Liquid water inferred on present-day Mars Available to Purchase

Morphological evidence abounds for the flow of liquid water on ancient Mars; see, for example, the article by Bruce Jakosky and Michael Mellon, Physics Today, April 2004, page 71. However, little definitive evidence for it exists on today’s surface. What surface water Mars holds has long been thought to reside as ice at its poles. In 2010 the Mars Reconnaissance Orbiter (MRO) spotted features known as recurring slope lineae that are consistent with transient flow: The dark, narrow streaks—the ones in the figure are hundreds of meters long—elongate on warm slopes in the spring and summer when their temperatures exceed about 250 K, fade and vanish in colder seasons, and reappear annually. Georgia Institute of Technology doctoral student Lujendra Ojha and his colleagues have now analyzed absorption spectra taken by MRO of four separate regions containing the streaks. They found signatures of a family of hydrated...