Earth as seen by the Apollo 11 astronauts floating above the moon NASA
A mysterious layer of space dust that coated Earth millions of years ago could be shrapnel from asteroids that smashed into the moon, according to a new analysis of soil from below the sea floor.
In the 1990s, geologists found unusually raised levels of helium-3 across Earth’s crust, dating back to around 33 million years ago. This was puzzling because the isotope almost always appears only in objects from space, as a result of bombardment by cosmic rays.
![Small dome in the Compton-Belkovich region (61.33 ?N, 99.68 ?E). Evidence indicates a volcanic origin for this and other intriguing features in the region. Incidence angle is 64?, Sun is from the SSW, image is ~510 m across. NAC image number M139238146L [NASA/GSFC/Arizona State University].](https://images.newscientistbeta.com/wp-content/uploads/2023/07/07172644/SEI_163208069.jpg)
