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Eugene Merle Shoemaker

Publications and source records attributed to Eugene Merle Shoemaker.

At least 37 records · Page 2Linked to original sources
USGS1995

Highly integrated Pluto payload system (HIPPS): A sciencecraft instrument for the Pluto mission

We describe the design concept for the highly integrated Pluto payload system (HIPPS): a highly integrated, low-cost, light-weight, low-power instrument payload designed to fly aboard the proposed NASA Pluto flyby spacecraft destined for the Pluto/Charon system. The HIPPS payload is designed to accomplish all of the Pluto flyby prime (IA) science objectives, except radio science, set forth by NASA's Outer Planets Science Working Group (OPSWG) and the Pluto Express Science Definition Team (SDT). HIPPS contains a complement of three instrument components within one common infrastructure; these are: (1) a visible/near UV CCD imaging camera; (2) an infrared spectrograph; and (3) an ultraviolet spectrograph. A detailed description of each instrument is presented along with how they will meet the IA science requirements.

Conference Paper↗
USGS1995

The Hubble Space Telescope (HST) observing campaign on comet Shoemaker-Levy 9

The Hubble Space Telescope made systematic observations of the split comet P/Shoemaker-Levy 9 (SL9) (P designates a periodic comet) starting in July 1993 and continuing through mid-July 1994 when the fragments plunged into Jupiter's atmosphere. Deconvolutions of Wide Field Planetary Camera images indicate that the diameters of some fragments may have been as large as ∼2 to 4 kilometers, assuming a geometric albedo of 4 percent, but significantly smaller values (that is, < 1 kilometer) cannot be ruled out. Most of the fragments (or nuclei) were embedded in circularly symmetric inner comae from July 1993 until late June 1994, implying that there was continuous, but weak, cometary activity. At least a few nuclei fragmented into separate, condensed objects well after the breakup of the SL9 parent body, which argues against the hypothesis that the SL9 fragments were swarms of debris with no dominant, central bodies. Spectroscopic observations taken on 14 July 1994 showed an outburst in magnesium ion emission that was followed closely by a threefold increase in continuum emission, which may have been caused by the electrostatic charging and subsequent explosion of dust as the comet passed from interplanetary space into the jovian magnetosphere. No OH emission was detected, but the derived upper limit on the H 2 O production rate of ∼10 27 molecules per second does not necessarily imply that the object was water-poor.

Science↗
USGS1994

The Clementine mission to the Moon: Scientific overview

In the course of 71 days in lunar orbit, from 19 February to 3 May 1994, the Clementine spacecraft acquired just under two million digital images of the moon at visible and infrared wavelengths. These data are enabling the global mapping of the rock types of the lunar crust and the first detailed investigation of the geology of the lunar polar regions and the lunar far side. In addition, laser-ranging measurements provided the first view of the global topographic figure of the moon. The topography of many ancient impact basins has been measured, and a global map of the thickness of the lunar crust has been derived from the topography and gravity.

Science↗
USGS1994

Correlation and age of the Upper Jurassic Morrison Formation from magnetostratigraphic analysis

The magnetostratigraphy of the Morrison Formation of east-central New Mexico resembles that of three western Colorado sections. Magnetic polarity and lithology agree among the sections, indicating the correlation potential of magnetostratigraphy in this lithologically complex formation. Both magnetostratigraphy, lithology, and paleopoles divide the formation into two parts. The lower sandstone-dominated portion was deposited during a time of relatively equal lengths normal and reversed polarity intervals, whereas the upper mudstone (Brushy Basin) portion was deposited during predominantly reversed polarity with interspersed short normal intervals. The four magnetostratigraphic sequences yield a composite Morrison Formation magnetostratigraphy. Upper Morrison polarity correlates well with the polarity pattern of the marine magnetic anomaly M-sequence and indicates that the Brushy Basin Member is Kimmeridgian and earliest Tithonian in age. The correlation suggests that lower part of the formation is at least Oxfordian in age. Two pole positions were obtained from the New Mexico Morrison Formation. The lower sandstone-dominated part of the formation gives a different paleopole from the mostly mudstone upper portion of the formation. This difference is quite similar to observation of two pole positions in the Colorado Morrison Formation. The similarity between New Mexico and Colorado indicates that the base level change within the formation, the change from sandstone and mudstone to nearly purely mudstone deposition, was approximately synchronous in the two areas. The presence of two different paleopoles suggests an hiatus in the formation. The hiatus in sedimentation coincides with the base level change, and the difference in paleopoles suggests that sufficient time elapsed for continental motion to occur between deposition of the lower members of the Morrison Formation and the Brushy Basin Member above them.

