Kevin Williams may have found one of the best places on Mars to look for past or present life. The region lies at the merger of two ancient riverbeds, the Samara and Paraná-Loire Valles systems. But the past presence of water is only part of the reason why the area intrigues Williams and his colleagues at the Smithsonian Institution in Washington, D.C.
Visible and infrared images taken by two Mars-orbiting spacecraft reveal that a kilometer-high edifice, probably a volcano, lies at the confluence. Moreover, the appearance of soil at the site indicates that when the volcano erupted, its lava encountered liquid or frozen water. Williams presented the findings March 15 at the annual Lunar and Planetary Science Conference in Houston.
On Earth, the combination of volcanic heat and water can create a haven for primitive life (SN: 1/29/05, p. 69: Available to subscribers at Hungry for Hydrogen: Microbes in hot springs feed on unlikely source), and the same might be true on Mars, Williams notes.
Evidence of an interaction between lava and water at the site comes from concentric ripples of Martian soil near the top of the edifice, notes Williams. Other researchers have found ripples at the site of another dried-up Martian channel, Mangala Valles. On Earth, such ripples, called sand waves, aren’t sculpted by wind as dunes are. Rather, they’re created when lava boils ice or water in staccato explosions. Mount St. Helens, for instance, has sand waves near its peak.