We'll never stop being fascinated by Mars. It's kind of like a failed Earth. It appears as if billions of years ago Mars was warm, wet, and habitable. That ended when its interior cooled and its geodynamo failed.

When its geodynamo failed, its magnetic shield failed. The full force of the Sun bore down on the unfortunate planet, and its warming atmosphere was lost to space.

The loss of atmosphere wasn't the only change. Mars had a powerful volcanic past, and the prominent volcanoes in Tharsis Montes prove that. But the planet is largely believed to have left its volcanic past behind as a consequence of cooling.

But there's growing evidence that the planet isn't totally dormant. Recent evidence from missions like InSight and the ExoMars Trace Gas Orbiter suggest some ongoing activity. InSight detected more than 1300 Marsquakes, and the Trace Gas Orbiter detected hydrochloric acid.

Hydrochloric acid (HCl) is a highly corrosive acid with multiple natural sources, including atmospheric ones.…