264 kilometres per second — that's how fast the Solar System hurtles through the cloud of dark matter. Its existence was given away by galaxies: they spun too fast to be held by visible mass, and Vera Rubin was first to suspect a hidden scaffolding.

But here's the rub: a neutrino downpour also pelts the detectors. Coherent neutrino scattering mimics the WIMP signal to a tee, devaluing years of effort. The way out? Learn to discern direction. If dark matter is a wind, then the detector must become a compass, showing where it blows from.

Just such a compass was built at the Modane underground laboratory. The MIMAC detector is a microscopic time projection chamber, filled with a mix of isobutane and CHF₃ at 30 mbar pressure. Low pressure stretches recoil nuclei tracks to several millimetres, allowing their shape to be reconstructed in three dimensions. Tracks are read by a pixelated anode; digital processing reveals head–tail asymmetry, indicating arrival direction. The cosmic ray background is weakened by the mountain overburden, and electronic tracks are suppressed one hundred thousandfold by a Machine Learning algorithm. Remaining events are projected onto a galactic map. The ON/OFF method compares signal in a 15° cone around Cygnus with thirty random sky patches.

Joint analysis of two chambers over an effective 0,02 kg·days found no excess. The upper limit on the spin-dependent WIMP–proton cross section is 6,65×10⁻³⁶ cm² at 90% confidence. Bootstrap accounted for uncertainty in control region placement.

This result changes the game. A compact gas detector with no multi-tonne passive shielding has shown sensitivity comparable to the giants. Directional detection is the only way to punch through the neutrino noise and reach light dark matter particles. Next step: the MIMAC-35cm detector with 12 times the volume. It won't just point the way like a compass — it will become a navigator, able to chart the invisible wind from Cygnus.