. However the three worlds do have atmospheres. Atmospheres enable Green House effects provided the atmosphere has green house gases, e.g. carbon dioxide, methane and water vapor. The Green House effect increases surface temperature. If the planet has liquid water on its surface then increased temperature will cause cloud formation. Clouds will reflect sun light back into space. Less light means less surface temperature which causes the clouds to rain out and go away. This is a well known "closed loop feedback process" that regulates a planet's surface temperature. If sufficient light is entering into an atmosphere such that all of the surface water evaporates then the protective feedback process breaks down. This leads to a "runaway greenhouse effect". Venus originally had oceans and a fully functioning protective greenhouse effect. As the Sun's luminosity increased, the oceans of Venus completely evaporated. A runaway greenhouse effect took place and the water vapor was transformed into sulfuric acid. We know from the Earth's example that biological genesis occurred almost immediately after the Earth's surface cooled. It is reasonable to assume that the same occurred on Venus and that life continued there until the atmosphere went into a full run away greenhouse effect. Why hasn't the Earth died like Venus? Answer: Give it time. It is widely believed that a greenhouse effect will eventually kill the Earth in about a billion years. The Earth has survived up until now because most of the Earth's early atmosphere has been incorporated into the Earth's crust and mantle. The Earth's coal fields, limestone and dolomite are composed of carbon and carbon dioxide from the ancient atmosphere. Now employ this analysis on Mars. The Martian atmosphere has never been thick enough to support a significant green house effect. The "warm and wet theory" is now broken (too much olivine laying about on the Martian surface). Mars has never been warmer than it is right now. The surface temperature and pressure of Mars is too low to support life.

Mars is almost certainly dead and probably never had life on it.

Lots of people know about the early Sun argument. Lots of people also know about the methane marker argument, e.g. a planet can not be supporting life if there is no measureable methane in the atmosphere. In situ measurements by the Viking landers in 1976 showed no measureable methane in the Martian atmosphere. Clever people run NASA. Clever people know these arguments.

The following is NOT an interesting question:

Is there life on Mars?

The following IS an interesting question:

Why is NASA selling the Mars program based upon the assumption that there is life on Mars?

The results of MER are going to force many people to start asking the "interesting question".

Gary