  We apply laser light to induce the asymmetric heating of Janus colloids
adsorbed at water-oil interfaces and realize active micrometric "Marangoni
surfers". The coupling of temperature and surfactant concentration gradients
generates Marangoni stresses leading to self-propulsion. Particle velocities
span four orders of magnitude, from microns/s to cm/s, depending on laser power
and surfactant concentration. Experiments are rationalized by finite elements
simulations, defining different propulsion regimes relative to the magnitude of
the thermal and solutal Marangoni stress components.