Arizona, Colorado, New Mexico, Utah↗
USGS1992

Preliminary results of the U.S. Geological Survey-Iowa Department of Natural Resources Geological Survey Bureau Manson Core Drilling Project

The U.S. Geological Survey and Iowa Department of Natural Resources Geological Survey Bureau completed, in 1992, a two-year core drilling program in the Manson Impact Structure, a 35-km-diameter, Cretaceous-Tertiary boundary-age feature located in north-central Iowa. A total of 12 cores sampled in excess of 1,200 m (4,000 ft) of crater rocks, supplementing the two previously drilled shallow cores from the structure. The cores penetrated the three major terranes in the Manson Impact Structure, the terrace terrane, crater moat, and central peak. Preliminary interpretations identified several important impact-related lithologies in these cores. The most widespread is sedimentary clast breccia, a postimpact polymictic breccia or mixtite that mantles at least part of all crater terranes. Two types of crystalline clast breccias were cored on the central peak, one with a melt matrix, the other with a matrix dominated by silt- to sand-sized grains. Large blocks of basement gneiss that formed the interior of the central peak were encountered in several cores. Within the terrace terrane, structurally preserved Cretaceous strata and an overturned ejecta flap of Proterozoic and Paleozoic sedimentary rocks were encountered. Only sedimentary clast breccia was encountered in the crater moat. The preliminary investigation of these cores has provided significant information on the geometry and history of the Manson Impact Structure, but it has also prompted many more questions.

Iowa↗
USGS1990

Asteroid and comet flux in the neighborhood of Earth

Approximately 90 Earth-crossing asteroids had been discovered through September 1989. Discovery is thought to be complete at absolute V magnitude (H) = 13.2 (the magnitude of the brightest known object, diameter ∼8.1 km), and about 6 percent complete at H = 17.7 (typical diameter about 1 km). The calculated mean probability of collision of Earth-crossing asteroids with Earth is (4.2 ± 1.7) × 10 −9 yr −1 . When multiplied by the estimated population of 1030 ± 470 at H = 17.7, this probability yields a collision rate of (4.3 ± 2.6) × 10 −6 yr −1 for asteroids larger than about 1 km in diameter. At H = 15.8, roughly equivalent to asteroid diameters more than 2 km, the estimated collision rate is ≈7 × 10 −7 yr −1 , and at 8-km diameter, the rate is ≈3 × 10 −9 yr −1 . Comet nuclei with diameters more than 2.5 km are estimated to strike the Earth at the rate of ≈ 10 −7 yr −1 ; comets larger than 10 km in diameter probably strike at a rate ≈10 −8 yr −1 . Impact of asteroids probably dominates the production of craters smaller than 30 km in diameter, whereas comet impact probably forms most craters larger than 50 km. The production rate for craters larger than 20 km in diameter, estimated from the astronomical evidence, is (4.9 ± 2.9) × 10 −15 km −2 yr −1 ; this rate is consistent with the cratering rate estimated by Grieve from the geologic record for the last 120 m.y.

Special Papers of the Geological Society of Americ↗
USGS1987

Remanent magnetization of rocks of latest Cretaceous and earliest Tertiary age from drill core at York Canyon, New Mexico

At the end of 1980, seven complete cores were recovered from a 30-m (100-ft) interval in the Raton Formation at York Canyon, New Mexico. The interval cored spans the palynologically defined Cretaceous-Tertiary boundary, which is marked by a distinctive noble metal–bearing claystone in the Raton basin. Azimuthal orientation of the cores can be recovered both from the average directions of the most stable components of the remanent magnetization, with a root mean square error of 28°, and from the average direction of secondary components of magnetization removed by thermal and alternating field demagnetization, with a root mean square error of 33°. The natural remanent magnetization of about 95 percent of the core is dominated by a secondary normal polarity component. Polarity of the characteristic magnetization of each core, interpreted from 12 to 14 samples per core run, is reversed. No evidence of normal polarity characteristic magnetization was found in the 30-m (100-ft) interval sampled. The characteristic magnetization probably is a depositional remanent magnetization acquired during chron 29r. The noble metal–bearing boundary claystone in the Raton basin is interpreted to be part of a synchronous global deposit laid down at the end of the Cretaceous period.

New Mexico↗
USGS1987

Comet showers as a cause of mass extinctions

If at least some mass extinctions are caused by impacts, why do they extend over intervals of one to three million years and have a partly stepwise character? The solution may be provided by multiple cometary impacts. Astronomical, geological and palaeontological evidence is consistent with a causal connection between comet showers, clusters of impact events and stepwise mass extinctions, but it is too early to tell how pervasive this relationship may be.

Nature↗
USGS1982

Collision of astronomically observable bodies with the Earth

There are at present about 1,000 Earth-crossing bodies of asteroidal appearance that have diameters greater than 1 km. It is calculated that on the average about 3 of these bodies impact the Earth every million years. Because there are many more small bodies than large ones, impacts of 10-km-diameter objects, as postulated by Alvarez and others to explain the Cretaceous/Tertiary extinction, occur less frequently. Nevertheless, it is expected that the frequency of impact of these larger bodies will be about once every 40 million years. The cratering record on the Earth and the Moon is in agreement with this estimate. It is likely that bodies as large as 20 km in diameter have struck the Earth during the last 3 billion years. A somewhat smaller but possibly comparable impact rate of active comet nuclei of similar size is also expected. The bodies of asteroidal appearance represent a quasi-steady-state population. Losses by collision and perturbation out of the solar system are balanced by supply on a 10 7 to 10 8 year time scale of new objects: asteroidal fragments and extinct comet nuclei. The relative importance of these two sources is at present uncertain.

