Jay Melosh

Purdue University West Lafayette | Purdue · Department of Earth and Atmospheric Sciences

Double ridges are sprawling features observed globally across the icy surface of Europa. They consist of two topographic highs flanking a trough. The topographic relief of the ridges is approximately 100 m, and the ridges extend up to hundreds of kilometers in length. The interior structure and dynamics of Europa's ice shell are currently poorly co...

Atmospheres play an important role in ejecta deposition after an impact event. Many impact experiments and simulations neglect the effect of atmospheres. We simulate ejecta plumes created by craters with transient diameters of 2 and 20 km on Mars and Earth, to show the effect atmospheric density and crater size have on the strength of the interacti...

The formation and evolution of the terrestrial planets were shaped by a bombardment of large impactors in a cluttered early Solar System. However, various surface processes degrade impact craters, and the early impact history of the Moon and the ages of its ancient impact basins remain uncertain. Here we show that the porosity of the lunar crust, g...

Our collection of meteorites recovered here on Earth contain over 200 samples believe to have originated on Mars. It is commonly accepted that these rocks were launched as ejecta during the formation of impact craters. The majority of the meteorites are young and basaltic representing only a small fraction of the martian surface. Previous studies h...

We modified and justified the radar equation for ground penetration by including the backscattering effect. We propose a strawman system on an orbiter 50 km above the surface based on lunar conditions. The Tightly coupled dipole arrays antenna substantially reduces the size and mass and consists of an array with 8 × 8 cells on a light weight plate...

Lunar mascon basins exist for only a range of observed diameters. We modeled the full formation of South-Pole Aitken basin using a sequential two-code (hydrocode and Finite Element Model) approach to understand why this range does not extend to the largest lunar basin. Similar to previous work, we found that the best-fit hydrocode had impact parame...

Martian meteorites are currently the only rock samples from Mars available for direct study in terrestrial laboratories. Linking individual specimens back to their source terrains is a major scientific priority, and constraining the size of the impact craters from which each sample was ejected is a critical step in achieving this goal. During eject...

The impact of asteroids and comets with planetary surfaces is one of the most catastrophic, yet ubiquitous, geological processes in the solar system. The Chicxulub impact event, which has been linked to the Cretaceous-Paleogene (K-Pg) mass extinction marking the beginning of the Cenozoic Era, is arguably the most significant singular geological eve...

Future permanent habitats on the Moon may facilitate space exploration by serving as an outpost for manned missions to other planets. Safety and resilience of those habitats are the main concerns, especially given the existing dangerous conditions and hazards such as temperature fluctuation, radiation, seismic activity, and meteorite impacts. Under...

Lunar lava tubes are natural tunnels under the Moon surface that form when the liquid lava continues to flow underneath a cooled lava crust. The lunar lava tubes can provide a long-term shelter against hazards such as meteorite impacts, cosmic radiation and temperature fluctuations. Their existence is suggested by images taken of vertical holes “sk...

The dwarf planet Ceres exhibits a collection of craters that possess concentric fractures beyond the crater rim. These fractures typically range from a few hundred meters to a few kilometers in length and are less than 300 m wide. They occur preferentially on elevated regions around the crater and are located less than a crater radius beyond the ri...

The Moon’s isotopic composition is uncannily similar to Earth’s. This may be the signature of a magma ocean on Earth at the time of the Moon-forming giant impact, according to numerical simulations.

The megaregolith of the Moon is the upper region of the crust, which has been extensively fractured by intense impact bombardment. Little is known about the formation and evolution of the lunar megaregolith. Here we implement the Grady‐Kipp model for dynamic fragmentation into the iSALE shock physics code. This implementation allows us to directly...

Lunar lava tubes are important from various science perspectives and provide potential sites for future lunar base construction. Since the insides of lava tubes are shielded from cosmic radiation, particle implantation, and micro-meteorite bombardment, they are expected to have preserved original lava compositions, textures, and even volatiles that...

In this Article, the middle initial of author Kosei E. Yamaguchi (of the IODP–ICDP Expedition 364 Science Party) was missing and his affiliation is to Toho University (not Tohu University). These errors have been corrected online.

