On 24 October 2025 image‑processing specialist Robert Wagner spotted a bright spot surrounded by a dark halo while running a routine quality check on a global map of the Moon. The anomaly turned out to be a fresh impact crater 222 metres wide on the Moon’s eastern near side, now named McGetchin after lunar scientist Tom McGetchin. The find, reported by NASA and described in two papers published in Science Advances on 16 September 2026, is the largest crater ever observed forming on any body in the solar system while under continuous monitoring.
Discovery and crater characteristics
Wagner, who works with the Lunar Reconnaissance Orbiter Camera (LROC) system, explained that the software he uses stacks hundreds of wide‑angle frames taken years apart, greying out unchanged terrain and highlighting new changes as bright or dark patches. Most alerts are false, caused by lighting shifts, but the bright spot inside a dark halo spanned hundreds of pixels—each pixel representing roughly the size of an American football field. The crater lies at 1.3536° N, 67.1765° E, just inside the outer ring of the Crisium basin, about 330 km from the edge of Mare Crisium.
Measurements from the LROC Narrow‑Angle Camera show a rim 231 m across at its widest (north‑northeast line) and 213 m at its narrowest (east‑southeast line). When the western and eastern halves are fitted separately, the western rim measures 230 m while the eastern rim is 214 m, suggesting excavation into loose regolith on one side and a coherent lava flow on the other. The crater is 43 m deep, giving a depth‑to‑diameter ratio of 0.19, typical for fresh craters of this size. Wall slopes average 24°, reaching up to 41° at the steepest sections. The floor is a hummocky patch 15 by 30 m, and a slump boulder 16 by 32 m rests about 10 m below the eastern rim.
The rim stands a median 7.7 m above the pre‑impact surface; roughly 4.6 m of that height is ejecta that piled up, with about 3.1 m of target material uplifted. The largest ejected boulder, measuring 13 by 9 by 3 m, sits on the southern rim, while a second boulder 8 by 7 by 2 m landed on the south‑eastern flank. Inside the crater, the brightest material in the 9 by 27 km surveyed frame is found, alongside darker patches interpreted as glassy, quenched impact melt possibly derived from mare basalt.
Impact energy, ejecta field and thermal signature
The impact occurred sometime between 11 April and 22 May 2024, a 41‑day window bracketed by before‑and‑after images. Assuming an impactor density of 3 g cm⁻³ and a speed of 15 km s⁻¹, the event released about 6.5 × 10¹⁰ kJ—more than an order of magnitude greater than the previous record holder, a 70‑m crater formed in 2012 that released roughly 2.4 × 10⁹ kJ. The energy ratio is about 27, and NASA describes the projectile as comparable in size to a three‑ to six‑storey building.
The bright halo around the crater indicated the splash of regolith. Stacked images revealed a brighter zone extending roughly 15 km from the impact site, and a fainter, patchier dark zone reaching beyond 120 km—about a thousand crater radii. In some places the ejecta forms a delicate lacy texture, suggesting that sparse clumps traveled far before landing. Eight kilometres west of the crater, a ridge 700 m high drops steeply toward Mare Spumans; the mare at its base appears up to 2.5 % darker, implying material was cleared from the ridge.
Thermal observations by LRO’s Diviner instrument, taken on 1 November 2025, identified a cold spot about 7 km across centered on McGetchin. The surface within this area cooled 8–9 K more during the lunar night than surrounding terrain, with a peak anomaly of 8.61 K. Researchers attribute the cooling to decompaction of the top centimetres to decimetres of regolith, which reduces heat retention. Proposed mechanisms for the decompaction include granular flow from secondary impacts, impact‑generated gas flow, and seismic shaking. Modeling suggests either a density gradient with a scale height of ~39 cm or a discrete decompacted layer ~3.2 cm thick.
McGetchin joins a set of 21 newly identified craters larger than 20 m catalogued by LRO. Every crater above roughly 30 m exhibits a detectable cold spot, and the magnitude of the temperature anomaly scales with crater size, although the relationship flattens for craters larger than about 100 m—making McGetchin the sole example in that regime. Cold spots are known to fade over 100 000 to two million years, so the observed anomaly likely represents the crater’s original thermal signature.
The discovery underscores the value of the 17‑year LRO image archive. Since 2009, LRO has catalogued at least 1 000 new craters, the largest of which previously measured 70 m. McGetchin’s 222‑m diameter therefore sets a new benchmark for impact events observed in real time, offering a rare laboratory for studying impact dynamics, ejecta distribution, and post‑impact thermal evolution on the Moon.
Steve Lopez is a Senior Editorial Columnist and Health & Public Policy reporter for News Raise. Steve focuses on healthcare advancements, medical technologies, and public health policies.
