Cosmic dust isn’t all mystical fairies and unicorns, but it does have secrets—and this cosmic dust is telling us secrets from 98 million years go.
You may not realize it, but tons of micrometeorites swirl down to Earth every day. Scientists have been finding their fossils embedded in rocks for several years. Micrometeorites swirling to the surface now are the debris of events that are much more recent (at least on a cosmic scale).
Now a research team who obtained rock samples from England’s cliffs of Dover have unearthed space dust so old that that figuring out how much fell to the surface at a particular point in time could reveal turbulence at the dawn of the solar system, such as asteroids smashing into our planet and comets whizzing dangerously close. Comet tails are obviously going to generate massive dust clouds. So is head-butting an asteroid.
“The iconic white cliffs of Dover are an important source of fossilized creatures that help us to determine the changes and upheavals the planet has undergone many millions of years ago,” said Martin Suttle, who recently published the study in Earth and Planetary Letters with co-author Matt Genge. “It is so exciting because we’ve now discovered that fossilized space dust is entombed alongside these creatures, which can also provide us with information about what was happening in our solar system at the time.”
Suttle and Genge believe that the prehistoric dust could shed light on what was happening to Earth during a period for which we have hardly any cosmic dust evidence. Particles of debris may have been previously overlooked because the fossilization process of Earth rocks can obscure their identity. Micrometeorite fossils surfaced more easily in the Dover study because the team developed a new method of exposing dust embedded in the rock.
Micrometeorites can be identified by their spherical structure and crystals that look like micro-Christmas trees. The tiny spherules the team found, whose chemical composition varied from silicate to iron-type micrometeorites to recrystallized magnetite, were observed with an electron microscope and then went through a process that would make their insides visible in HD.
“This study demonstrates that fossil, pseudomorphic micrometeorites can be recognized and are likely common within the geological record,” the team said.
Anywhere from 5 to a staggering 330 tons of cosmic dust may swirl through our atmosphere every day, at least as estimated by satellite observations and other data. Where it comes from depends on what phenomena have occurred. While comets do leave behind immense amounts of dust, these particles stream by so fast that most never see the surface. Asteroid dust from the Kuiper belt can take a million years to reach Earth.
For Suttle and Genge, it seems what they unearthed was definitely worth the 98-million-year wait.