Multiring basins dominate the crustal structure, tectonics, and stratigraphy of the Moon. Understanding how these basins form is crucial for understanding the evolution of ancient planetary crusts. To understand how preimpact thermal structure and crustal thickness affect the formation of multiring basins, we simulate the formation of lunar basins...

Evidence for acoustic fluidization in the peak ring rocks of the Chicxulub impact structure.

GRAIL gravity data shows small-scale gravity anomalies radiating out from the Orientale basin between distances of ∼550 km (average distance to the Cordillera ring) and ∼1000 km. These radial gravity lineations are sometimes associated with secondary crater chains or catenae, of which the specific details of formation and their relation to the basi...

Large meteorite impact structures on the terrestrial bodies of the Solar System contain pronounced topographic rings, which emerged from uplifted target (crustal) rocks within minutes of impact. To flow rapidly over large distances, these target rocks must have weakened drastically, but they subsequently regained sufficient strength to build and su...

IODP-Expedition 364 Chicxulub Peak Ring Drilling

Cambridge Core - Planetary Science and Astrobiology - Chondrules - edited by Sara S. Russell

We present a simple and efficient implementation of a viscous creep rheology based on diffusion creep, dislocation creep and the Peierls mechanism in conjunction with an elasto-plastic rheology model into a shock-physics code, the iSALE open-source impact code. Our approach is based on the calculation of an effective viscosity which is then used as...

Lava tube exploration

An important new paper by Kurosawa and Genda [2017] reports a previously overlooked source of heating in low velocity meteorite impacts. Plastic deformation of the pressure-strengthened rocks behind the shock front dissipates energy, which appears as heat in addition to that generated across the shock wave itself. This heat source has surprisingly...

Major impact events have shaped the Earth as we know it. The Late Heavy Bombardment is of particular interest because it immediately precedes the first evidence of life. The reentry of impact ejecta creates numerous chemical byproducts, including biotic precursors such as HCN. This work examines the production of HCN during the Late Heavy Bombardme...

Impact cratering is likely a primary agent of regolith generation on airless bodies. Regolith production via impact cratering has long been a key topic of study since the Apollo era. The evolution of regolith due to impact cratering, however, is not well understood. A better formulation is needed to help quantify the formation mechanism and timesca...

The entry and subsequent breakup of the ~17–20 m diameter Chelyabinsk meteoroid deposited approximately 500 kT of TNT equivalent energy to the atmosphere, causing extensive damage that underscored the hazard from small asteroid impacts. The breakup of the meteoroid was characterized by intense fragmentation that dispersed most of the original mass....

The sparse occurrence of the mineral olivine in reflection spectra of the Moon's surface, as well as in deep-seated lunar rocks, has long puzzled lunar geologists because it is expected that the largest impact basins, particularly the 2500-km-diameter South Pole-Aitken (SPA) basin, should have exposed the lunar mantle. Using three-dimensional numer...

Intact lunar lava tubes offer a pristine environment to conduct scientific examination of the Moon's composition and potentially serve as secure shelters for humans and instruments. We investigated the SELENE Lunar Radar Sounder (LRS) data at locations close to the Marius Hills Hole (MHH), a skylight potentially leading to an intact lava tube, and...

Extraterrestrial habitation has long been the object of science fiction, and experts in the fields of science and engineering have proposed many designs for a lunar base. The research conducted has focused on either structural stability, radiation protection, or meteorite-impact vulnerabilities, but rarely have these been considered together. The R...

The design of self-sustaining lunar habitats is a challenge primarily due to the Moon's lack of atmospheric protection and hazardous environment. To assure safe habitats that will lead to further lunar and space exploration, it is necessary to assess the different hazards faced on the Moon such as meteoroid impacts, extreme temperatures, and radiat...

Impact geologists have long assumed that shock metamorphic features, such as planar fractures and Planar Deformation Features (PDFs) in quartz are reliable indicators of an extraterrestrial impact. A new paper by Chen et al. (2017) now shows that such features might arise in terrestrial lightning strikes, thus raising the bar for identification of...

We used gravity mapping observations from NASA’s Gravity Recovery and Interior Laboratory (GRAIL) to detect, characterize and validate the presence of large impact craters buried beneath the lunar maria. In this paper we focus on two prominent anomalies detected in the GRAIL data using the gravity gradiometry technique. Our detection strategy is ap...

