Scientists in the United States say they have been left speechless by the beautiful landscape revealed in detailed new pictures of the asteroid Eros.

The images have just begun to be beamed back to Earth by the space probe Near, which scientists say has provided more information than expected since going into orbit around Eros on 14 February.

The pictures reveal craters as big as some cities and boulders as tall as tower blocks. One large rock is 15 storeys high and wide, and would fit snugly inside London's Wembley stadium.

Mission scientist Mark Robinson said at a Nasa briefing: "I was kind of stunned speechless by the beauty of this asteroidal landscape. It's incredible."

Layers

The light beige peanut-shaped asteroid has a vast saddle that may have been scoured smooth as the result of a rock slide on one side of its midsection, and a crater about 3 miles (5km) across on the other.

Eros is a survivor of the Solar System's distant past. It is battered and scarred, and tells a story of great cosmic collisions from when the Earth was much younger and perhaps even before it was born.

Project scientist Andrew Cheng said the most exciting aspect of the new images was the hint of a layered structure, which suggested that Eros might have been a chip off an old planet.

He said such stratified features could occur if the asteroid was once melted while a part of a planet.

Training ground

Scientists will spend a year photographing and studying Eros - which is the size of Malta and moving through space more than 200 million kilometres from Earth.

They may then try to touch it, inching the space probe towards the giant rock to brush the surface with its solar wings and bid a final farewell.

The study of asteroids like Eros may eventually evolve into scientists using them as a training ground for human exploration.

Jet Propulsion Laboratory scientist Donald Yeomans said: "Some asteroids are far easier to land on than the Moon itself of course and they may contain water, bound up in minerals.

"So if you're going to have a human presence in space, particularly Mars, it might make sense to try out some of these technologies to turn water into usable hydrogen fuel and oxygen on asteroids."