In this milestone 100th episode of Star Trails, we bring the cosmos back home.

After months of exploring distant stars, nebulae, and black holes, March begins with a tour of our own neighborhood: Mercury, Venus, Earth, and Mars, four rocky worlds born from the same protoplanetary disk 4.5 billion years ago, yet shaped into radically different outcomes.

We’ll visit Mercury, the tiny planet that helped confirm Einstein’s General Relativity and inspired the hunt for a phantom world called Vulcan. We’ll step into Venus, Earth’s “twin” turned runaway greenhouse furnace, and then we’ll zoom out on Earth itself as if we’re alien astronomers reading its oceans, oxygen, and technosignatures from afar. Finally, we’ll head to Mars, a planet that once hosted flowing water, may have been habitable long ago, and still tempts us with the unresolved  ...