{{Short description|Mountain on the Moon}} {{Infobox mountain | name = Mons Hansteen | image = Mons Hansteen 4149 h2.jpg | image_caption = Lunar Orbiter 4 image | elevation = | listing = Lunar mountains | translation = Hansteen mountain | language = Latin | location = Near side of the Moon | coordinates = {{Lunar coords and quad cat|12.1|S|50.0|W}} | type = Lunar dome | age = }}

'''Mons Hansteen''' is a mountain on the Moon, also known as Hansteen Alpha (α), named after Christopher Hansteen. It is roughly triangular in shape and occupies an area about 30&nbsp;km across on the western margin of Oceanus Procellarum, southeast of the crater Hansteen and north of the dark-floored crater Billy. It is thought to be an extrusion of volcanic material that is younger than the crater Hansteen, with most of surface volcanic ash been deposited 3.5-3.74 billion years ago.<ref>{{cite journal | doi=10.1016/j.icarus.2016.08.013 | title=Hansteen Mons: An LROC geological perspective | journal=Icarus | series=Lunar Reconnaissance Orbiter - Part II | date=February 2017 | volume=283 | pages=254–267 | last1=Boyce | first1=Joseph M. | last2=Giguere | first2=Thomas A. | last3=Hawke | first3=B. Ray | last4=Mouginis-Mark | first4=Peter J. | last5=Robinson | first5=Mark S. | last6=Lawrence | first6=Samuel J. | last7=Trang | first7=David | last8=Clegg-Watkins | first8=Ryan N. | bibcode=2017Icar..283..254B | doi-access=free }}</ref> The Mons Hansteen belongs to rare class of non-mare moon volcanoes.<ref>{{citation|arxiv=1409.1209|year=2014|title=Evidence for explosive silicic volcanism on the Moon from the extended distribution of thorium near the Compton-Belkovich Volcanic Complex|doi=10.1002/2014JE004719 |last1=Wilson |first1=J. T. |last2=Eke |first2=V. R. |last3=Massey |first3=R. J. |last4=Elphic |first4=R. C. |last5=Jolliff |first5=B. L. |last6=Lawrence |first6=D. J. |last7=Llewellin |first7=E. W. |last8=McElwaine |first8=J. N. |last9=Teodoro |first9=L. F. A. |journal=Journal of Geophysical Research: Planets |volume=120 |pages=92–108 |s2cid=52241264 }}</ref>

==Composition== The extruded material is significantly enriched in silica, and strongly depleted in iron and titanium oxides compared to surrounding mare terrain.<ref>[https://www.lpi.usra.edu/meetings/lpsc2011/pdf/1652.pdf HANSTEEN ALPHA: A SILICIC VOLCANIC CONSTRUCT ON THE MOON.]</ref> Initially, it was believed its lavas are not as evolved as in Compton–Belkovich Thorium Anomaly,<ref>{{cite journal | url=https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2002JE002013 | doi=10.1029/2002JE002013 | title=Hansteen Alpha: A volcanic construct in the lunar highlands | date=2003 | last1=Hawke | first1=B. Ray | last2=Lawrence | first2=D. J. | last3=Blewett | first3=D. T. | last4=Lucey | first4=P. G. | last5=Smith | first5=G. A. | last6=Spudis | first6=P. D. | last7=Taylor | first7=G. J. | journal=Journal of Geophysical Research: Planets | volume=108 | issue=E7 | page=5069 | bibcode=2003JGRE..108.5069H }}</ref> but by 2004 the low thorium enrichment signal was attributed to small size of volcanic complex, making it composition compatible with highly processed silicic lavas.<ref>[https://www.lpi.usra.edu/meetings/lpsc2004/pdf/1727.pdf REVISITING THE INTERPRETATION OF THORIUM ABUNDANCES AT HANSTEEN ALPHA.]</ref> By 2013, a patchy deposits of magnesium spinel were detected in the central and western parts of the volcanic dome.<ref>[https://www.lpi.usra.edu/meetings/lpsc2013/pdf/1348.pdf EXPOSURES OF Mg-SPINEL ON AN EVOLVED SILICIC LITHOLOGY HANSTEEN ALPHA ON THE MOON]</ref> The spinel-rich areas are associated with boulder fields, and fringed by areas showing a sign of hydration,<ref>[https://www.hou.usra.edu/meetings/lpsc2017/pdf/2104.pdf MG-SPINEL EXPOSURES WITHIN SILICA RICH SETTING ON HANSTEEN ALPHA: PROBING THE GEOLOGIC CONTEXT]</ref> with 4-8% of mineral by weight been hydroxylated.<ref>[https://www.hou.usra.edu/meetings/lpsc2015/pdf/1400.pdf ENDOGENIC WATER/HYDROXYL ANOMALY ASSOCIATED WITH LUNAR SILICIC DOMES DETECTED BY CHANDRAYAAN-I MOON MINERALOGY MAPPER (M3) INSTRUMENT AND ITS IMPLICATIONS.]</ref>

The average bulk density of material in Mons Hansteen is extremely low, been equal only to 1500–2000&nbsp;kg/m<sup>3</sup>.<ref>[https://www.hou.usra.edu/meetings/lpsc2016/pdf/1722.pdf The Bulk Density of the Small Lunar Volcanos Gruithuisen Delta and Hansteen Alpha: Implications for Volcano Composition and Petrogenesis]</ref>

==See also== *Volcanism on the Moon

==References== {{reflist}}

==External links== * [http://lroc.sese.asu.edu/posts/972 Mons Hansteen: A Window into Lunar Magmatic Processes], Lunar Reconnaissance Orbiter Camera (LROC) article, Posted by Brett Denevi on April 10, 2017

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