Introduction: In 2009, three huge pits were discovered on the Moon in image data acquired by the SELENE Terrain Camera. Their diameters and depths are several tens of meters or more.[1-3] They are possible skylight holes opening on large subsurface caverns such as lava tubes, [1] by analogy with similar pits found on Mars.[4] This possibility was e...

NASA's GRAIL mission employed twin spacecraft in polar orbits around the Moon to measure the lunar gravity field at unprecedentedly high accuracy and resolution. The low spacecraft altitude in the extended mission enables the detection of small-scale surface or subsurface features. We analyzed these data for evidence of empty lava tubes beneath the...

Because of the high energies involved, giant impacts that occur during planetary accretion cause large degrees of melting. The depth of melting in the target body after each collision determines the pressure and temperature conditions of metal-silicate equilibration and thus geochemical fractionation that results from core-mantle differentiation. T...

Major impact events have drastically altered the evolution of life on Earth. The reentry of ejecta formed from these events can trigger widespread chemical changes to the atmosphere on a global scale. This mechanism was proposed as a source of HCN during the Late Heavy Bombardment (LHB), 4.1 to 3.8 billion years ago. Significant concentrations of H...

Here we address the comments by Iverson [2016] on our recent work concerning the reduction of friction in long runout landslides [Johnson et al., 2016]. Iverson [2016] questions the veracity of models and suggests that high basal pore fluid pressure is the dominant mechanism reducing friction in long runout landslides. The main goal of our work was...

TitOn the origin of Orientale basinle Orientale basin is a major impact crater on the Moon, which is hard to see from Earth because it is right on the western edge of the lunar nearside. Relatively undisturbed by later events, Orientale serves as a prototype for understanding large impact craters throughout the solar system. Zuber et al. used the G...

On the origin of Orientale basin Orientale basin is a major impact crater on the Moon, which is hard to see from Earth because it is right on the western edge of the lunar nearside. Relatively undisturbed by later events, Orientale serves as a prototype for understanding large impact craters throughout the solar system. Zuber et al. used the Gravit...

Mounting evidence from the SELENE, LRO, and GRAIL spacecraft suggests the presence of vacant lava tubes under the surface of the Moon. GRAIL evidence, in particular, suggests that some may be more than a kilometer in width. Such large sublunarean structures would be of great benefit to future human exploration of the Moon, providing shelter from th...

The abundance of moderately siderophile elements (“iron-loving”; e.g. Co, Ni) in the Earth's mantle is 10 to 100 times larger than predicted by chemical equilibrium between silicate melt and iron at low pressure, but it does match expectation for equilibrium at high pressure and temperature. Recent studies of differentiated planetesimal impacts ass...

By the time icy objects grow to about the mass of Europa and silicate bodies grow to approximately lunar mass, a large high-speed impact can generate an intact melt region that allows the dense material to gravitationally segregate, forming a large density anomaly. If this anomaly generates sufficient differential stress, it rapidly segregates to t...

Comet 103P/Hartley 2 has diurnally controlled, CO2-driven activity on the tip of the small lobe of its bilobate nucleus. Such activity is unique among the comet nuclei visited by spacecraft, and suggests that CO2 ice is very near the surface, which is inconsistent with our expectations of an object that thermophysically evolved for ∼45 million year...

Pluto's surface is surprisingly young and geologically active(1). One of its youngest terrains is the near-equatorial region informally named Sputnik Planum, which is a topographic basin filled by nitrogen (N-2) ice mixed with minor amounts of CH4 and CO ices(1). Nearly the entire surface of the region is divided into irregular polygons about 20-30...

Campbell et al. (1995) modeled long runout landslides as granular flow using a soft particle code. Their model essentially simulates landslides from first principles, and although no fluid or obvious mechanism for reduction of friction is included, the model successfully reproduced many field observations of landslides (e.g., the preservation of so...

With the goal of expanding human presence beyond Earth, sub-surface empty lava tubes on other worlds form ideal candidates for creating a permanent habitation environment safe from cosmic radiation, microm-eteorite impacts and temperature extremes. In a step towards Mars exploration , the Moon offers the most favorable pathway for lava tube explora...

