Ethiopian Review

A huge iron-nickel meteorite discovered on the surface of Mars by one of NASA’s robotic geology stations is giving scientists unexpected insights into the planet’s past.

Among the questions scientists are scrambling to answer is how the watermelon-sized metallic rock managed to make it to surface of Mars intact.

Computer models show that the planet’s current atmosphere could cushion the descent of a meteorite only about one-tenth the size of the meteorite the rover Opportunity spotted late last month.

Anything larger would have been mostly or totally obliterated on impact, leaving only a crater.

“The fact that this meteorite is still intact tells you that the atmosphere must have been denser to slow it down for the fall,” planetary geologist Matt Golombek, with NASA’s Jet Propulsion Laboratory in Pasadena, Calif., told Discovery News.

Opportunity has been exploring an equatorial region of the planet known as Meridian Planum since January 2004 looking of signs of past water. It discovered a much smaller metallic meteorite in December 2004 as it was probing part of its discarded heat shield.

Scientists have no way to determine when the meteorites arrived, but they know neither had much exposure to water. On water-rich Earth, iron meteorite, such as the kind discovered on Mars, quickly rust.

The newly discovered meteorite, nicknamed “Block Island” has markings that look like it has been etched with acid, said rover science team member Ralf Gellert, with the University of Guelph in Ontario, Canada.

“That’s possibly a clue as to what’s happened,” Gellert told Discovery News. “It tells you something about the environment that was there billions of years ago.”

The rover had been on its way to its next target, Endeavour Crater, when it drove past a black rock in late July.

Because most rocks in the area are light-colored, the rock stood out even in the black-and-white images from the rover’s navigation camera.

So, for the first time since arriving at Mars 5.5 years ago, Opportunity was turned around so it could drive back for closer inspections. Scientists discovered it was a very common metallic meteorite that is 93 percent iron and 7 percent nickel.

“It’s pretty standard. We have bazillions of those in our collections on Earth,” Golombek said.

Because scientists are so familiar with this type of object, studying how it appears different on Mars is expected to yield new insights into the planet’s environment.

“This is a really good object to investigate because you know what it looks like,” Gellert said. “It’s like an experiment where nature has given us a known object on the surface of Mars and we can measure all the changes.”

Opportunity is scheduled to spend about another week at the meteorite, probing spots and other features on its surface.

“This is a rare find and obviously want to learn anything about it before you push on,” Golombek said.

- By Irene Klotz | Discovery News