The Floods of Iani Chaos
A tangle of mesas, buttes, and broken ground called Iani Chaos lies sprawled across one of Mars' longest outflow channels, the Uzboi-Ladon-Margaritifer system. This channel empties into the northern lowlands through Ares Vallis.
Iani resembles a broken slab of rock, and its shattered appearance led scientists years ago to classify it as "chaotic terrain." Wherever scientists see chaotic terrain - which occurs in numerous places on Mars - they also see signs of catastrophic floods. As they reconstruct it, huge amounts of groundwater were released when geologic faults cracked open the surface of Iani. The escaping water caused the land to subside, collapse, and erode, leaving the badlands seen today.
Iani Chaos was once in the list of landing sites that scientists are evaluating as targets for the Mars Science Laboratory (MSL), NASA's next-generation rover, planned for launch in 2011. While not chosen for MSL, Iani still offers scientific attractions to keep it on lists of potential landing sites for future rover spacecraft.
Water's role in Iani Chaos is the biggest factor drawing the interest of scientists. The main image is a mosaic of infrared photos taken by the Thermal Emission Imaging System (THEMIS) on NASA's Mars Odyssey orbiter. In addition to the collapsed landscape, however, instruments on two other Mars-orbiting spacecraft found mineralogical evidence for abundant water here.
The Thermal Emission Spectrometer (TES) on Mars Global Surveyor spotted hematite in Iani. Not long after, the OMEGA spectrometer on the European Space Agency's Mars Express orbiter detected sulfate minerals (likely gypsum) in many of the places where TES found hematite. Both hematite (an iron-oxide mineral) and sulfates require substantial water to form.
No one knows if Mars ever had life, or if it did where it was most abundant. But scientists are agreed that settling the issue will likely require samples brought back to Earth for laboratory study, which calls for a rover to be sent someday.