Red Planet Report

[Editor’s note: From a paper by Christopher Hamilton and four co-authors recently published in the Journal of Geophysical Research.]

• The Hrad Vallis region of Mars includes evidence of both aqueous flooding and effusive volcanism

• Lava flows in the region provide evidence of inflation and may have interacted with ice deposits to generate hydrothermal activity

• Identification of ~50 m thick pahoehoe-like lava flows implies decadal-scale emplacement periods, similar to large lava flows on Earth

Major outflow channels on Mars may have been carved by either catastrophic aqueous floods or turbulent lava flows. Addressing the ambiguous origin of these channels is therefore important for constraining the hydrological and volcanic history of the planet. This study focuses on Hrad Vallis, which is a geologically recent (Amazonian-age) outflow channel located within the Elysium Volcanic Province, through a combination of mapping and modeling.

We find evidence for both aqueous flooding and effusive volcanism associated with this channel, indicating a complex hydrologic and geologic history. However, lava flows in this region are interpreted to be the products of pāhoehoe-like lava flow emplacement, similar to terrestrial lava flows on Earth in New Mexico and Hawaii, and not highly turbulent flows as previously suggested.

The identification of ~50 m thick pāhoehoe-like lava flows near Hrad Vallis implies a gradual formation process over the course of decades, and heat from these lava flows may have interacted with ground ice to produce meltwater and steam. Lava-water interactions on Mars are important because they could generate habitable environments for microbial organisms that have adapted for survival within hydrothermal systems. [More at link]