SS Weekly Highlight

Title: Great Expectations: Plans and Predictions for New Horizons Encounter With Kuiper Belt Object 2014 MU69(“Ultima Thule”)—-Short Story:

Strategic Plan Core Capability/Objective Reference: 2.3 (Understand Formation of Planets, Satellites and Rings, and Their Long-Term Evolution and Dynamics). On August 2nd 2018 the journal Geophysical Research Letters published a manuscript authored by Jeff Moore of NASA ARC, which included Dale Cruikshank, Ross Beyer, Oliver White, Carrie Chavez, and Orkan Umurhan as Ames-based co-authors.  The paper discusses the current state-of-knowledge for the ~30 km diameter, cold classical Kuiper Belt object 2014 MU69 informally named “Ultima Thule”, the target of a close encounter by NASA’s New Horizons spacecraft on 1 January 2019.  This encounter will be the first time a spacecraft has ever closely observed one of the free-orbiting small denizens of the Kuiper Belt.  Related to but not thought to have formed in the same region of the solar system as comets, it will also be the most distant, and most primitive body yet visited by spacecraft.  The paper begins with a brief overview of cold classical Kuiper Belt objects, of which Ultima is a prime example.  There is a short preview of the encounter plans and a summary of what is currently known about Ultima from Earth-based observations.  The paper then reviews the expectations and capabilities to evaluate Ultima’s composition, surface geology, structure, near space environment, small moons, rings, and the search for activity such as outgassing.  New Horizons will fly to within 3,500 km of Ultima, acquiring images with pixel scale resolutions significantly better than 100 m/pixel.  Topography will be derived from stereo imaging and body shape.  Spectroscopic observations will potentially detect water, methane, nitrogen, methanol, and ammonia, depending on their brightness and abundance on the surface.  This exploration will transform Kuiper Belt and Kuiper Belt object science from a purely astronomical regime, to a geological and geophysical regime, which radically changed paradigms when the same happened to asteroids and comets in past decades.  The accompanying figure shows an artist’s impression of Ultima. Earth observations of occultation of three stars by Ultima in 2017 determined that the object likely has a two-lobed shape, meaning it would be a close or contact binary.  The contact binary come 67P/Churyumov-Gerasimenko, observed by the Rosetta spacecraft, is shown for comparison.



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