'Pristine' Extraterrestrial Organic Compounds Found on Meteorite That Fell on Frozen Lake

On a dark winter night in 2018, hundreds of people across the Great Lakes region witnessed a radiant meteor brighten the skies. Mere days after the fireball streaked overhead on that night in January, scientists were able to track down precious pieces of the ancient space rock using weather radar reports.

The scattered remnants of the object, known as the Hamburg meteorite, contain a “high diversity” of extraterrestrial organic compounds that are preserved “in a pristine condition,” according to a study published on Tuesday in the journal Meteoritics & Planetary Science. The finding can help shed light on the origin of life on Earth, which might have been spurred in part by the delivery of organic compounds inside meteorites like Hamburg.

Though it originally measured about a half-meter across and weighed 50 kilograms (110 pounds), the meteorite broke up into small chunks that landed on the frozen surfaces of Strawberry Lake and Bass Lake in Michigan. 

The chilled environment kept the shards relatively free of earthly contamination, making them a valuable time capsule of the early solar system, said a team led by Philipp Heck, a curator at the Field Museum and associate professor at the University of Chicago.

“Because these first specimens of the meteorite were rapidly recovered from an icy surface, the time period for terrestrial alteration was short,” Heck and his colleagues said in the study. “An international consortium was formed to thoroughly characterize the meteorite while it was still fresh.” 

“The studied rock fragments show no or little signs of terrestrial weathering,” the team noted.

The Hamburg meteorite belongs to a class of space rock called H4 chondrites, which were formed in the early solar system. These relics are often filled with the same organic (carbon-containing) compounds that proved essential in the emergence of life on Earth. 

As a result, scientists think meteorites impacts may have contributed to our planet’s habitability to some degree, by seeding it with these key organic ingredients. 

“Characterizing the organic inventory of fresh, quickly recovered and properly curated falls, such as Hamburg, is useful, as such meteorites typically are less contaminated with terrestrial organics,” Heck’s team said in the study. “From each new fresh meteorite analysis, we learn more about the close mineral and organic coevolution.”

The Hamburg meteorite, for instance, contains abundant hydrocarbons, as well as sulfurized and nitrogen-containing compounds. This new sample of organic molecules from space expands our sample of materials present in the nascent solar system, and what role they may have played in triggering life on Earth.

Meteorite hunters were able to track down the Hamburg pieces by monitoring NASA’s weather radar, which captured details about the fallout of the fireball. 

“Visual observations were used to calculate an approximate trajectory, which was used to identify the signature of falling meteorites in Doppler weather radar reflections,” according to the study. “From this, a strewnfield map was prepared using weather radar data from radar reflections of falling meteorites, which guided meteorite hunters with their recovery effort.”

Heck and his colleagues hope that their successful rapid response will provide a roadmap for the swift recovery of the next precious meteorites to grace Earth’s surface, whenever and wherever they happen to fall.