It was in at least 200 of those images that scientists announced Thursday that they had spied gullies apparently formed by the comparatively recent flow of torrents of water, soil and rocks spilling down the walls of craters pocking Mars.

A flood of similar images continues to pour in from the Global Surveyor and will do so until the mission ends in February 2001, although it could well win a one-year extension.

The continued coverage will allow the satellites eagle eye to image many gully features on a repeated basis, tracking any present-day activity.

"If we see one that changes, wow, well be back," promised Ken Edgett, staff scientist at Malin Space Systems.

The discovery of sources of liquid water neatly dovetails with NASAs ambitious strategy to explore Mars, the planet that most closely resembles our own.

"We feel vindicated," said Jim Garvin, NASAs Mars program scientist.

"Follow the water," has been the agencys Martian mantra of late: Where it flowed, when and where it might have gone. NASA lost two missions the Mars Polar Lander and the Climate Orbiter last year that were to have contributed to that quest. Later this year, NASA will sketch out a 20-year plan that reprises the theme.

"For once, we seem to be on the right track," said Richard Zurek, the project scientist on the two ill-fated missions who is now at work on a proposed orbiter to be launched in 2003.

Although water on Mars is nothing new tons of the stuff is locked up in the planets poles and atmosphere it is the suggestion that it exists in a liquid form so close to the planets surface that jazzes scientists.

"Were seeing the potential of that water being more accessible to our robotic tools than ever before," Garvin said.

The vast quantities of water at one point, Malin spoke of a feature that required the outpouring of as much as 66 million gallons (250 million liters) of water to form further buoy the prospects that Mars may harbor life.

The water could also support human life on future missions to the planet. Once on Mars, astronauts could use the water for drinking, air to breathe and fuel for the return trip home.

"Before we send humans to Mars, there is a lot of homework we have to do," cautioned Edward Weiler, NASAs associate administrator for space science.

NASA will pick up the thread again in April 2001, with the launch of another orbiter to Mars.

Mars Surveyor 2001 Orbiter

The Mars Surveyor 2001 Orbiter will carry a suite of science instruments. They will be able to map the mineralogy, morphology and elemental composition of the Martian surface, as well as determine the abundance of hydrogen and thus water, frozen or liquid in the top few feet (meters) of the soil.

Although the resolution of some the instruments precludes the targeting of the narrow features announced on Thursday, they will allow the global mapping of minerals that are characteristic of the interaction of water and rock, said R. Stephen Saunders, the 2001 missions chief scientist.

"Well be able to nail down at last what the water left behind," Saunders said.

Whether it is truly water behind the features remains to be seen.

"This story, I don't believe, will be answered until someone goes to one of these cliffs with a pick and shovel and digs into it," Malin said.

Actually accessing those materials sloughed off by the landslides is the multimillion-dollar question, however.

The earliest NASA will return to the surface of Mars a place it has not successfully landed a spacecraft since 1997 is 2003. The agency is a month away from deciding whether to send an orbiter or a lander or neither during that launch opportunity, Weiler said Thursday.

While an orbiter could continue the high-resolution reconnaissance work begun by the Global Surveyor, a large rover carried to the surface aboard a lander could roam far afield, collecting and analyzing samples.

"Id buy stock in the rover, I guess," Saunders joked.

Athena Mars Rover

But if Athena -- the rover being readied -- is called up for Martian duty in 2003, it probably could not reach the seeping crater walls and floors imaged by the Global Surveyor, scientists associated with the project said.

"This is a very exciting result, but we have to have realistic expectations," said Steven Squyres, a Cornell University astronomy professor and the Athena rovers principal investigator. "I dont think in 2003 youre going to see a rover neatly deposited at the bottom of these things, climb up and pound a pipe into the rock."

The problem, said Ray Arvidson, a Washington University geologist and Athenas deputy principal investigator, is that NASA does not have the technical ability to land a spacecraft close enough to such a small feature that a roaming rover could travel the remaining distance to it.

"It may be we need a couple of years to design a mission -- a scout or small lander -- that can target these areas and penetrate them vertically," Arvidson said.