Scientists have started analyzing data and images acquired when the Messenger space probe passed within 200 kilometers of the planet Mercury last month. It was the first flyby of the solar system's inner-most planet in more than three decades. Those same investigators are anxiously awaiting a second flyby in October. VOA's Paul Sisco has more.

Tiny Mercury is often called the mysterious planet, largely because it is the closest planet to the sun. The last space probe to study the planet was Mariner 10 -- more than 30 years ago. That changed when NASA'S Messenger probe passed within 200 kilometers of the planet January 14th.

Principal investigator Sean Solomon was at the Johns Hopkins Applied Physics Laboratory for those first new pictures. He explains, "When those first images started coming on our screen and the whole science team could gather around those images and we were seeing a part of Mercury that nobody had ever seen close up, it was truly thrilling, and we were exploring a new world together, and it was just a tremendous high."

These were taken during the approach to Mercury.

"We got a lot of surprises in the data that we have acquired so far," Solomon said. Subsequent data and more than 1,200 images are revealing a dynamic planet with unique features.

"Even when we had a new look at the half of Mercury that Mariner 10 saw we could see things that we hadn't seen before," Solomon said." We were looking with a different viewing geometry, better resolution, color, and as one of my colleagues said, 'this is a whole new planet'."

That colleague is Robert Strom. He says, "I was like a kid at Christmas Eve, but unlike that kid on Christmas Eve, I'd waited 30 years for this, so I was extra excited."

Strom is the only member of the 1970s Mariner team still at it. An expert on impact craters, he says they are finding features on this once-active planet never seen before.

Solonom said, "It seems to have been a wonderful focus of activity, probably volcanic activity, certainly deformational activity, faulting." He compares this odd crater in Mercury's gigantic Caloris Basin to a spider. "We'd never seen it on Mercury. It doesn't look like anything t on the moon. It doesn't look, in detail, like anything else in the solar system."

With as many as 100 deep troughs radiating from an uplifted center, the huge basin appears stretched to the breaking point.

"So there is a nice chapter in the history of the evolution of Mercury written right there in the Caloris Basin and the spider is the key to unraveling that text," Solomon said. 

Strom adds, "The best is yet to come. What you're seeing here is just the tip of the iceberg so to speak."

Messenger next flies by Mercury in October and will settle into permanent orbit around the planet in 2011.