Unraveling the Chaos of Aram
When Mars was still young, more than four billion years ago, a large asteroid sailed out of the sky and slammed into an area known today as western Arabia Terra. The object hit hard enough that it blasted a basin at least 280 kilometers (175 miles) wide. The basin is now named Aram Chaos.
As many millions of years passed, into this yawning bowl drifted sediments of many kinds - wind-blown dust, sand, and volcanic ash. The Martian climate was wetter then, so the crater-filling debris became saturated with water, which likely froze as the climate shifted and cooled.
Smooth layers with hematite (top) lie above chaotic terrain, a telltale signal the hematite is younger.
Eroded layers of rocks testify to the strength of the floods that poured out of Aram into the channel leading east into Ares Vallis.