Hebrus Valles (HV) and Hephaestus Fossae (HF) are well-preserved channels on Mars, located in southeastern Utopia Planitia, formed during the Early Amazonian period (starting about 3 billion years ago). These channels were shaped by multiple water flows and are carved into bedrock, displaying various morphologies. Despite their clear signs of water activity, the origin and fate of the water, as well as the sediments involved, remain poorly understood, leaving a gap in knowledge about Martian geologic processes.

We analyzed these channels using high-resolution visible and infrared imagery, radar data, and geologic mapping, reconstructing the geological processes behind the channels' formation. Our findings show that HV and HF are around 2.2 billion years and 1.9 billion years old, respectively, indicating prolonged aqueous activity on Mars during the Amazonian period.

The channels originate from two deep pits within the Utopia lower unit, where elongated ridges suggest magmatic intrusions fractured a pressurized aquifer's cryospheric seal. We propose that the water release was driven by either magmatic heating or hydraulic pressure in the aquifer. These long-lived discharge events highlight the role of magmatic processes in Mars’ water history.