"It's completely unexpected," chief investigator Donald Brownlee of the University of Washington, Seattle, told reporters.

"We were expecting the surface to look more like it was covered with pulverized charcoal ... like a dirty, black, fluffy snowball.

"Instead," he said, "it was mind-boggling to see the diverse landscape in the first pictures from Stardust, including spires, pits and craters, which must be supported by a cohesive surface. "We know Wild 2 has features sculpted by many processes," said Brownlee. "It may turn out to be typical of other comets, but it is unlike any other type of solar system body."

"Another big surprise," said Benton Clark, with Lockheed Martin Space Systems of Denver, "was the abundance and behavior of jets of particles shooting up from the comet's surface.

"We expected a couple of jets, but saw more than two dozen in the brief flyby," he said.

Stardust crossed paths with the comet in January and shot 72 high-definition images of its nucleus.

SPACE.WIRE