On Mars, as on Earth, the air breathes: pressure rises and falls in rhythm with the daily tide — a wave heated by the Sun. But hidden in the InSight recordings was another, weaker wave. It's like an echo that gets lost in the loud sound of the main tone.
This weak wave is called a Kelvin wave. It circles the planet like ripples on water from a thrown stone. Usually it's invisible: its frequency nearly matches the daily tide, and the signals merge. But during the great dust storm of Martian year 34, the Kelvin wave quadrupled in strength — from 2 to 8 pascals. For comparison, the daily tide at the same time reached 39 pascals.
Because of the resonance, the daily tide temporarily sped up: its period shortened from 24 to 23.5 Martian hours. Then the Kelvin wave quickly died out, and the day returned to normal. A computer model of the Martian climate reproduced these changes, confirming that the resonance was real, not a random sensor glitch.
Such wave coincidences are like two musicians who accidentally hit the same note and amplify the sound. On Mars, this helps predict dust storms and understand how the planet's atmosphere responds to heating.
Pressure on Mars is hundreds of times lower than on Earth: 8 pascals is like the weight of a small coin spread over a sheet of paper.