From Earth Dust to Space Dust

Antarctic cosmic dust (spherules, micrometeorites, etc.) found by Lauren (scale bar 1 mm)

All week we have been riding our snow machines in a line – aka doing sweeps – over the blue ice and finding 20 or so meteorites a day. Johnny is predicting that we have about two days left of sweeps to finish a major blue ice area of Davis Ward that we call the “Big Tongue”. Since we have only about a week left in the field, today we did some prospecting to help get ready for next season. We rode our snow machines to a new location to see if there were meteorites and to collect some samples.
As we rode our snow machines today, I caught myself being a bit nostalgic; the areas we rode by reminded me of the work I did for my masters thesis. I studied tiny cosmic dust particles that were in sediment collected from the tops of Antarctic mountain peaks. I examined the sediment under a microscope to hunt for glassy particles, knocked off of Earth by a meteor impact, called microtektites. About 790,000 years ago there was an asteroid impact somewhere in Southeast Asia, which melted a part of the Earth’s crust. This molten debris got flung halfway around the world – all the way to Antarctica! It has been a mysterious event as the debris was widely distributed but scientists had yet to identify where the crater was located… until possibly now. There is a recent paper out that may have identified the crater location but unfortunately internet is a luxury we’re living without. I’m looking forward to reading it once we get back to civilization.
While I was hunting for microtektites (from Earth) to study, I found thousands of micrometeorites (from space) as well. So as we drove by patches of sediment today I couldn’t help but wonder just HOW many thousands of micrometeorites we were passing by. I know a sure fire way to boost our meteorite count this season! But in all seriousness, with only a week left in the field, we’re crossing our fingers the weather holds and the sweeps continue to be profitable. And I’ll continue to be thankful for the opportunity to pay it forward by collecting Antarctic samples for other scientists to study.

-Posted by Lauren, coming full circle with her thesis

 

Note from RPH:  The paper Lauren mentions is Sieh et al (2020) Australasian impact crater buried under the Bolaven volcanic field, Southern Laos and can be found at www.pnas.org/cgi/doi/10.1073/pnas.1904368116.  The source crater for the Australasian tektites has been sought and not found for the better part of a century, sometimes accompanied by Indiana Jones levels of secrecy, intrigue and misdirection. While the claim in the Sieh et al paper is not absolutely bulletproof,  it is the best candidate I’ve seen in four decades of paying attention, with just enough signs of impact deformation and good ages. The crater has gotta be somewhere in the region! Here’s hoping this new paper generates a well-funded, detailed follow-up study with core drilling; find an impact melt sheet of the right chemistry and age and everyone will believe.