Meteorite Holds Possible Clues to Life's Origins

Sept. 8, 2000 -- On Jan. 18, a 400,000-pound rock streaked through the sky and slammed into a remote lake in Canada.

Although no one actually saw the meteorite strike Earth, many were startled by the booming sound it made as it exploded in the atmosphere and by the brilliant, multicolored streak it left behind in the clear morning sky.

Data released by secret U.S. Department of Defense satellites is helping Canadian University researchers retrace the path of this extremely rare organic asteroid. Their research may also help reveal clues about the origins of life.

“It’s as though we went out in space on a sampling mission and got a bit of material and brought it back,”said Peter Brown, a meteor scientist in the Department of Physics and Astronomy at the University of Western Ontario. “That is extremely valuable scientifically.”

Brown is co-leader of a research team that’s focused on learning from the largest, most important meteorite find in Canadian history. The meteorite struck Tagish Lake in northern British Columbia and scattered in the form of 500 charcoal-like chunks.

Cobbling Images

Local resident, Jim Brook, happened upon the find that was strewn for 4 miles on the lake’s ice. Other witnesses supplied images taken after the impact. The dust trail it left behind hung in the atmosphere long enough for two dozen residents to capture it in photographs and on videotape.

Traditionally, scientists have used such pictures and eyewitness accounts to try and determine the size, velocity and trajectory of meteors and asteroids. The Tagish find marks the first time the DOD has released data for use in calculating the orbit of a recovered meteorite.

Of the 20,000 meteorites ever found, an orbit has been established for only four.

More significantly, the tagish Meteorite also marks the first time there has been enough data to calculate the orbit of a carbonaceous chondrite, an extremely rare, organic meteorite that may be linked to the origins of life.

Using the available DOD data from optical and infrared sensors, Brown estimates the meteorite sped to Earth at about 10 miles per second — about 20 times the speed of a bullet.

To calculate the trajectory from the ground, Brown took the three best sets of photographs showing the fireball’s dust trail. Then, using images in the foreground, he positioned his own camera to within an inch of the original.

With his camera in place, Brown took a series of photos of the night sky to provide a star field that could be digitally superimposed over the original photos. The star field provides an accurate way of measuring the altitude and angle of the meteorite’s descent.

The military satellite grid also collected visual data, which Brown describes as being similar to a photograph. That data is now being used to cross check the calculations made from the public photographs.

“There’s a synergy, here. You’re fusing data from two different sources,” Brown said. “They are completely independent solutions using two different sensors separated by thousands of kilometers.”

Seeing ‘Everything, Everywhere’

While the DOD has been generous in sharing data on the meteorite, it won’t discuss the number, position or purpose of the military satellites that recorded the information.

“Put it this way, we look everywhere and we’re always looking,” said Ed Tagliaferri, a physicist and consultant to the U.S. aerospace program who reviewed the DOD data to determine exactly what could be declassified.

Tagliaferri says it’s not uncommon for the military satellite grid to track foreign bodies colliding with the atmosphere, but the Jan. 18 impact was unique since it was the largest ever recorded over land by the satellite systems.

It’s estimated the 400,000-pound meteorite was 15 feet across before it detonated in the atmosphere with a force of two to three thousand tons of TNT. Two massive explosions could be heard across parts of northern British Columbia, the Yukon and Alaska.

Despite the size of the explosion, the 10-mile-per-second collision with the atmosphere was relatively slow as meteorite impacts go. Meteorites have been clocked entering the atmosphere at speeds of up to 46 miles a second.

Brown is now hoping to refine the satellite data to calculate the meteorite’s velocity within 650 to 1,000 feet per second. If he can do this, he says he might be able to identify just which family of asteroids, within the Asteroid Belt, it came from.

Piece of Cosmic Puzzle

Asteroid families are thought to be fragmented pieces of what were once larger celestial objects. They are generally clumped together in close orbit and are composed of the same type of material.

“If we can definitively link this meteorite with a certain class of those objects then that would be one more piece of the larger cosmic puzzle,” Brown said. “We will be able to say, for example, this certain group of asteroids is organically rich without having ever gone there.”

A large part of that puzzle centers on if carbonaceous chondrite meteorites, like those found melted into the surface of Tagish Lake, played a role in seeding our planet with life.

In 1996 NASA scientists announced they had found possible fossilized evidence of life in a different kind of carbonaceous chondrite, called ALH 84001. But analyses of this Mars rock are still under dispute.

The Tagish Lake meteorite may yield even more intriguing information.

Accounting for only 0.1 percent of meteorites recovered to date, the Tagish Lake find is a Carbonaceous Ivana (CI), the rarest subclass of carbonaceous chondrite meteorites. CIs represent the most primitive samples known from the early solar system and include building blocks for biological material that could have seeded life on Earth.

“This is, by no means a typical chondrite,” Brown says, “and I expect there will be many new finds that come out of the analysis.”