Australasian Science: Australia's authority on science since 1938

Meteoritic Time Capsules

By Stephen Luntz

Asteroid impacts can preserve tiny fragments of the ecosystems they destroy, creating a time capsule for us to open on an ancient world.

The heat released in an asteroid strike melts rocks, which can then reform as glass. Droplets of this glass, known as tektites, are deposited around the crater, but in larger collisions can be spread worldwide. Some even make it to space and have been found on the Moon.

The temperatures at which the glass is formed led people to assume that any organic material would be destroyed, but when PhD student Kieren Torres Howard conducted a close examination of the Darwin Glass associated with Tasmania’s 1.2 km Darwin Crater he found tiny traces of amino acids and material such as cellulose. The absence of oxygen within the glass means that whatever survived the impact has been protected against subsequent decay.

Prof Phil Bland of Curtin University was part of the team to analyse Howard’s findings in a paper published in Nature Geoscience. While the heat of the encounter might be expected to have burned away all trace of the source ecosystem, Bland says: “I was really surprised at the detail my colleagues could pull out. They were able to tell that this came from a swamp.”

The Darwin Crater was formed 800,000 years ago and the findings have provided insights into the climate conditions of the day.

“The exciting thing is that there is no reason we could come up with that would make the Darwin Crater unique,” Bland says. While the temperature at the centre of larger craters would have been even higher on impact, he anticipates that in every large meteorite strike there would “always be regions where things didn’t stay hot for that long,” allowing similar objects to form.

While the team found no sign of intact DNA, Bland says it is “not completely impossible” that ancient genes might be preserved inside meteoritic glass, adding that “it would be amazing” to make such a discovery.

Matching tektites from larger impacts to the correct site may prove a challenge, even if organic material can be found. Bland notes that Australia is strewn with tektites from a 750,000 year-old collision, the crater for which has never been found. He adds: “You can also find tektites from the K-T boundary”.