"What's the point of Christensen making this outlandish statement if Head, Parker and others see morphological evidence for huge amounts of liquid water in Mars ancient past? "

Christensen is not Head, nor Parker. He has better, newer data and is making a more informed and more accurate analysis. Read my lips, Barry, "the oceans of Mars are dead". They are as accurate as Lowell's canals and Wells' Tripods.

"When Mars Express gets into Martian orbit in December, we'll just see if Christensen's dry Mars holds up okay?"

Fine, and will you shut up when the radar shows inpenetrable multi-km permafrost across the entire planet, or will you bleat for different data that supports your monomaniacal crusade for life on a barren lifeless planet?

"Do you really honestly think the Martian rampart craters, tributaries and tear drop islands are formed in a dry environment? Vast areas of Mars remain over the triple point of water during extended periods of time -- this means if there is ice, it melts, that means liquid water near the surface. It seems simple enough to understand. Occam's razor says the simplest explannation is usually the correct one. I would say water, glaciers and H2O ice meet occams razor criteria very nicely. Certainly liquid CO2 flows did not form the Martian tributaries..."

Rampart craters - ice

Tributaries - Noachian era, 3.7 BILLION years ago, & ephemeral water due to impacts (as per my own work, and that of Segura, Colaprete & Toon)

Tear Drop islands - occasional outburst "floods", perhaps due to CO2, or water, but not representative of SURFACE conditions.

If there is ice, it is frozen, and you must produce reasoned evidence for it EVER melting, without breaking the evidence of D/H enrichment and ice volume that TOTALLY rule out any significant melting for 3+ Ga.

Remember that the low-altitude & warm parts of Mars play the role of hot deserts. Over aeons, water will be driven out of those zones, not collected!