The U.S. Spirit spacecraft has sent its first color postcard from Mars. It is the sharpest image ever taken of Mars or any other planet.

The image from the color panoramic camera mounted on the Spirit rover shows in far greater resolution the rock-covered view first transmitted by a low resolution black and white camera on Monday.

"This is it. This is the day we've been waiting for," said Cornell University scientist Jim Bell, who led the camera's development, says it reveals details of rocks of a variety of shapes and sizes. "My reaction has been one of shock and awe! You have to understand, we designed it to do this, so we shouldn't be surprised, but, boy, it's spectacular looking at the details."

The fine detail of the rocks and Martian surface will help investigators decide where to send the rover next week to search for signs of water they believe once flowed in this ancient crater.

Even better, three-dimensional images are yet to come. They will allow researchers to judge rock sizes and distances more accurately.

The scientists say this picture shows angular rocks whose edges have been rounded - a sign that wind-blown dust sandblasted them over the eons. Jim Bell says it means mean less work for the rover's scraping tool, which was designed to remove the weathered exterior of rocks to expose their true composition. "Some of these things, except where they have been coated with dust, may be very, very clean and we may not have to struggle very hard to get a look at the nature of these rocks at all because I think Mars may have cleaned them off for us," he says.

The scientists point out that the color picture reveals a strange new type of Martian soil with unusual textures. They describe it as a material they call "duracrust" because it held together and even folded over itself when the spacecraft's cushioning airbags dragged it as they retracted.

Mr. Bell speculates that salts left over when water percolated up from the ground are the cement that holds the dirt together. "We're trying to figure out for the physical properties of this material. I think trenching into this stuff is going to be an absolute blast [fun] once we get the rover down on to the surface," he says.

Engineers at the Jet Propulsion Laboratory in California took a step to prepare for moving the rover off the lander next week. They remotely set off explosive charges that released a blade to cut through the second of three restraining cables.

They are trying to solve a minor heat problem with the rover. Although Mars is extremely frigid at about minus 85 degrees Celsius, it is warmer than expected and the rover is getting warmer than planned. To avoid overheating its circuits, they are letting rest more and having it communicate less.

In Washington, President Bush called the mission team in California to congratulate it for its success. A White House spokesman says Mr. Bush suggested that their work helped heal wounds from the space shuttle Columbia disaster.