Under its frigid, dusty surface, Mars is humming. The quiet, constant drone periodically pulses with the beat of quakes rippling around the planet, but the source of this alien music remains unknown.

This Martian hum is just one in a slew of fresh mysteries and discoveries detected by NASA’s InSight lander. The work, described in a suite of five studies published today in Nature Geoscience and Nature Communications, provides a peek at the surprising activity above and below the red planet’s surface.

InSight touched down on Mars in November 2018, following a harrowing descent to a flat, featureless expanse near the planet's equator. Since then, the craft has been using an extremely sensitive seismometer and