Cosmic dust flux variation measured on the ocean floor!

These micrometric dust particles, which are less spectacular than meteorite falls, nevertheless represent an average of 40,000 tonnes per year of matter entering the atmosphere. Changes in this flow of particles could therefore have an impact on variations in the Earth’s climate.

As this dust settles to the bottom of the oceans, boreholes can be drilled to trace the history of cosmic bombardment of the Earth. To differentiate between these extraterrestrial dusts in the sediments, the authors of the study developed an analysis technique that uses the difference in abundance of helium (3He and 4He) and neon (20Ne, 21Ne and 22Ne) isotopes compared with terrestrial abundances to identify the composition of cosmic particles.

In the end, the geochemical signature obtained turns out to be essentially that of the solar wind, which becomes embedded in the particles as they travel interplanetary. And the study of the ocean cores highlights two major variations in this cosmic flux over time, 35 and 8.2 million years ago.

To find out more :

• D. Chavrit, M.A. Moreira and F. Moynier (2016) Estimation of the extraterrestrial 3He and 20Ne fluxes on Earth from He and Ne systematics in marine sediments. Earth and Planetary Science Letters 436, 10-18, doi:10.1016/j.epsl.2015.12.030
• Presentation of the article on the Labex Univearths website