Rasmus is a permanent academic member of staff, with expertise in isotope- & trace element geochemistry; and mass spectrometry, and is responsible for the isotope and trace element laboratory at Institut for Geoscience. He earned his Ph.D. from Dartmouth College (Hanover, New Hampshire, USA) in 2007.

After earning his Ph.D., Rasmus was employed as a postdoctoral researcher in the Department of Earth Science & Engineering, Imperial College London, England, and held an adjunct position at the Natural History Museum, London (2007—2011).

Therafter, Rasmus worked as a research assistant professor in the Department of Earth and Atmospheric Sciences, University of Houston, Texas, USA, and held an affiliation as a visiting scientist at NASA—Johnson Space Center (2011-2015), before taking up his current post at Aarhus Universitet.

Since his return to Denmark, Rasmus' research has been supported by grants from Danmarks Frie Forskningsfond (DFF), Aarhus Universitets Forskningsfond (AUFF-NOVA), and Torben og Alice Frimodts Fond.

He serves as tillidsrepræsentant for staff hired on academic contracts at the Institut for Geoscience, and as the chairman for PIGA, the institute's staff association.