The South Pole-Aitken (SP-A) basin is the largest observable impact structure on the Moon. The 2500 km diameter SP-A basin was likely formed by a 200 to 300 km diameter asteroid striking at an oblique angle, giving the basin its elliptical shape. The current orientation of the basin suggests the impactor traveled from south to north at an angle fro...

Manual for the Dellen release of the iSALE shock physics code: A multi-material, multi-rheology shock physics code for simulating impact phenomena in two and three dimensions.

Manual for the Dellen release of the iSALE shock physics code: A multi-material, multi-rheology shock physics code for simulating impact phenomena in two and three dimensions.

The Chicxulub impact 66.0Ma ago initiated the second biggest extinction in the Phanerozoic Eon. The cause of the concurrent oceanic nitrogen isotopic anomaly, however, remains elusive. The Chicxulub impactor struck the Yucatán peninsula, ejecting 2×1015kg of molten and vaporized rock that reentered globally as approximately 1023 microscopic spherul...

We model the formation of lunar complex craters and investigate the effect of preimpact porosity on their gravity signatures. We find that while preimpact target porosities less than ~7% produce negative residual Bouguer anomalies (BAs), porosities greater than ~7% produce positive anomalies whose magnitude is greater for impacted surfaces with hig...

Observations from the Gravity Recovery and Interior Laboratory (GRAIL) mission indicate a marked change in the gravitational signature of lunar impact structures at the morphological transition, with increasing diameter, from complex craters to peak-ring basins. At crater diameters larger than ~200 km, a central positive Bouguer anomaly is seen wit...

In recent years, imagery from JAXA’s SElenological and ENgineering Explorer (SELENE) spacecraft and NASA’s Lunar Reconnaissance Orbiter (LRO) has revealed the presence of uncollapsed voids and caves near the lunar surface. Gravity studies based on data from the Gravity Recovery And Interior Laboratory (GRAIL) spacecraft have also revealed possible...

We have analyzed the Bouguer anomaly (BA) of ~1200 complex craters in the lunar highlands from Gravity Recovery and Interior Laboratory (GRAIL) observations. The BA of these craters is generally negative, though positive BA values are observed, particularly for smaller craters. Crater BA values scale inversely with crater diameter, quantifying how...

Previously proposed mechanisms have difficulty explaining the disruption of Comet C/2012 S1 (ISON) as it approached the Sun. We describe a novel cometary disruption mechanism whereby comet nuclei fragment and disperse through dynamic sublimation pressure, which induces differential stresses within the interior of the nucleus. When these differentia...

NASA's dual Gravity Recovery and Interior Laboratory (GRAIL) spacecraft have globally mapped the lunar gravity field at unprecedented resolution. Soderblom et al. [2015] made a comprehensive analysis of the residual and central uplift Bouguer gravity anomalies associated with more than 5200 lunar craters. There were two main observations that are r...

Introduction: As a part of NASA's Discovery Program, the Gravity Recovery and Interior Laboratory (GRAIL) vehicles were launched in September 2011. The sister spacecraft, Ebb and Flow, mapped lunar gravity to an unprecedented precision [1]. High resolution data is currently being utilized to gain a greater understanding of the Moon's interior. Thro...

Introduction and Background: NASA's dual Gravity Recovery and Interior Laboratory (GRAIL) [1] spacecraft have globally mapped the lunar gravity field at unprecedented resolution; this has enabled the global study of small craters up to the largest basins. Results have shown that the lunar crust has a large range of porosities with an average value...

Introduction. One of the primary objectives of the Gravity Recovery and Interior Laboratory (GRAIL) mission [1] was to use the Bouguer gravity signals of impact craters to not only learn about the subsurface disposition beneath craters (e.g., extent of brecciation), but also to use these crater gravity signals as probes into the structure of the cr...

Chondrules are the millimetre-scale, previously molten, spherules found in most meteorites. Before chondrules formed, large differentiating planetesimals had already accreted. Volatile-rich olivine reveals that chondrules formed in extremely solid-rich environments, more like impact plumes than the solar nebula. The unique chondrules in CB chondrit...