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The low‐degree shape of Mercury
Author(s) -
Perry Mark E.,
Neumann Gregory A.,
Phillips Roger J.,
Barnouin Olivier S.,
Ernst Carolyn M.,
Kahan Daniel S.,
Solomon Sean C.,
Zuber Maria T.,
Smith David E.,
Hauck Steven A.,
Peale Stanton J.,
Margot JeanLuc,
Mazarico Erwan,
Johnson Catherine L.,
Gaskell Robert W.,
Roberts James H.,
McNutt Ralph L.,
Oberst Juergen
Publication year - 2015
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/2015gl065101
Subject(s) - mercury (programming language) , geoid , planet , geodesy , spacecraft , geology , latitude , altimeter , southern hemisphere , oblate spheroid , northern hemisphere , polar , geophysics , physics , astrobiology , atmospheric sciences , astronomy , climatology , atomic physics , computer science , programming language , measured depth
The shape of Mercury, particularly when combined with its geoid, provides clues to the planet's internal structure, thermal evolution, and rotational history. Elevation measurements of the northern hemisphere acquired by the Mercury Laser Altimeter on the MErcury Surface, Space ENvironment, GEochemistry, and Ranging spacecraft, combined with 378 occultations of radio signals from the spacecraft in the planet's southern hemisphere, reveal the low‐degree shape of Mercury. Mercury's mean radius is 2439.36 ± 0.02 km, and there is a 0.14 km offset between the planet's centers of mass and figure. Mercury is oblate, with a polar radius 1.65 km less than the mean equatorial radius. The difference between the semimajor and semiminor equatorial axes is 1.25 km, with the long axis oriented 15° west of Mercury's dynamically defined principal axis. Mercury's geoid is also oblate and elongated, but it deviates from a sphere by a factor of 10 less than Mercury's shape, implying compensation of elevation variations on a global scale.