Noctis Labyrinthus

Noctis Labyrinthus is located in the heart of Tharsis at the western end of the Valles Marineris, manifesting as a network of graben that extends in a spider-like network before coalescing into a coherent, relatively shallow graben swarm that curves in a semicircular fashion towards the south into the Claritas Rise. The graben are known as the Claritas Fossae beyond this point. ==Geology==

The Noctis Labyrinthus fracture zone is centered at the heart of the Tharsis Rise, dividing a plateau of Hesperian-Noachian age that is understood to be of a basaltic composition. In the chasmata of Noctis Labyrinthus, these pit crater chain collapse zones propagate directionally with a V-shaped tip, and can be used as an indicator of the direction into which magma withdraws from its underlying chamber. These V-tipped morphologies are generally found to propagate away from the center of the Tharsis Rise. Supporters of the lava tube hypothesis note that no evidence of lateral lava flows from the chasmata have been observed, suggesting against the notion that dikes must be required to underlie the surface of the modern-day collapse features as there is no evidence that such a near-surface intrusion has breached the surface in the Noctis Labyrinthus region. Based on CRISM spectral imagery, authors studying this depression have interpretatively identified the presence of: • iron-rich minerals such as hematite and goethite Calcium-rich pyroxenes have been spectrally observed elsewhere in the northern reaches of the Noctis Labyrinthus fracture zone. ==Observational history==

. In 1980, Philippe Masson of the University of Paris-Sud offered an integrated interpretation of the structural geochronology of Valles Marineris, Noctis Labyrinthus, and Claritas Fossae in light of imagery from Mariner 9 and the Viking Orbiter. In 2003, Daniel Mège (Pierre and Marie Curie University), Anthony C. Cook (University of Nottingham and the Smithsonian Institution), Erwan Garel (University of Maine in France), Yves Lagabrielle (University of Western Brittany), and Marie-Hélène Cormier (Columbia University) proposed a model for rifting on Mars initiated by the deflation of magma chambers, forming pit crater chains tracking directionally with simple graben. The researchers offered the first theoretical explanation as to how the chasmata of Noctis Labyrinthus formed. In 2012, a collaboration of French researchers Patrick Thollot, Nicolas Mangold, Véronique Ansan, and Stéphan Le Mouélic (University of Nantes), along with a cadre of American researchers including John F. Mustard (Brown University), Ralph E. Milliken (University of Notre Dame), and Scott Murchie (Applied Physics Laboratory) reported on an unnamed basin in southeastern Noctis Labyrinthus showing an extremely wide assemblage of minerals known to form across a wide range of pH and water availability conditions. The pit is the only one of its kind in Noctis Labyrinthus and has a greater variability than almost any other location yet observed on the planet. Using CRISM spectral data on HiRISE visual images for context, the researchers proposed that the variability of this pit is a result of hydrothermal alteration, with the dissolution of extant calcium-rich minerals (e.g. plagioclase) diminishing the acidity and thus kinds of minerals observed. The variability was explained without evoking a global warm and wet Martian climatic condition for the period. ==See also==