Hunting for meteorites may sound like a cool way to spend an afternoon, but imagine doing it from an airship.
A couple weeks after a meteorite blazed to Earth April 22 over California’s Sierra Nevada mountains, a team of researchers flew aboard the commercial airship Eureka to try to search for pieces of the space rock.
The 10-foot hunk of rock, about the size of a car, burned to pieces in the air above Sutter’s Mill, the site where gold was first found in California. A thunderous boom announced its arrival, and scientists raced up to the site to look for pieces of the meteorite. They only found disappointingly small pieces, but it was enough to determine the meteorite was a rare, carbon-containing type. Studying it could help scientists learn how the building blocks for life – like carbon, nitrogen and oxygen – ended up on Earth.
The meteorite's fall ranged over about 20 miles, so the best bet for finding more pieces was to look for scars in the landscape from the air.
"An airship is perfect, because it flies at 1,000 feet and it moves very gradually, very relaxed," said astronomer Peter Jenniskens at SETI Institute and NASA Ames Research Center, who led the airship search party.
They flew in a German-built Zeppelin-NT, owned and operated by the company Airship Ventures and housed in one of NASA's giant hangars at Moffett Field in California, the same airfield where the airship USS Macon (ZRS-5) was once based. At 246 feet, the Eureka is longer than a Boeing 747 airplane. While its usual job is giving tourists aerial views of the Bay Area, it has been used for a number of scientific missions, including the meteorite hunt.
Unlike a blimp, an airship has a rigid frame. Eureka's frame is made of aluminum and carbon fiber and encased in a tough fabric envelope made by the same company that makes fabric for NASA's spacesuits. If you were to shoot a bullet into it, it would deflate very slowly because the air is at low pressure. Its three 200-horsepower engines power propellers that maneuver the giant airship around like a helicopter.
Jenniskens and his team used a camera aboard the airship to look for signs of meteorite wreckage. They pinpointed 12 sites to inspect more closely from the ground, but none contained any big chunks of meteorite. Instead, any black fragments at the sites turned out to be charcoal, and one "really interesting hole in the ground" turned out to be a sinkhole, Jenniskens said.
While the zeppelin hunt didn’t immediately turn up large bits of the Sutter’s Hill meteorite, the search continues on the ground. The largest piece of meteorite found so far weighs about half a pound – less than a can of soda. Jenniskens will be going out again throughout the summer, before the fall rains degrade the fragments.
Scientists around the world will be analyzing these fragments to understand the meteorite’s composition and origin. "These meteorites are basically a window on our past, when the planets were forming," Jenniskens said.