Initial results from the New Horizons exploration of 2014 MU ₆₉ , a small Kuiper Belt object

Abstract

The Kuiper Belt is a distant region of the outer Solar System. On 1 January 2019, the New Horizons spacecraft flew close to (486958) 2014 MU69, a cold classical Kuiper Belt object approximately 30 kilometers in diameter. Such objects have never been substantially heated by the Sun and are therefore well preserved since their formation. We describe initial results from these encounter observations. MU69 is a bilobed contact binary with a flattened shape, discrete geological units, and noticeable albedo heterogeneity. However, there is little surface color or compositional heterogeneity. No evidence for satellites, rings or other dust structures, a gas coma, or solar wind interactions was detected. MU69’s origin appears consistent with pebble cloud collapse followed by a low-velocity merger of its two lobes.

The geology and geophysics of Kuiper Belt object (486958) Arrokoth

“…S3 and Table S3)). Comets 19P, 67P, and 103P appear to be highly elongated bilobate objects, suggesting the merger of two distinct bodies, as has been proposed for Arrokoth (1,18), though for comets it is also possible that thermal evolution has generated this shape (e.g., 60). Except for 67P, whose bulk density is 538 ± 1 kg m -3 (16), the densities of the other JFC nuclei are uncertain by a factor of two or more, but all are consistent with ~500 kg m -3 (61), which implies average bulk porosities of ~50-80%.…”

“…On 2019 January 1 at 05: 33:22 Universal Time (UT) the New Horizons spacecraft flew past the Kuiper Belt object (KBO) (486958) Arrokoth (2014 MU69, originally nicknamed "Ultima Thule"), at a distance of 3538 km (1). Arrokoth is a contact binary consisting of two distinct lobes, connected by a narrow neck.…”

“…Arrokoth is a contact binary consisting of two distinct lobes, connected by a narrow neck. Based on its orbital semi-major axis, low eccentricity and inclination (2), and its albedo and color (1,3), Arrokoth is classified as a member of the dynamically cold, non-resonant "cold classical" KBO (CCKBO) population, and probably a member of the tight orbital clustering of CCKBOs known as the kernel (4). There is no known mechanism for transporting the majority of these objects onto these nearly circular orbits, so they are thought to have formed in situ and remained dynamically undisturbed since the formation of the Solar System.…”

“…Initial results from this flyby (1) were based on early data downlinked from the spacecraft. Since then, additional data have been downlinked, including: (i) the highest-resolution images from the flyby, taken with the narrow-angle Long-Range Reconnaissance Imager (LORRI) camera (7).…”

“…Since then, additional data have been downlinked, including: (i) the highest-resolution images from the flyby, taken with the narrow-angle Long-Range Reconnaissance Imager (LORRI) camera (7). These LORRI images have a pixel scale which is 4 times finer (33 m pixel -1 ) than the 130 m pixel -1 of previously-available Multicolor Visible Imaging Camera (MVIC) (8) images (1), though due to smear and a lower signal-to-noise ratio (SNR), the effective resolution of the LORRI images is only about 2 times better than the MVIC images; (ii) Additional LORRI images from earlier approach epochs, with higher SNR than previously-downlinked data; (iii) Improved LORRI distant approach rotational coverage, constraining the shape and rotational parameters; and (iv) Additional satellite and ring search data from LORRI and MVIC. See (9) for image processing details.…”