Willeke Mulder is a PhD student in the field of Astronomy and Astronomical Instrumentation, working at the Leiden Observatory in the Netherlands. She is trying to identify and characterize bio-signatures of life on Earth to create a model of the Earth as if it were an exoplanet. One of the first steps is measuring the spectropolarimetric response of several surfaces. She focuses on the linear and circular spectropolarimetric signals of the Earth at visible wavelengths, and their temporal variability.