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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| 486958 Arrokoth | 3/8 | https://en.wikipedia.org/wiki/486958_Arrokoth | reference | science, encyclopedia | 2026-05-05T13:09:12.451441+00:00 | kb-cron |
=== Craters === The surface of Arrokoth is lightly cratered and smooth in appearance. Arrokoth's surface has few small craters (from 1 km (0.62 mi) in size to the limits of photographic resolution), implying a paucity of impacts throughout its history. The occurrence of impact events in the Kuiper belt is thought to be uncommon, with a very low impact rate over the course of one billion years. Due to the slower orbital speeds of Kuiper belt objects, the speed of objects impacting Arrokoth is expected to be low, with typical impact speeds around 300 m/s (980 ft/s). At such slow impact speeds, large craters on Arrokoth are expected to be rare. With a low frequency of impact events along with the slow speeds of impacts, Arrokoth's surface would remain preserved since its formation. The preserved surface of Arrokoth could possibly give hints to its formation process, as well as signs of accreted material. Numerous small pits on Arrokoth's surface were identified in high resolution images from the New Horizons spacecraft. The size of these pits are measured at about 700 m (2,300 ft) across. The exact cause of these pits is unknown; several explanations for these pits include impact events, the collapse of material, the sublimation of volatile materials, or the venting and escape of volatile gases from the interior of Arrokoth.
=== Surface features ===
The surfaces of each lobe of Arrokoth display regions of varying brightness along with various geological features such as troughs and hills. These geological features are thought to have originated from the clumping of smaller planetesimals that come to form the lobes of Arrokoth. The brighter regions of Arrokoth's surface, especially its bright lineation features, are thought to have resulted from the deposition of material that have rolled down from hills on Arrokoth, as surface gravity on Arrokoth is sufficient for this to occur. The smaller lobe, Weeyo, bears a large depression feature named 'Sky' (previously dubbed 'Maryland' after the home state of the New Horizons team). Assuming Sky has a circular shape, its diameter is 6.7 km (4.2 mi), with a depth of 0.51 km (0.32 mi). Sky is likely an impact crater that was formed by an object 700 m (2,000 ft) across. Two notably bright streaks of similar size are present within Sky, and may be remnants of avalanches where bright material rolled into the depression. Four subparallel troughs are present near the terminator of Weeyo, along with two possible kilometer-sized impact craters on the rim of Sky. The surface of Weeyo exhibits bright mottled regions separated by broad, dark regions (dm) which may have undergone scarp retreat, in which they were eroded due to the sublimation of volatiles, exposing lag deposits of darker material irradiated by sunlight. Another bright region (rm), located at the equatorial end of Weeyo, exhibits rough terrain along with several topographic features that have been identified as possible pits, craters, or mounds. Weeyo does not display distinct units of rolling topography near Sky, likely as a result of resurfacing caused by the impact event that created the crater. As on Weeyo, troughs and pit crater chains are also present along the terminator of the larger lobe Wenu. Wenu consists of eight distinctive units or blocks of rolling topography, each similarly sized at around 5 km (3.1 mi). The units are separated by relatively bright boundary regions. The similar sizes of the units suggests that each was once a small planetesimal, and that they coalesced to form Wenu. The planetesimals are expected to have accreted slowly by astronomical standards (at speeds of several meters per second), though they must have a very low mechanical strength in order to merge and form compact bodies at these speeds. The central unit ('mh') is encircled by a bright annular feature, Kaʼan Arcus (initially dubbed "The Road to Nowhere"). From stereographic analysis, the central unit appears to be relatively flat compared to the surrounding units. Stereographic analysis of Arrokoth has also shown that one particular unit located at Wenu's limb ('md') appears to have a higher elevation and tilt than the others. Akasa Linea, the neck region connecting the two lobes, has a brighter and less red appearance than the surfaces of either lobe. The brightness of Akasa Linea is likely due to a composition of a more reflective material than the surfaces of the lobes. One hypothesis suggests the bright material originated in the deposition of small particles that had fallen from the lobes over time. Since Arrokoth's center of gravity lies between the lobes, small particles are likely to roll down the steep slopes toward the center between each lobe. Another proposal suggests the bright material is produced by the deposition of ammonia ice. Ammonia vapor present on the surface of Arrokoth would solidify around Akasa Linea, where gases cannot escape due to the concave shape of the neck. The brightness of Akasa is thought to be maintained by high seasonal axial tilt as Arrokoth orbits around the Sun. Over the course of its orbit, Akasa Linea is shadowed when the lobes are coplanar to the direction of the Sun, at which times the neck region receives no sunlight, cooling and trapping volatiles in the region. In May 2020, the IAU's Working Group for Planetary System Nomenclature (WGPSN) formally established a naming theme for all features of Arrokoth, which are to be named after words for "sky" in the languages of the world, past and present. In 2021, the first few names were approved, including Sky Crater on the small lobe, later named Weeyo Lobus. In 2022, Kaʼan Arcus was approved for the circular arc on Wenu Lobus. On 17 December 2025, Akasa Linea was changed to Akasa Collum.