New Delhi: In a first, scientists have found souvenirs left by space on the rooftops of buildings in Paris, Oslo and Berlin!
Yes! Traces of cosmic dust have been discovered in urban environments and research has shown that these micrometeorites are still falling on Earth billions of years later.
Cosmic dust is a term for small amounts of matter in space, including those left over from the formation of our solar system some 4.6 billion years ago.
"We've known since the 1940s that cosmic dust falls continuously through our atmosphere," says planetary scientist Matthew Genge from Imperial College London in the UK.
"But until now we've thought that it could not be detected among the millions of terrestrial dust particles, except in the most dust-free environments such as the Antarctic or deep oceans," Science Alert reported.
Attempts were made earlier to identify cosmic dust in cities, but research only turned up with industrial pollution-induced terrestrial grime and particles.
Now, however, 500 particles of cosmic dust were found, after Genge and his fellow researcher Jon Larsen investigated 300 kilograms of sediment collected by roof gutters in the three European cities.
As per Science Alert, cosmic dust grains contain magnetic minerals, so the team was able to extract them from the rest of the sediment using magnets, and identified them on the basis of their composition.
The grains they found are what's called silicate-dominated (S type) cosmic spherules, which are melted into non-spherical shapes due to the intense heat they encounter during entry into Earth's atmosphere.
Measuring 0.03 millimetres, the newly-found particles are slightly larger than what they normally are, that is 0.01 millimetres.
They also contain subtle crystal variations in their structure, which resemble samples dating from medieval times, which is disfferent from the ones dating back millions of years found in Antarctica, which feature a different crystal composition.
These distinct differences are being attributed to minor changes in the orbits of planets in the Solar System, while scientists are still trying to put a finger on the exact reason.
Over millions of years, the way planets move around the Sun varies slightly due to gravitational variations, and this in turn affects the gravity exerted by each planet on the matter around it.
Based on the size and shape of the particles, Genge thinks they were melted as they plummeted to Earth at speeds of around 12 kilometres per second (7.5 miles per second), which would make them the fastest-moving dust particles found on Earth.
The researchers also suggest these could be the youngest cosmic dust particles ever discovered, estimating that they fell to Earth within the past six years, the report in Science Alert said.