Special Papers of the Geological Society of Americ↗
USGS1981

Survey for bright Mars-crossing asteroids

A new method of search for relatively bright Mars-crossing asteroids with the Palomar 46-cm Schmidt camera was initiated in 1980. Selected fields photographed with the 46-cm Schmidt were systematically reduced for all asteroids detected on the films. The 46-cm Schmidt fields have an effective diameter of 8 3/4 degrees. Kodak 11a-D film was exposed with a yellow plexiglass filter. The films were scanned with a specially designed stereomicroscope that permits recognition of asteroids by stereopsis. Stereoscopic pairs of films were exposed with a time separation of 30 minutes; over this interval the parallax in position relative to the background stars allows easy recognition of asteroids at distances ranging from near the Earth through the main belt. Optimum exposure for each film was found to be 10 minutes on the f/2 Schmidt.

Book chapter↗
USGS1978

Bright Angel and Mesa Butte fault systems of northern Arizona

Regional geologic mapping using pictures from the first Earth Resources Technology Satellite (ERTS-1) has led to the recognition of two parallel northeast-trending systems of normal faults, each of which can be traced more than 100 km. Many eruptive centers appear to be localized along these fault systems or along their extensions. The faults are chiefly observed in Phanerozoic rocks and have minor displacement but are interpreted by us to reflect fault zones of major displacement in the crystalline Precambrian basement. The Bright Angel fault system extends as a continuous zone of normal faults from Cataract Creek on the southwest to the Echo Cliffs on the northeast. Beyond the Echo Cliffs, the system continues northeastward to the vicinity of Monument Valley as a more diffuse, discontinuous zone of normal faults. The Bright Angel fault, Vishnu fault, and Eminence Break graben are among the larger individual members of the total system. The Navajo mountain intrusive center lies along the discontinuous part of the system. Three major eruptive centers of the Mount Floyd volcanic field lie on the southwestern projection of the Bright Angel fault system. If the eruptive centers are included as part of the recognizable structural system, the Bright Angel system has a total known length of slightly more than 300 km. The Mesa Butte fault system, as now recognized, extends from Chino Valley on the southwest to Shadow Mountain on the northeast. Bill Williams Mountain, Sitgreaves Peak, and Kendrick Peak are principal silicic to intermediate eruptive centers of the San Francisco volcanic field that appear to be localized along the fault system. Red Mountain, Mesa Butte, and Shadow Mountain are prominent basaltic eruptive centers along the system; monchiquite diatremes at Tuba Butte and Wildcat Peak lie on the northeast projection of the fault system. The total distance from Chino Valley to Wildcat Peak is more than 200 km. Comparison of the Bright Angel and Mesa Butte fault systems with a residual aeromagnetic map of Arizona reveals a close correspondence between the positions of the observed relatively minor normal faults and the margins of a series of large northeast-trending magnetic anomalies. Perhaps the most noteworthy feature of the aeromagnetic map is a 400-km-long northeast-trending belt of large positive aeromagnetic anomalies that extends from the vicinity of Congress to the northern border of Arizona. The Mesa Butte fault system lies along the southeast margin of this anomaly belt. Another large positive anomaly, bounded on the southeast by the Bright Angel fault, corresponds in the Grand Canyon to a belt of Precambrian amphibolite and schist. Most of the large positive aeromagnetic anomalies along the Bright Angel and Mesa Butte fault systems may correspond to similar bodies of mafic metavolcanic rocks, which have been offset along two major and perhaps several minor faults of Precambrian age. The normal faults that displace the overlying Phanerozoic rocks have been formed by renewed movement along these ancient fault zones, in response to dilation of the crust from late Tertiary time to the present. The ancient fault zones inferred to be present along the Bright Angel and Mesa Butte fault systems may be related in origin to the Shylock and Chaparral fault zones in central Arizona described by Anderson (1967). Both the Shylock fault zone and the Chaparral fault have right-lateral transcurrent displacement. As shown by Anderson, the Shylock zone has a probable minimum horizontal displacement of 8 km. A large contrast in the magnetic properties of the rocks on opposite sides of the fault zone, indicated by the aeromagnetic map, suggests that the displacement may be several tens of kilometres or more. Comparably large right-lateral displacements may have occurred along the ancestral Bright Angel and Mesa Butte fault zones. The location of epicenters of recent earthquakes and reports of earthquakes by residents in the region indicate that the Bright Angel and Mesa Butte fault systems are currently active.

Arizona↗