On the roof of Canterbury Cathedral, two planetary scientists are trying to find cosmic mud. Whereas the crimson brick parapet hides the streets, buildings and timber far beneath, solely wispy clouds block the deep blue sky that extends into outer house.The roaring of a vacuum cleaner breaks the silence and researcher Dr Penny Wozniakiewicz, wearing hazmat go well with with a cumbersome vacuum backpack, fastidiously traces a gutter with the tube of the suction machine.“We’re searching for tiny microscopic spheres,” explains her colleague, Dr Matthias van Ginneken from the College of Kent, additionally clad in protecting gear. “Proper now, we’re amassing hundreds and hundreds of mud particles, and we hope there shall be a minuscule quantity that got here from house.”Many of the extraterrestrial mud that bombards Earth annually vaporises within the ambiance – some fashions recommend that 15,000 tons attain Earth’s ambiance (the equal of about 75 blue whales). However about 5,200 tons of micrometeorites fall to Earth, based mostly on an estimate from Antarctica. These particles, which most certainly come from comets and asteroids, are tiny, between 50 microns to 2 millimetres in diameter.“You must be a little bit of a detective,” says Van Ginneken. The intense heating on atmospheric entry modifications lots of the minerals and “you need to determine the character of the unique particle based mostly on the restricted data you could have”.Dr Matthias van Ginneken utilizing a backpack vacuum cleaner to assemble materials from the roof of Canterbury Cathedral. {Photograph}: Gary Hughes/ College of KentResearchers are turning to micrometeorites for clues concerning the chemistry of asteroids and meteorites. By taking a look at chemical variants often called isotopes, scientists can perceive extra concerning the mum or dad physique that the cosmic mud got here from – and what occurred to it because it entered Earth’s ambiance.Additionally, previously, cosmic mud was extra plentiful, as there have been many extra collisions between objects within the photo voltaic system when the Earth was younger. That mud is trapped in rocks, and it could level to what was taking place in our planetary neighbourhood via Earth’s historical past, and the way it has modified.Van Ginneken and Wozniakiewicz try to know how the flux of micrometeorites modifications, amongst different science questions.“If you may get an understanding as to what number of mud particles are arriving over the floor, you can also make some estimates as to how a lot materials is arriving on the Earth over time, and subsequently, doubtlessly, what contribution house mud is making to the chemistry on the Earth,” says Wozniakiewicz.“And that’s in two methods – a few of [the cosmic materials] survive on the floor, they usually can participate in floor chemistry. A few of them dissipate within the ambiance, they usually can participate in atmospheric chemistry.”Micrometeorites can seed components on to the land and seas which aren’t frequent on Earth’s floor, in addition to within the ambiance – which might affect how these methods behave.Wozniakiewicz and Van Ginneken are searching for a selected kind of extraterrestrial mud: cosmic spherols. These tiny spheres are comparatively simple to establish in contrast with different mud, due to their distinctive form, nevertheless it takes a microscope to make sure {that a} cosmic spherol didn’t come from Earth. This makes them helpful in estimating how a lot cosmic mud fell in a selected place over a given time interval.It was considered not possible to gather cosmic mud within the city setting – it was confined to pristine locations, such because the Antarctic, or in fossilised sediment. However in 2009, Norwegian jazz musician turned cosmic mud hunter Jon Larsen started combing via tons of of kilograms of city mud particles, trying to find cosmic mud. In 2017, Larsen and colleagues, together with Van Ginneken, revealed a seminal paper within the journal Geology, exhibiting that anyone with a microscope and endurance may uncover cosmic spheres.Micrometeorites let you know about thousands and thousands of objects… They let you know extra concerning the inhabitants of asteroids as a wholeDr Penny WozniakiewiczBut it’s difficult to gather micrometeorites for scientific research, though they repeatedly fall on the Earth’s floor. The particles are simply contaminated, which may compromise their use in analysis. (However that’s not why Van Ginneken and Wozniakiewicz seem like white-clad aliens – they’re defending themselves from chicken flu, probably contained within the droppings and chicken bones we see on the roof.)Larsen “began the entire period of city micrometeorites”, says Van Ginneken. “Since then, increasingly individuals have been doing this as a pastime. A part of what Penny and I wish to do is deliver the science into it.”Cathedral roofs, comparable to Canterbury’s, are perfect for cosmic mud looking, as they’re giant, inaccessible and largely untouched. We enter via a often barred wood door, behind the cathedral’s fundamental Trinity Chapel, up tons of of tightly winding steps, after which via one other specifically unlocked door to succeed in one of many cathedral’s roofs. This was Van Ginneken and Wozniakiewicz’s remaining roof of the day – that they had trekked as much as a number of different roofs on the cathedral. They’ve additionally collected mud from Rochester Cathedral, and hope so as to add Salisbury and Winchester to their listing.Van Ginneken is eager to pattern many roofs, to know the biases that creep into city micrometeorite collections, such because the impact of rainwater. The benefit of roofs is that they’re simply accessible, he says. Going to Antarctica, the place numerous micrometeorite analysis has been undertaken, “may be very costly, it takes numerous preparation, and there’s a restrict on the quantity of samples you possibly can deliver again”. Additionally, the analysis is restricted to a selected local weather and latitude. Roofs broaden the alternatives to research how these tiny mud particles work together in several environments.One among Dr Matthias van Ginneken’s scans of a micrometeorite. {Photograph}: Matthias van GinnekenThe abundance of city micrometeorites additionally opens up planetary science to those that don’t essentially have entry to the haul from bigger house missions. And there may be growing curiosity within the bounties of outer house. Nasa’s OSIRIS-REx mission, for instance, final yr introduced again to Earth materials from the asteroid Bennu, which is greater than 4.5bn years outdated.“These missions are nice,” says Wozniakiewicz. “They go to a single object, they usually inform you a large number about that one object. Micrometeorites let you know about hundreds, thousands and thousands of objects… They let you know extra concerning the inhabitants of asteroids as an entire, a snapshot of all of the totally different processes, all of the totally different our bodies which can be on the market. After which you possibly can evaluate these samples, together with meteorites, to the samples which can be being introduced again from these missions.”Cosmic mud may additionally maintain clues to our personal planet within the distant previous, says Dr Martin Suttle, a lecturer in planetary science at The Open College. It may have additionally created a hospitable setting on early Earth that allowed life to spark spontaneously, in response to a brand new paper revealed by Suttle and colleagues in Nature Astronomy.“There was extra mud coming to Earth, perhaps 1,000 instances extra mud, than right now,” he says. “That mud carries plenty of stuff which is engaging as a feedstock for early prebiotic chemistry, issues like iron steel, which is in any other case not current on the Earth’s floor.”However amassing the cosmic mud is simply the start of the analysis course of, and arguably the simpler half – regardless of all the cathedral’s stairs. The luggage of mud will now be sterilised in order that they’re protected to work with, after which the scientists will study every particle underneath a sterile microscope.“We’ll spend hours and hours and hours and hours simply extracting spheres and hoping that one is a cosmic spherol,” says Van Ginneken.