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What the dust of space tells us about ourselves

Every year, roughly 10 space dust particles land on every square meter of the Earth’s surface. “It means they’re everywhere. They are in the streets. They are with you. You may even have cosmic dust on your clothes, ”said Matthew genge, a planetary scientist at Imperial College London who specializes in these extraterrestrial dust grains, known as micrometeorites.

Round and multicolored like tiny marbles, micrometeorites are as distinctive as they are ubiquitous, but they escaped attention until the 1870s, when HMS Challenger expedition dredged some from the bottom of the Pacific Ocean. (On earth, the accumulation of earth dust tends to overwhelm and conceal the cosmic type.)

For a century, scientists thought that the strange spherules found on the seabed sank molten surfaces of larger meteors as they crashed into the atmosphere. In fact, cosmic dust floats here from space rocks hundreds of millions of miles away, carrying tiny messages.

For 30 years, Genge has been deciphering these messages, one grain at a time.

He began his career just as Antarctica was identified as an abundant new source of micrometeorites. Strong southerly winds help sweep away land debris, so up to 10% of the dust deposited in the ice comes from space. “I have to do a lot of easy things,” Genge said, like figuring out “what they’re made of, what they look like, what the different types are.” Since then, he and other micrometeorite specialists – a community small enough that he “knows most of the children of them” – have gleaned much more information from the dust. Recently, Genge has interpreted the messages conveyed by space dust, not about its origins, but about its destination: Earth at different times in the history of the planet.

Genge collected this dust from a moraine in Antarctica in 2006.Photography: Harry Genge / Quanta Magazine

The bald, stiff Briton takes Zoom’s calls in his London bedroom, trapped between a bed, cupboard and microscope. He brought the microscope home from the lab as the lockdown was about to begin last March, with a lot of dust. When we video chatted this winter, Genge grabbed a plastic jar from a cabinet box and shook it in front of the camera. The jar was half full of tawny silt – Antarctic dust, part of Earth, another alien. Sorting it out, Genge could possibly stumble upon a speck of 6626 Mattgenge, an 8-kilometer-wide asteroid near Mars named in his honor for his contributions to the study of cosmic dust.

Our conversation about his dusty findings has been condensed and edited for clarity.

Have you always liked meteorites? How did you get interested in geology?

As a child I was fascinated by Arthur C. Clarke’s mystery books. This is what led me to ask a lot of questions. But the reason I was drawn to geology was that I loved art. There were two courses in which I was able to do a lot of drawing: one was geology and the other was art. And as soon as I went out into the field and started drawing rocks and realized that I could use my drawings as detective stories, to work out the formation of this rock, to see events that take place. were produced millions of years ago, I was hooked. Then I was geology until the end. [Genge is the author of Geological Field Sketches and Illustrations: A Practical Guide, published in 2020.]

Sketches help geologists interpret rocks and meteorites. Genge’s notebook includes slices of metamorphic rock (left) and pahoehoe (right) – a lava flow with a smooth, folding surface (right).Photography: Harry Genge / Quanta Magazine

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